ACUS48 KWNS 280902
SWOD48
SPC AC 280900

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0400 AM CDT Sun Jul 28 2024

Valid 311200Z - 051200Z

...DISCUSSION...
A broad, low-amplitude mid-level ridge is expected to break down on Day4/Wednesday and Day5/Thursday. This may result in some severe
weather across portions of the Midwest. Late this week and into the
weekend, ridging will amplify across the western CONUS. Depending on
the exact evolution of the building upper-level trough, some severe
weather threat may persist across the northern Plains. However, an
area of high pressure is expected to move south out of Canada over
the weekend and scour the higher quality moisture which should
result in less instability than early this week.

...D4/Wednesday and D5/Thursday - Midwest...
Uncertainties remain in the exact evolution of the upper-level ridge
breakdown on Wednesday and Thursday which may significantly impact
the location and intensity of any severe weather threat. A reservoir
of strong instability and steep lapse rates is expected in the
Midwest/Upper Midwest with increasing mid-level flow across the
region. Where storms develop within this environment, severe weather
is likely. However, aforementioned uncertainties preclude the need
for severe weather probabilities at this time.

..Bentley.. 07/28/2024

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ACUS48 KWNS 290827
SWOD48
SPC AC 290826

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0326 AM CDT Mon Jul 29 2024

Valid 011200Z - 061200Z

...DISCUSSION...
A mid-level trough, likely near the Upper Midwest Thursday morning,
will slowly move east through the end of this week and the weekend
as a large amplitude ridge builds over the western CONUS. This slow
moving trough will be the primary feature associated with potential
severe weather during the extended forecast period.

On D4/Thu, a large cluster of storms will likely be ongoing in the
western Great Lakes in response to the forcing from the mid-level
trough and moderately strong isentropic ascent. A very moist airmass
(mid 70s dewpoints) will likely remain on the southern/southwest
extent of any ongoing convection. This will likely be the focus for
potential severe weather threat across Illinois/Indiana/Ohio on
Thursday. Strong instability will be present, however shear will be
somewhat weak, except for portions of Illinois where mid-level flow
will strengthen during the late afternoon/evening. There is still
uncertainty regarding the timing and amplitude of this mid-level
trough. Therefore, no severe weather probabilities will be added at
this time.

As the mid-level trough continues east on D5/Fri and into the
weekend, moisture quality, and thus instability, is forecast to
weaken. In addition, the slowing/deamplifying nature of the
mid-level trough will result in weakening mid-level flow. Therefore,
while some isolated/widely scattered severe weather threat may occur
across portions of the eastern CONUS, a more organized severe
weather threat appears unlikely.

..Bentley.. 07/29/2024

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ACUS48 KWNS 300856
SWOD48
SPC AC 300854

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0354 AM CDT Tue Jul 30 2024

Valid 021200Z - 071200Z

...DISCUSSION...
On Friday and into the weekend, a mid-level trough will slow and
eventually stall across the eastern CONUS. Given remnant moisture,
expect widespread thunderstorm activity. However, severe weather
should be limited by weak shear in the region.

A large-amplitude mid-level ridge which is forecast to build across
the western CONUS on Thursday and Friday will start to deamplify
over the weekend as a series of mid-level shortwave troughs traverse
British Columbia and Alberta. The exact evolution of the pattern
over the weekend and beyond remains uncertain. There is consensus
for multiple mid-level troughs to move through the northern CONUS
with at least some lee troughing across the northern Plains. Some
severe weather is possible with any of these passing impulses.
However, uncertainty remains too high at this time for severe
weather probabilities.

..Bentley.. 07/30/2024

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ACUS48 KWNS 310902
SWOD48
SPC AC 310901

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0401 AM CDT Wed Jul 31 2024

Valid 031200Z - 081200Z

...DISCUSSION...
The extended period will begin with a large amplitude upper-level
ridge across the western CONUS. This ridge will gradually breakdown
on Sunday and Monday with more of a flat ridge by the middle of next
week. Persistent northwesterly flow across the Northern Plains/Upper
Midwest during the extended forecast period may result in some
isolated severe weather threat. However, moisture in the Northern
Plains will lack a Gulf of Mexico connection and thus, will likely
be somewhat low quality, at least initially.

Early next week, as lee troughing returns to the Plains and the
low-level jet strengthens, the severe weather threat may increase
somewhat. Overall, upper-level ridging and no clear strong troughs
during the extended period, suggests any severe weather threat that materializes will likely remain somewhat localized this weekend and
early next week.

..Bentley.. 07/31/2024

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ACUS48 KWNS 010849
SWOD48
SPC AC 010848

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0348 AM CDT Thu Aug 01 2024

Valid 041200Z - 091200Z

...DISCUSSION...
The extended forecast period will feature an upper-level ridge
centered near the Continental Divide with northwesterly flow aloft
from the northern Plains to the East Coast. Severe weather may be
possible any day within this corridor within a pocket of remnant
moisture along/near the frontal zone across the region, and shear
which would support organized severe weather. However, the pocket of instability is relatively narrow given a drier, more continental
airmass so the south of this frontal zone with persistent northerly
flow and a lack of a consistent Gulf moisture feed. In addition, any
mid-level shortwave troughs embedded within the northwesterly flow
will be mesoscale in nature and thus, the details cannot be resolved
at this range.

In addition, the Gulf Coast, Florida, and the Georgia/south Carolina
coast will need to be monitored for potential impacts from a
tropical wave which according to the National Hurricane Center,
could develop into a tropical cyclone late this weekend or early
next week. If an organized tropical system does develop, some
severe-weather threat may materialize.

..Bentley.. 08/01/2024

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ACUS48 KWNS 020846
SWOD48
SPC AC 020844

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0344 AM CDT Fri Aug 02 2024

Valid 051200Z - 101200Z

...DISCUSSION...
Medium-range models indicate that mid-level flow across the northern mid-latitudes may trend less amplified by the middle of next week,
as a mid-level low over northern Quebec weakens/redevelops eastward
into the northwestern Atlantic and a prominent high over
northwestern Canada becomes suppressed. As this occurs, it appears
that low-level cooling and drying may advance southward toward the
Southeast and lower Mississippi Valley, beneath generally weak flow
associated with mid/upper ridging.

Developments across the West remain more uncertain, but it does
appear that persistent mid-upper ridging will become suppressed.
While it is possible that large-scale mid-level troughing may evolve
across the Pacific Northwest and Canadian/northern U.S. Rockies
vicinity, it is not clear that this will be accompanied by potential
for more than isolated strong to severe thunderstorm development
across the northern Intermountain region into northern U.S. Rockies.

..Kerr.. 08/02/2024

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ACUS48 KWNS 030902
SWOD48
SPC AC 030900

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0400 AM CDT Sat Aug 03 2024

Valid 061200Z - 111200Z

...DISCUSSION...
Models suggest that seasonably high moisture content will linger in
a plume along/east of a weak mid-level trough/shear axis, offshore
of the northern Atlantic coast into the southern Atlantic coast
vicinity, as northerly flow leads to continued general drying
elsewhere to the east of the Rockies. It appears possible that a
lingering tropical cyclone, initially centered near/offshore of the
southern Atlantic coast at the outset of the period, remains the
primary potential focus for severe weather, and even this may remain
rather limited. Within weak steering flow, the forecast motion of
this system remains somewhat uncertain. Guidance suggests that a
continuing tropical storm may shift back inland across the Carolinas
by Wednesday or Thursday, before tending to migrate
north-northeastward. While it is possible that this may be
accompanied by at least some continuing tornado potential, this risk
seems likely to remain generally low. Severe probabilities are
being maintained at less than 15 percent through this period.

..Kerr.. 08/03/2024

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ACUS48 KWNS 040900
SWOD48
SPC AC 040859

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0359 AM CDT Sun Aug 04 2024

Valid 071200Z - 121200Z

...DISCUSSION...
Medium-range guidance suggests that fairly prominent mid-level
ridging will be maintained through this period across much of the
Southwest and southern Rockies through the southern Great Plains.
Upstream, it appears that mid-level troughing may become established
near the U.S. Pacific coast by next weekend. Otherwise, the
evolution of troughing downstream of a prominent mid-level high
initially shifting across the Canadian Northwest Territories is more
unclear. Some amplification may eventually contribute to the
northeastward acceleration of the remnants of Debby, near/ahead of a southeastward advancing cold front, after the lingering low-level
circulation center likely shifts back inland across coastal areas
into the southern South Carolina vicinity by Thursday. If this were
to occur, it probably would be accompanied by at least some risk for
convection capable of producing tornadoes into the Mid Atlantic
coast vicinity. However, it is not clear that this potential will
support more than low severe probabilities, and severe weather
elsewhere across the U.S. still appears likely to remain limited
through this period.

..Kerr.. 08/04/2024

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ACUS48 KWNS 050855
SWOD48
SPC AC 050853

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0353 AM CDT Mon Aug 05 2024

Valid 081200Z - 131200Z

...DISCUSSION...
Latest (05/00z) ECENS/GEFS output suggests than an initially
prominent mid-level ridge over the Canadian Northwest Territories
will gradually become suppressed, with the center of higher heights
shifting east-southeastward toward northern Manitoba through early
this weekend. Preceding this feature, it appears that a significant
positively tilted trough will pivot through northwestern Ontario and
the upper Great Lakes, before digging through the lower Great Lakes
and upper Ohio Valley vicinity. As this occurs, it appears that
Debby's remnant lower/mid-level circulation will finally accelerate northeastward out of the Southeast, and offshore of the Mid Atlantic
coast by next weekend. While it might not be out of the question
that this could occur in a manner supportive of an appreciable
increase in potential for convection capable of producing tornadoes
across parts of the Carolinas, Virginia and Delmarva Peninsula
vicinity, probabilities for this still seem generally low at this
time.

Otherwise, modest westerly to northwesterly mid/upper flow
developing across the northern Rockies into northern and central
U.S. Great Plains, around the periphery of a prominent ridge
shifting from the Four Corners into southern Great Plains, may be
conditionally supportive of organized convective development through
much of the period. However, guidance continues to generally
indicate that seasonably modest destabilization will tend to limit
the severe weather potential.

..Kerr.. 08/05/2024

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ACUS48 KWNS 060900
SWOD48
SPC AC 060859

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0359 AM CDT Tue Aug 06 2024

Valid 091200Z - 141200Z

...DISCUSSION...
Medium-range guidance indicates that a significant mid-level trough
and embedded cyclonic circulation, evolving near the Upper
Midwest/Great Lakes region by the beginning of the period, will
progress eastward across much of the Northeast by late this weekend.
As this occurs, it appears that the remnants of Debby will
accelerate into and northeast of the northern Mid Atlantic region on
Saturday.

Although the degree of interaction between these features remains
unclear, significant strengthening of southerly
lower/mid-tropospheric flow appears possible within a plume of
tropical moisture advecting northward in advance of deepening
surface troughing, across the northern Mid Atlantic and
Hudson/Champlain Valleys through New England Saturday through
Saturday night. Warm mid-levels likely will limit deep-layer
instability; but low-level buoyancy, forcing for ascent and shear
might become conducive to organizing low-topped convection. In the
presence of mean cloud-bearing layer flow possibly on the order of
40-50+ kt, and boundary-layer dew points in the lower/mid 70s,
damaging wind gusts and perhaps a few tornadoes will be possible if
this scenario unfolds. Due to lingering uncertainties, severe
probabilities are being maintained at less than 15 percent. But
this could change in later outlooks for this coming Saturday.

..Kerr.. 08/06/2024

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ACUS48 KWNS 070902
SWOD48
SPC AC 070900

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0400 AM CDT Wed Aug 07 2024

Valid 101200Z - 151200Z

...DISCUSSION...
Medium-range guidance indicates that the initially prominent
higher-latitude mid-level ridging emerging from the Canadian
Northwest Territories will gradually become suppressed through this
period. Although there is notable spread concerning the downstream acceleration of the initially significant mid-level low to its
southeast, it appears that larger-scale mid-level troughing will
slowly shift eastward in positively tilted fashion, through the St.
Lawrence Valley and lower Great Lakes region by late this coming
weekend, through the Northeast and Canadian Maritimes by the middle
of next week.

In advance of the troughing, Debby's remnant surface low may
interact with a surface cold front advancing to the east of the
lower Great Lakes/upper Ohio Valley, before perhaps merging into the
primary surface cyclone across southern Quebec by Saturday. Models
have varied concerning these developments, but tropical pre-frontal
moistening in the presence of intensifying deep-layer southerly wind
fields might be accompanied by an evolving low-topped convective
band with potential to produce damaging wind gusts near/east of the Hudson/Champlain Valleys through New England. Due to lingering
uncertainties severe probabilities are begin maintained at less than
15 percent, but this could change in later outlooks for Saturday.

Otherwise, the potential for severe weather elsewhere across the
U.S. late this coming weekend into the middle of next week appears
likely to be remain limited by the lack of stronger boundary-layer destabilization.

..Kerr.. 08/07/2024

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ACUS48 KWNS 080858
SWOD48
SPC AC 080856

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0356 AM CDT Thu Aug 08 2024

Valid 111200Z - 161200Z

...DISCUSSION...
Medium-range model output exhibits considerable spread concerning
short wave developments within the evolving mid/upper flow through
this period. In general, though, it appears that an initially
significant, positively tilted mid-level trough will become
increasingly sheared while progressing through a confluent regime
across and east of the North Atlantic Seaboard late this coming
weekend into early next week. In its wake, generally weak zonal
flow across the U.S. may undergo some amplification by the middle to
later portion of next week, including rising mid-level heights to
the lee of the Rockies, downstream of digging mid-level troughing
near the Pacific coast.

As this regime evolves, boundary-layer dew points are likely to
gradually increase beneath the mid-level ridge, probably back into
the 70s F across parts of the lower through middle Missouri Valley.
Across the middle Missouri Valley, perhaps into lower Missouri
Valley, it appears that this may occur beneath an east-southeastward
advecting plume of warm elevated mixed-layer air, which may
contribute to increasing probabilities for mixed-layer CAPE in
excess of 2000 J/kg by next Wednesday or Thursday.

While there may be some potential for strong thunderstorm activity,
initiating to the lee of the northern Rockies and Front Range, to
grow upscale and organize while progressing into this environment,
this likely will hinge on forcing accompanying sub-synoptic
perturbations progressing around the ridge. Given the
low-predictability of these features at this extended time frame,
severe probabilities still appear generally low through this period.

..Kerr.. 08/08/2024

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ACUS48 KWNS 090820
SWOD48
SPC AC 090819

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0319 AM CDT Fri Aug 09 2024

Valid 121200Z - 171200Z

...DISCUSSION...
In mid/upper levels, a zonally elongated anticyclone will build
laterally from the southern Plains into the Southwest and Gulf Coast
region through much of the day-4-8 period. A general weakness in
heights should persist over parts of CA and the lower Colorado River
Valley region -- intermittently connected to northern-stream
troughing over the Pacific Northwest and western Canada, and to the
subtropical easterlies over MX. Low-amplitude mean ridging should
build northward across the Rockies to the northern Rockies/northern
High Plains region, but based on deterministic GFS/ECMWF and their
ensembles, not intense enough to preclude penetration by a series of
mostly low-amplitude/low-predictability shortwaves emanating from
the Northwest troughing.

Downstream, zonal to northwesterly and largely difluent flow will
prevail over much of the northern Plains, Midwest, Great Lakes, and
Ohio Valley. Even after the southeastern Canada/northeastern CONUS
synoptic trough departs the region day-4, the preceding frontal zone
will remain well-removed to the south, across the southeastern CONUS
to Missouri Valley, as a series of trailing shortwaves reinforce
somewhat lower-amplitude troughing in the Great Lakes and Northeast.
Especially from about day 5 onward, gradual return of favorable
moisture is likely beneath the southwestern rim of the stronger
associated flow -- from the north-central High Plains to the lower
Missouri and Tennessee Valley regions. This general pattern
conditionally supports some MCS potential, evolving from activity
forming over the Plains and heading southeastward along or just to
the cool side of the sensible baroclinic zone. However, day-to-day
shortwave, low-level boundary and MCV predictability is too low to
assign unconditional probabilities to any given day.

..Edwards.. 08/09/2024

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ACUS48 KWNS 100835
SWOD48
SPC AC 100834

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0334 AM CDT Sat Aug 10 2024

Valid 131200Z - 181200Z

...DISCUSSION...
Upper ridging should generally prevail over parts of the Rockies
into the Plains through much of the extended forecast period.
Periodic suppression of the upper ridge should occur as multiple
weak mid-level perturbations move eastward across the
northern/central portions of the CONUS. Isolated strong to severe
thunderstorm potential may exist across parts of the
northern/central Plains into the mid MS Valley and Midwest with any
of these low-amplitude shortwave troughs. For Day 4/Tuesday, the
best severe potential may focus over the northern/central High
Plains along/east of a weak surface trough. However, both
instability and shear appear too limited to include a 15% severe
area. Details on convective evolution become less clear from midweek
onward. But, there are some indications that a shortwave trough may
move across parts of the Plains into the Midwest/mid MS Valley. Even
so, both predictability and forecast strength/amplitude of this
feature remain far too low for any severe probabilities.

..Gleason.. 08/10/2024

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ACUS48 KWNS 110850
SWOD48
SPC AC 110848

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0348 AM CDT Sun Aug 11 2024

Valid 141200Z - 191200Z

...DISCUSSION...
Multiple mid-level perturbations should move eastward across the northern/central CONUS from the middle of this week through next
weekend. This should generally act to suppress upper ridging to the
southern states through at least Day 5/Thursday. Low predictability
for organized severe potential remains apparent in this flow regime
given the low-amplitude nature of relevant features. But,
medium-range guidance shows a tendency for a more amplified pattern
by late week into the upcoming weekend as an upper trough/low
potentially develops across the western states, ridging builds over
the central CONUS, and a separate upper trough/low remains over the
eastern CONUS. Regardless of these developments, isolated severe
potential may exist on Day 4/Wednesday across parts of the
northern/central Plains and perhaps Upper Midwest in association
with one of the mid-level perturbations. Some threat for organized
severe thunderstorms will probably continue each day through the
extended forecast period across parts of the Plains into the Midwest
and vicinity, although delineating regions of greater potential
remains highly uncertain.

..Gleason.. 08/11/2024

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ACUS48 KWNS 120847
SWOD48
SPC AC 120845

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0345 AM CDT Mon Aug 12 2024

Valid 151200Z - 201200Z

...DISCUSSION...
Medium-range guidance is in reasonably good agreement that another
weak mid-level shortwave trough will move eastward across the
northern/central Plains to the Upper Midwest on Day 4/Thursday. Some
severe potential may accompany this feature, but forecast deep-layer
shear should tend to remain rather marginal. Differences also exist
in where a greater severe threat may develop across these regions,
so a 15% severe area has not been included. Gradual amplification of
the upper pattern should occur late this week into the upcoming
weekend, with a trough/low developing over the eastern Pacific,
ridging building over much of the western states into the
Rockies/Plains, and troughing over the East. This pattern may
support isolated severe potential each day from Day 5/Friday through
early next week across parts of the central/eastern CONUS, generally along/south of a weak front and in a northwesterly mid-level flow
regime between the upper ridge and eastern states upper trough.
However, predictability of potential MCS corridors and greater
severe potential remain low at this extended time frame.

..Gleason.. 08/12/2024

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ACUS48 KWNS 130845
SWOD48
SPC AC 130844

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0344 AM CDT Tue Aug 13 2024

Valid 161200Z - 211200Z

...DISCUSSION...
Upper ridging over the southern tier of the CONUS should be
suppressed by a slow moving upper trough/low over the Upper Midwest
and Great Lakes on Day 4/Friday. Moderate to locally strong
instability should once again be in place along/ahead of a weak
front. Sufficient mid-level flow and related deep-layer shear should
exist to support at least an isolated severe threat across parts of
the OH Valley/Midwest into the mid MS Valley and southern/central
Plains. However, the presence of prior convection and only weak
low-level convergence along the front lend low confidence in
delineating a corridor of greater severe potential across these
regions Friday afternoon/evening. Have therefore not included a 15%
severe area at this time.

For this weekend into early next week, an upper low should develop
and remain over the eastern Pacific, off the Northwest Coast. Upper
ridging is forecast to build over much of the West and
Rockies/Plains, with upper troughing persisting over the eastern
states. Some severe threat may continue each day across parts of the
Plains into the Southeast and eastern states, along and south/east
of a weak front. But, the overall synoptic pattern suggests limited predictability in highlighting focused areas of greater severe
potential.

..Gleason.. 08/13/2024

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ACUS48 KWNS 140858
SWOD48
SPC AC 140856

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0356 AM CDT Wed Aug 14 2024

Valid 171200Z - 221200Z

...DISCUSSION...
Medium-range guidance remains in good agreement that upper ridging
will remain prominent, and probably further amplify, over much of
the Rockies/Plains this weekend into early next week. An upper
trough should progress slowly eastward from the Midwest/OH Valley to
the eastern states on Day 4/Saturday. While an isolated severe risk
may exist across parts of the Mid-Atlantic into the Southeast ahead
of a weak front, the overall environment currently appears too
marginal given modest deep-layer shear to warrant inclusion of a 15%
severe area for Saturday. Otherwise, an upper trough/low should
mostly remain off the coast of the Pacific Northwest through at
least early next week, before possibly advancing inland towards the
end of the forecast period (around Day 8/Wednesday). There is a fair
amount of uncertainty regarding potential suppression of the upper
ridge early next week. Regardless, the severe threat across the
CONUS may tend to remain fairly isolated in this time frame, with
the exception of potential MCS development from parts of the Plains
into the Midwest/OH Valley in a northwesterly mid-level flow regime.
But, predictability remains far too low to include any areas early
next week.

..Gleason.. 08/14/2024

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ACUS48 KWNS 150858
SWOD48
SPC AC 150856

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0356 AM CDT Thu Aug 15 2024

Valid 181200Z - 231200Z

...DISCUSSION...
As an upper trough moves slowly eastward over the eastern CONUS, an
isolated severe threat may continue on Day 4/Sunday across parts of
the Mid-Atlantic into the Southeast along/ahead of a cold front.
However, the potential stabilizing effects of prior convection,
along with generally modest deep-layer shear, render low confidence
in a more organized severe/damaging wind threat on Sunday. Lower
severe potential is anticipated across the eastern states on Day
5/Monday as the upper trough progresses eastward and the cold front
moves mostly offshore. Upper ridging will likely remain prominent
across much of the Rockies and Plains through at least early next
week, while an upper trough/low generally remains centered off the
coast of the Pacific Northwest. Some chance for severe thunderstorms
may exist over interior portions of the Northwest into parts of the
northern Rockies/Plains and perhaps Upper Midwest next week. But, predictability of various mid-level perturbations that may encourage
robust thunderstorms remains low at this extended time frame.

..Gleason.. 08/15/2024

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ACUS48 KWNS 160845
SWOD48
SPC AC 160844

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0344 AM CDT Fri Aug 16 2024

Valid 191200Z - 241200Z

...DISCUSSION...
...Monday/Day 4 to Wednesday/Day 6...
An upper-level ridge is forecast to remain over the High Plains from
early to mid week, as an upper-level trough moves slowly eastward
across the eastern U.S. Surface high pressure, associated with the
trough is forecast to move from the middle to upper Mississippi
Valley on Monday to the middle and upper Atlantic Seaboard by
Wednesday. Due to this high, the airmass across much of the eastern
third of the U.S. will likely become drier and less unstable from
Monday to Wednesday, making conditions less favorable for severe
storms.

Further to the west, a south-to-north corridor of moderate
instability is forecast to develop each day, remaining in a similar
position across the central and northern Plains. Thunderstorms will
be possible each afternoon and evening to the east of the ridge near
the axis of instability. It appears that deep-layer shear will be
relatively weak near instability axis, which will favor less storm organization. Still, a marginal severe threat will be possible due
to the strong instability.

...Thursday/Day 7 and Friday/Day 8...
The upper-level ridge in the north-central U.S. is forecast to move
eastward from the northern Plains on Thursday into the western Great
Lakes region by Friday. An axis of moderate to strong instability is
forecast to remain over the central and northern Plains.
Thunderstorms that form each afternoon close the instability axis
will have a chance be severe. Although there is a lot of uncertainty
this far out in the forecast cycle, the subsidence and weaker
deep-layer shear associated with the upper-level ridge, should
negatively impact severe potential. However, instability could be
strong enough for a marginal severe threat, mainly during the
afternoon and evening on Thursday and Friday.

..Broyles.. 08/16/2024

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ACUS48 KWNS 170902
SWOD48
SPC AC 170900

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0400 AM CDT Sat Aug 17 2024

Valid 201200Z - 251200Z

...DISCUSSION...
...Tuesday/Day 4 to Thursday/Day 6...
A shortwave ridge over the eastern part of the northern Plains is
forecast to deamplify on Tuesday. Further west, the large-scale
upper-level ridge is forecast to move eastward across the northern
Plains on Tuesday and into the upper Mississippi Valley from
Wednesday into Thursday. This feature will move away from a moist
axis in the northern Plains, where moderate instability is forecast
each afternoon. Thunderstorm development, some with potential for
isolated large hail and severe wind gusts, will be possible each
day. The greatest severe threat during the mid-week is expected on
Wednesday in the Dakotas, where southwest mid-level flow and strong
instability is forecast in the wake of the upper-level ridge.

...Friday/Day 7 and Saturday/Day 8...
On Friday, some model solutions deepen an upper-level trough over
the Intermountain West. In response, the north-central U.S
upper-level ridge would move eastward toward the western Great
Lakes. Isolated thunderstorms, possibly associated with a severe
threat, would be possible within a moist airmass located further to
the west from Nebraska into the Dakotas. However, some solutions are
slow to move the upper-level trough into the western U.S. This would
keep the upper-level ridge further west, negatively impacting the
severe potential across the northern Plains. Under this scenario,
storm coverage would be more isolated and the severe threat would
not be as great.

..Broyles.. 08/17/2024

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ACUS48 KWNS 180851
SWOD48
SPC AC 180850

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0350 AM CDT Sun Aug 18 2024

Valid 211200Z - 261200Z

...DISCUSSION...
...Wednesday/Day 4 to Friday/Day 6...
An upper-level ridge is forecast to gradually deamplify, moving from
the northern Plains on Wednesday to the Great Lakes on Friday. An
axis of instability will likely remain in the central and northern
Plains from mid to late week, where isolated to scattered
thunderstorms are expected to develop each afternoon and evening.
The strongest instability is forecast over the Dakotas on Wednesday,
with the ECMWF having SBCAPE peak above 4000 J/kg along the
instability axis. This, combined with 0-6 km shear in the 30 to 40
knot range, would support isolated supercell development. Large hail
and severe wind gusts would be the primary threats. However, some
solutions suggest that the upper-level ridge will be slower to move
eastward, which would keep convection more isolated on Wednesday.
For this reason, will not add a threat area for Wednesday. A similar
setup is forecast on Thursday and Friday, which would support a
marginal severe threat across the northern Plains each afternoon and
evening.

...Saturday/Day 7 and Sunday/Day 8...
On Saturday, some of the medium-range models have an upper-level
trough moving through the northern Rockies and Intermountain West. Southwesterly flow would be in place across much of the
north-central U.S. Ahead of this feature, scattered thunderstorm
would be possible across parts of the northern High Plains and
Dakotas. Under this scenario, which is favored by the ECMWF, severe
storms would be possible in parts of the northern Plains extending south-southeastward along the instability axis into the mid Missouri
Valley. The severe threat would be shifted eastward into the parts
of the upper Mississippi Valley on Sunday. For the weekend, other
models are considerably slower with the progression of the western
U.S. upper-level trough, which adds a lot of forecast uncertainty.

..Broyles.. 08/18/2024

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ACUS48 KWNS 190853
SWOD48
SPC AC 190851

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0351 AM CDT Mon Aug 19 2024

Valid 221200Z - 271200Z

...DISCUSSION...
...Thursday/Day 4 to Saturday/Day 6...
An upper-level ridge is forecast to gradually build over the Great
Plains from Thursday to Saturday. During this time period, an axis
of low-level moisture and instability is forecast to remain over the
central and northern Plains. As surface temperatures warm each day,
isolated thunderstorms are expected to develop over parts of the
moist airmass. Moderate deep-layer shear and steep lapse rates
should be favorable for a severe threat, with large hail and severe
wind gusts possible. However, large-scale ascent and the resultant
convective coverage is forecast to be limited, which should reduce
the overall severe threat coverage.

...Sunday/Day7 and Monday/Day 8...
An upper-level low over the Desert Southwest is forecast by the
ECMWF to move quickly northeastward across the Intermountain West on
Sunday, and into the northern Plains on Monday. Ahead of this
feature, the medium range models suggest that a broad corridor of
strong instability will be in place. Although convective coverage
may remain relatively isolated on Sunday and Monday, the strong
instability should be favorable for a severe threat. Large hail and
isolated severe wind gusts would be possible in the northern Plains
on Sunday, and in the upper Mississippi Valley on Monday. However,
there is a wide dispersion of solutions concerning the timing of the upper-level trough. This suggest that uncertainty is substantial
from Sunday into Monday. Once the models become in better agreement,
a threat area may need to be considered early next week if it
appears that convective coverage over the warm sector will be
sufficient.

..Broyles.. 08/19/2024

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ACUS48 KWNS 200839
SWOD48
SPC AC 200838

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0338 AM CDT Tue Aug 20 2024

Valid 231200Z - 281200Z

...DISCUSSION...
...Friday/Day 4 to Sunday/Day 6...
Heights within the persistent central U.S. upper-level ridge are
forecast to rise from Friday to Sunday, as a mid-level trough moves
through the western U.S. An axis of maximized low-level moisture and instability is forecast to remain over the central and northern
Plains extending south-southeastward into the mid Missouri Valley.
Thunderstorm development, with a potential severe threat, will be
possible across parts of this unstable airmass each afternoon and
evening. Subsidence associated with the upper-level ridge will be a
negative factor, which is expected to keep the severe threat
isolated and marginal through the weekend.

...Monday/Day 7 and Tuesday/Day 8...
The medium-range models are finally in agreement concerning the
timing of an upper-level trough, which is forecast to move through
the northern Plains on Monday. Ahead of this trough, a moist and
unstable airmass is forecast from the mid Missouri Valley
northeastward into the western Great Lakes. Thunderstorms are
expected to develop ahead of the trough over parts of the Minnesota
and Wisconsin, with more isolated convection southward into Iowa.
Strong instability and moderate deep-layer shear should be favorable
for a severe threat, with the most likely area in the upper
Mississippi Valley Monday afternoon and evening. However, there is
still uncertainty concerning the timing of the trough, and location
of the instability axis on Monday. In addition, part of the airmass
could remain capped. At this point, will not outlook a threat area.
The potential severe threat is forecast to shift eastward into the
central Great Lakes region on Tuesday, but could be isolated due to
the presence of a northeastern U.S. upper-level ridge.

..Broyles.. 08/20/2024

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ACUS48 KWNS 210856
SWOD48
SPC AC 210855

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0355 AM CDT Wed Aug 21 2024

Valid 241200Z - 291200Z

...DISCUSSION...
...Saturday/Day 4 to Monday/Day 6...
Heights within an upper-level ridge are forecast to rise across the
central and northern U.S over the weekend, as an upper-level trough
moves across the western U.S. Isolated severe-thunderstorm
development will be possible across the Dakotas in the afternoon and
evening both Saturday and Sunday. The best chance for severe storms
would be on Sunday as large-scale ascent and deep-layer shear both
increase across the northern Plains due to the approach of the
trough.

The severe threat is forecast to shift eastward into the upper
Mississippi Valley on Monday, as the upper-level trough and its
associated cold front advance eastward from the northern Plains into
the upper Mississippi Valley.

...Tuesday/Day 7 and Wednesday/Day 8...
On Tuesday and Wednesday, the upper-level trough is forecast to
deamplify as it moves through the Great Lakes region. Another
upper-level trough is forecast to move through the western U.S on
Tuesday and Wednesday. The best chance for severe storm development
would be on Wednesday afternoon along an instability axis, most
likely in either eastern parts of the northern Plains or in the
upper Mississippi Valley. At this range, large model spread
concerning the timing of the trough and distribution of instability
suggests uncertainty is substantial.

..Broyles.. 08/21/2024

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ACUS48 KWNS 220901
SWOD48
SPC AC 220900

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0400 AM CDT Thu Aug 22 2024

Valid 251200Z - 301200Z

...DISCUSSION...
...Sunday/Day 4 to Tuesday/Day 6...
Heights within an upper-level ridge over the Mississippi Valley will
continue to rise on Sunday, as an upper-level trough moves through
the western U.S. The ridge is forecast to move into the western
Great Lakes from Monday into Tuesday, as the upper-level trough
moves across the north-central U.S. Ahead of the approaching trough, thunderstorm development will be possible each day, from the
northern Plains into the upper Mississippi Valley. For the three
days, the greatest chance of severe storms appears to be in the
Dakotas on Sunday and in the upper Mississippi Valley on Monday.
Strong instability and moderate deep-layer shear, combined with
increasing large-scale ascent, should result in a severe threat each
afternoon and evening. Large hail and severe gusts will likely be
the primary threats.

...Wednesday/Day 7 and Thursday/Day 8...
On Wednesday and Thursday, the upper-level trough is forecast to
move across the upper Mississippi Valley and into southern Canada,
as a second trough moves through the northern Plains. At the
surface, a moist airmass is forecast to remain in place over the
Great Lakes region and Upper Midwest. Scattered to widely scattered thunderstorms will be possible across much of this moist airmass on
both days. Although an isolated severe threat will be possible each
afternoon and evening, the threat is expected to remain marginal due
to a large area of mid-level high pressure that is forecast to be in
place over much of the eastern half of the nation.

..Broyles.. 08/22/2024

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ACUS48 KWNS 230902
SWOD48
SPC AC 230901

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0401 AM CDT Fri Aug 23 2024

Valid 261200Z - 311200Z

...DISCUSSION...
Models continue to suggest potential for severe weather across parts
of the Upper Mississippi Valley area Day4/Monday, as a mid-level
short-wave trough is shunted northeastward across this region by the
persistent central U.S. ridge. Timing of the advance of this
feature differs between the GFS and ECMWF, casting some uncertainty,
but enough agreement exists to maintain a 15% probability area
across this region.

One other area of interest Day 4/Monday is across portions of the
southern New England/Mid-Atlantic vicinity within a northwesterly
flow regime on the southwestern side of New England/Canadian
Maritimes upper low. Enhanced northwesterlies aloft would be
sufficient to produce rather fast-moving bands of storms, but degree
of instability remains a substantial question at this time. With
intensity of the convection thus still uncertain, will refrain at
this time from introducing a risk area.

As the north-central U.S. mid-level feature moves into/across
Ontario Day 5, a decrease in severe risk is expected despite a weak
frontal advance southeastward across the Great Lakes into the Ohio
Valley.

Beyond Day 5, models begin to deviate substantially, particularly
with respect to their handling of the next trough expected to
progress eastward across the Canadian Prairie and
northwestern/north-central CONUS. While some severe potential could
accompany this feature, particularly if an evolution that resembles
the stronger ECMWF solution plays out, uncertainty precludes any
reasonable assessment of severe potential.

..Goss.. 08/23/2024

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ACUS48 KWNS 240855
SWOD48
SPC AC 240854

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0354 AM CDT Sat Aug 24 2024

Valid 271200Z - 011200Z

...DISCUSSION...
Within the faster belt of upper flow across the northern U.S.,
substantial differences in timing of the disturbances in the flow
are manifest from the very start of the medium-range period. On
Tuesday/Day 4, an energetic short-wave trough should be crossing the north-central U.S., headed toward the Upper Mississippi
Valley/southern Ontario, while an upstream trough crosses western
Canada and the Pacific Northwest, and a downstream one crosses
northern Quebec. However, noted differences in both timing and
orientation of these features is immediately apparent. The
north-central U.S. feature -- the one associated with Day-4 severe
risk over the Great Lakes region -- is roughly 12 hours slower, and
evolves to a more negatively tilted configuration in the ECMWF, as
compared to the GFS. This results in fairly substantial differences
in the surface pattern as well, prohibiting any forecast of the
specifics regarding the severe-weather potential on Tuesday. Still, severe-weather risk is apparent despite east-west geographical
uncertainties. Thus, will introduce an elongated 15% area across
the Upper Midwest and Great Lakes region, given likelihood for
existence of a favorably unstable/amply sheared environment in the
vicinity of a surface front likely to stretch east-northeastward to west-southwestward across this region. Damaging winds and hail
would likely be the primary risks.

By Day 5, differences continue to amplify. Risk for severe weather
may evolve across portions of the Northeast (favored by the GFS),
and/or parts of the Midwest/Ohio Valley (favored by the ECMWF).
However, the differences are substantial enough amongst the models
to preclude an areal highlight at this time. Meanwhile farther
west, an upper low/trough is forecast to be moving across the
northwestern U.S. and Canadian Prairie early in the day, but
location/timing, and intensity differences with this feature are
pronounced. While some severe risk may evolve across parts of the north-central U.S. ahead of this feature and an associated cold
front, the differences preclude any areal outlines at this time.

Predictability issues persist through the remainder of the period,
with model solutions diverging steadily through the upcoming Labor
Day weekend.

..Goss.. 08/24/2024

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ACUS48 KWNS 250900
SWOD48
SPC AC 250859

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0359 AM CDT Sun Aug 25 2024

Valid 281200Z - 021200Z

...DISCUSSION...
Potential for severe weather may spread across parts of the
Northeast/New England Day 4/Wednesday. However non-trivial
uncertainty is evident -- regarding both details with respect to how
the short-wave trough crossing Ontario interacts with the more
pronounced trough shifting eastward across Quebec into the Canadian
Maritimes, as well as evolution/progression of ongoing Day-3
convection. Therefore, despite potential for severe weather that is
evident in a broad/general sense, no areas will be highlighted at
this time.

Upstream, models forecast the advance of an upper low across the
Canadian Prairie, with troughing south of the low to cross the
northern Intermountain Region and eventually reach the northern
Plains. As this system advances, a cold front is progged to move
into/across the Dakotas and western Nebraska diurnally. Amply
strong flow should accompany this trough, along with the likelihood
for sufficient warm-sector destabilization to support storm
development. This suggests some potential for severe weather across
portions of the northern Plains, but -- similar to the potential for
severe weather over the Northeast -- will refrain from any areal
highlights at this time.

Beyond Day 4/Wednesday, model differences steadily increase with
respect to the large-scale features, and thus will refrain from
attempts to assess risk through the remainder of the medium-range
period.

..Goss.. 08/25/2024

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ACUS48 KWNS 260845
SWOD48
SPC AC 260844

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0344 AM CDT Mon Aug 26 2024

Valid 291200Z - 031200Z

...DISCUSSION...
An upper low is forecast to move across the Canadian Prairie and
north-central U.S. through the first half of the Day 4/Thursday
period, before being shunted a bit northeastward into Ontario due to
pronounced downstream ridging. Timing differences amongst the
medium-range global models with the advance of this feature,
similarly result in positional differences with the surface front.
Thus, while some severe risk may manifest during the
afternoon/evening hours across the Upper Midwest region given a likely-to-be-sufficient kinematic and thermodynamic environment
ahead of the front, no risk areas will be highlighted at this time.

Similarly on Day 5/Friday, timing differences are evident as upper
troughing and the associated surface front shift across the Upper
Great Lakes/Midwest region. While some severe risk would again be
possible within this general region, too much positional uncertainty
exists for areal outlines.

Beyond Day 5, a gradual expansion of cyclonic flow aloft is forecast
across roughly the eastern half of the country -- though to
different degrees in the various models. As this occurs, the more
favorably moist low-level airmass will gradually be suppressed
southward, south of the faster belt of flow aloft, and thus a
general decrease in severe risk is expected across the U.S. overall.
This trend should continue through the end of the period, as a
pronounced intrusion of Canadian air gradually spreads across the
eastern two-thirds of the country through Labor Day and beyond.

..Goss.. 08/26/2024

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ACUS48 KWNS 270904
SWOD48
SPC AC 270902

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0402 AM CDT Tue Aug 27 2024

Valid 301200Z - 041200Z

...DISCUSSION...
Latest runs of the global models suggest that the general pattern
evolution over the U.S. through the medium range will be
characterized by a slowly progressive upper flow field, trending
toward amplification of troughing over the eastern U.S. and ridging
over the West. Late in the period, as the pattern continues to
progress, a Pacific trough is progged to approach and then move into
the western states, while the western U.S. ridge shifts gradually
toward the central states. Still farther upstream, the eastern U.S.
trough will likewise continue shifting eastward, into/across New
England and the Canadian Maritimes.

Through the first half of the period, as the upper trough moves
across the Great Lakes region and adjacent Ontario and is then
reinforced by a second feature digging southeastward out of Canada,
a series of surface cold fronts will shift eastward/southeastward
across the central and eastern CONUS.

On Day 4/Friday, at least some severe threat will likely evolve over
the Upper Great Lakes/Midwest, ahead of the initial cold front. By
Day 5/Saturday, convection -- and possibly limited severe risk --
may spread across the Lower Lakes and Ohio Valley area. A
continued, eastward shift should persist through Day6/Sunday, as the
next front accelerates eastward across the Great Lakes/Midwest, with
most substantial strong convective potential evolving from New
England into the Mid-Atlantic region. Overall however, with
low-level moisture begin suppressed gradually southward by Canadian
frontal intrusions, and the surface baroclinic zone settling south
of the stronger flow aloft, overall risk should remain limited, and
gradually decreasing through the period. As such, no risk areas are
being included in the medium-range outlook at this time.

..Goss.. 08/27/2024

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ACUS48 KWNS 280857
SWOD48
SPC AC 280856

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0356 AM CDT Wed Aug 28 2024

Valid 311200Z - 051200Z

...DISCUSSION...
Medium-range global models continue to suggest limited severe
potential Days 4-5 (Saturday and Sunday) largely within the
northeastern quarter of the country, followed by several days of
what appears likely to be minimal severe risk through the remainder
of the period.

Day 4/Saturday, upper-level height falls are progged to shift across
the Great Lakes/Midwest/Northeast, as a strengthening upper trough
advances east-southeastward across Ontario and the Upper Great Lakes
region. A weak cold front will cross the Lower Great
Lakes/Appalachians, with likelihood for showers and thunderstorms
accompanying this front. However, with stronger flow aloft limited
to areas from Pennsylvania northward, where instability should
remain limited, overall severe risk appears at this time to remain
too low to warrant inclusion of a risk area associated with this
frontal passage.

Limited severe potential may also exist for a few hours in the
afternoon and early evening over the Upper Mississippi Valley area,
as a stronger/reinforcing cold front surges southeastward out of
Canada across the Upper Mississippi Valley and Great Lakes region
and into central Plains and Upper Midwest overnight. Though only
modest moisture -- and thus weak afternoon pre-frontal
destabilization -- is expected, low-topped convection is expected
during the afternoon across parts of Upper Michigan/Wisconsin and
perhaps Minnesota. Strong northwesterly flow aloft would support
fast-moving storms, and possibly a risk for damaging winds locally.
Again though, this potential appears too limited/uncertain to
include a risk area at this time.

Day 5, the surging cold front is forecast to shift southeastward
into the Northeast/New England, and southward across the Ohio Valley
area. Similar to Day 4 potential for low-topped storms farther
northwest, convection will likely develop along the front through
the afternoon -- particularly across the New England vicinity.
However, given the frontal passage the prior day, questions with
respect to available moisture -- and thus destabilization potential
-- exist at this time. As such, despite the strong front and strong
flow aloft, severe risk again appears limited and uncertain,
precluding introduction of a risk area for now.

The cold front is expected to have moved offshore of New England and
the Mid-Atlantic region by the start of Day 6, becoming
quasistationary in a west-to-east manner across the Southeast and
Mid South, on the southern fringe of a Canadian High settling into
the northeastern quarter of the country. While convection will
likely occur near and south of this front where moist Gulf air will
remain in place, this region will remain well south of the enhanced
flow aloft. Therefore, severe risk appears minimal -- and should
remain so through the end of the period.

..Goss.. 08/28/2024

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ACUS48 KWNS 290902
SWOD48
SPC AC 290900

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0400 AM CDT Thu Aug 29 2024

Valid 011200Z - 061200Z

...DISCUSSION...
Medium-range/global models are in reasonably good agreement with
respect to synoptic-scale features across the U.S. through about Day
6/Tuesday. Late in the period, models begin deviating with respect
to their handling of an upper low, which through the first half of
the period is progged to be moving in a slow, anticyclonic arc
around northern fringes of a western and central U.S. ridge. As
this feature crests the ridge, moving across the northern
Intermountain region Day 7/Wednesday, model solutions begin to
diverge with respect to progression of the system, with divergence
continuing through Day8. Therefore, while some severe risk may
accompany the advance of this feature toward/into the north-central
U.S. late in the period, uncertainty precludes any further
assessment of this potential.

Meanwhile early in the period, an upper trough will shift across the northeastern quarter of the country Day 4/Sunday. An associated
cold front is progged to advance across the Northeast/Mid-Atlantic
region, but with preceding low-level moisture likely already swept
off the New England Coast by a prior frontal passage. As such, it
appears that only a limited potential for stronger storms will exist
along trailing portions of the front farther south (from the
Mid-Atlantic vicinity westward into the Tennessee Valley area) with
stronger flow aloft remaining farther to the north.

Days 5-6 and beyond, the front will continue sagging southward
across the Southeast and Gulf Coast States, as a Canadian surface
high settles southeastward into the Plains/Great Lakes/Midwest.
While convection can be expected near and south of this boundary,
stronger flow aloft will remain well north of this region, thus
precluding organized severe potential.

..Goss.. 08/29/2024

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ACUS48 KWNS 300837
SWOD48
SPC AC 300835

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0335 AM CDT Fri Aug 30 2024

Valid 021200Z - 071200Z

...DISCUSSION...
Global models appear to be in reasonable agreement through the
medium range, with a long-wave upper trough crossing the eastern
U.S. Day 4/Monday, and then shifting into the Canadian Maritimes and
western Atlantic Day 5/Tuesday. Weak/low-amplitude flow aloft will
prevail across the U.S. Day 5 and into Day 6/Wednesday, before the
pattern begins to amplify again through Days 7-8 (Thursday and
Friday, Sept. 5-6). This amplification anticipated late in the
period will result in an eastern trough/western ridge configuration,
with a cold front to progress across the eastern half of the country
through the second half of the period.

However, with the prior (Day 3) frontal advance across the southern
U.S., and persistence of Canadian surface high pressure in its wake,
rich/Gulf moisture is expected to remain confined to southern
portions of the country. This should limit severe potential with
the late-period system as it crosses the CONUS. As such, no
severe-weather risk areas are being included in the forecast, as
overall potential appears likely at this time to remain low through
the end of the upcoming week.

..Goss.. 08/30/2024

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ACUS48 KWNS 020901
SWOD48
SPC AC 020900

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0400 AM CDT Mon Sep 02 2024

Valid 051200Z - 101200Z

...DISCUSSION...
Global models have come into a bit better agreement with each other,
through late next week, with respect to their handling of the
large-scale features. Day 4 (Thursday), the upper trough crossing
central portions of Canada and the north-central U.S. is progged to
continue digging southeastward -- reaching a roughly upper
Mississippi Valley to Mid-Missouri Valley position by Friday
morning. As this occurs, a corresponding eastward/southward advance
of a surface cold front will occur, crossing the Upper Great
Lakes/Upper Midwest and drifting as far south as the central Plains
overnight. Preceding the front, limited low-level moisture is
expected, with Gulf moisture remaining restricted to the
southern-tier states. Thus, while a few strong/severe storms may
evolve within a southern Upper Great Lakes to central Plains
corridor, potential for a more widespread severe event appears
limited at this time.

Day 5 (Friday), a continued southeastward advance/amplification of
the upper trough is anticipated, shifting across the Great Lakes and
Midwest through the day, and with cyclonic flow surrounding the
trough to encompass the entire eastern half of the country by
Saturday morning. The associated cold front -- crossing the central
U.S. through the day, is expected to reach a Lower Great Lakes to
Lower Mississippi Valley to Texas position overnight. Meanwhile,
the height falls associated with this trough into the southeastern
U.S. may support frontal wave development along the remnant
baroclinic zone likely to be lingering over the northern Gulf/Gulf
Coast area. While still uncertain, this low may shift across the
Southeast Friday, reaching the eastern Carolinas vicinity by Sunday
morning. While it is not out of the question that -- with this
front/low marking the northward extent of tropical low-level air,
that low-end severe risk could evolve overnight. However, this
scenario is uncertain, and would seem likely to remain limited in
terms of significance.

Day 6, some negative tilt of the upper trough is expected as it
advances across the Midwest and Lower Great Lakes area, with models
suggesting evolution into a closed low over the eastern Ontario
vicinity with time. Meanwhile, the advancing cold front is progged
to begin to overtake the remnant baroclinic zone and frontal wave,
with the combined front to linger near -- and eventually move off --
the Atlantic Seaboard as the frontal low moves toward/into southern
New England overnight. Again, some severe potential may manifest
ahead of the consolidating surface front, but at this time, models
suggest that destabilization will remain largely just offshore.

By Sunday (Day 7) and continuing through the end of the period,
model divergence increases -- with evolution/positioning of the
deepening closed low over eastern NOAM, and -- as a result, the
upstream flow pattern over the western half of the country. Overall
severe risk would appear to be low overall however, with general
ridging likely over the western half of the country.

..Goss.. 09/02/2024

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ACUS48 KWNS 030824
SWOD48
SPC AC 030823

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0323 AM CDT Tue Sep 03 2024

Valid 061200Z - 111200Z

...DISCUSSION...
On D4/Friday, on upper-level trough is forecast to amplify as it
digs southeastward across the Great Lakes region. In response, a
surface low is forecast to deepen in the vicinity of the lower Great
Lakes, though the timing and intensity of cyclogenesis continues to
vary among extended-range guidance. Depending on the timing of the
upper-level trough and attendant cold front, strong storms could
develop across parts of the Ohio Valley during the afternoon and
evening as low/midlevel flow strengthens, though generally weak
instability could tend to limit severe potential.

Uncertainty regarding the synoptic evolution on D4/Friday continues
into D5/Saturday. However, there will be some potential for
low-level moisture to be drawn northward into parts of the Mid
Atlantic and Northeast, in advance of the cold front. Instability
may remain quite weak, but rather strong flow could support
convection with gusty-wind potential, if adequate prefrontal
buoyancy can develop.

For D6/Sunday and beyond, most guidance keeps richer low-level
moisture confined near the Gulf Coast, which could generally limit
severe potential across much of the CONUS. One possible exception is
the High Plains vicinity, where modest low-level moisture return
could support some increase in convective potential, especially if a northwesterly flow regime can be maintained between the deep eastern
trough and an upper ridge that may become reestablished near the
Four Corners region. However, predictability regarding synoptic
details begins to substantially wane into early next week.

..Dean.. 09/03/2024

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ACUS48 KWNS 040811
SWOD48
SPC AC 040810

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0310 AM CDT Wed Sep 04 2024

Valid 071200Z - 121200Z

...DISCUSSION...
...D4/Saturday - D5/Sunday: Northeast/Mid Atlantic...
An amplifying trough is forecast to evolve into a rather deep
mid/upper-level cyclone over parts of Ontario into the eastern Great
Lakes region on Saturday, and then begin moving eastward on Sunday.
Uncertainty remains regarding the intensity/location of related
surface cyclogenesis, and the timing of an attendant cold front into
parts of the Northeast and Mid Atlantic. There will be some
potential for low-level moisture to be drawn northward in advance of
the cold front, though instability will likely remain weak. If
adequate buoyancy can develop, then increasing flow fields could
support some increase in severe potential across parts of the Mid
Atlantic and Northeast on D4/Saturday. Uncertainty regarding frontal
position increases into D5/Sunday, though some guidance suggests
potential for frontal convection to develop across parts of New
England before moving offshore.

...D6/Monday - D8/Wednesday...
The deep trough over the eastern CONUS is generally forecast to
weaken and move offshore early next week. Farther west, an upper
ridge is forecast to amplify over the Southwest, while an upper
trough deepens over the eastern Pacific and eventually begins to
impinge upon the Pacific Coast. A persistent surface ridge over the
East is expected to keep richer low-level moisture confined to near
the Gulf Coast, which will tend to limit moisture return and severe-thunderstorm potential across much of the CONUS.

..Dean.. 09/04/2024

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ACUS48 KWNS 050815
SWOD48
SPC AC 050813

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0313 AM CDT Thu Sep 05 2024

Valid 081200Z - 131200Z

...DISCUSSION...
A deep upper-level trough initially over the eastern CONUS on
D4/Sunday is forecast to move offshore early next week. In the wake
of this trough and its attendant cold front, a surface ridge is
expected to persist over much of the eastern CONUS through mid week.
This ridge will likely prevent the northward return of richer
low-level moisture for most of the extended-range period, which
should tend to limit organized severe-thunderstorm potential across
much of the CONUS.

There is some potential for the influence of the eastern surface
ridge to wane by D7/Wednesday into D8/Thursday, while some guidance
suggests a mid/upper-level trough will approach the central/northern
High Plains during this time frame. Should this occur, there could
be some increase in severe potential, though predictability remains
rather low at this forecast range.

..Dean.. 09/05/2024

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ACUS48 KWNS 060853
SWOD48
SPC AC 060852

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0352 AM CDT Fri Sep 06 2024

Valid 091200Z - 141200Z

...DISCUSSION...
...Monday/Day 4 to Wednesday/Day 6...
An upper-level trough is forecast to move from the Northeast into
the Atlantic early in the week, as a shortwave ridge moves through
the Great Lakes. Another shortwave trough is forecast to move
through the north-central U.S. At the surface, a large area of high
pressure is forecast to remain over the eastern third of the U.S.
This will likely impede moisture return over the southern U.S.
through midweek. While thunderstorms will be possible near the Gulf
Coast each day, deep-layer shear is forecast to be too weak for
severe storms. Isolated thunderstorms may also develop each
afternoon in parts of the north-central states, but limited
large-scale ascent and relatively weak deep-layer shear should be
unfavorable for organized storms.

...Thursday/Day 7 and Friday/Day 8...
Low-level moisture is forecast to return northward into the Arklatex
on Thursday, as a shortwave trough moves through the south-central
U.S. Thunderstorm development, with some potentially severe, will be
possible within the moist airmass from the southern Plains eastward
into the lower to mid Mississippi Valley. There is considerable
uncertainty concerning the timing of the shortwave trough and
instability. For this reason, the area with the greatest threat is
unclear at this time. On Friday, moisture advection is forecast to
continue across the central U.S. as the western U.S. upper-level
trough approaches the central and northern Plains. Isolated severe thunderstorms will be possible ahead of the trough in the
north-central states. Uncertainty on Friday is again substantial due
to the relatively wide dispersion among the model solutions.

..Broyles.. 09/06/2024

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ACUS48 KWNS 070854
SWOD48
SPC AC 070853

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0353 AM CDT Sat Sep 07 2024

Valid 101200Z - 151200Z

...DISCUSSION...
...Tuesday/Day 4 to Thursday/Day 6...
A shortwave ridge is forecast to move eastward across the Great
Lakes region on Tuesday and into the Northeast on Wednesday. Another
shortwave ridge is forecast to move through the north-central U.S.
on Wednesday as an upper-level trough amplifies across the western
U.S. Due to the presence of instability in the northern Plains,
thunderstorm development will be possible each afternoon. However,
large-scale ascent is expected to be limited and deep-layer shear
relatively weak, suggesting that storms should remain isolated and
unorganized. Additional storms will be possible near the Gulf Coast
each day.

...Friday/Day 7 and Saturday/Day 8...
The western U.S. upper-level trough is forecast to move through the
Rockies and into the north-central states from Friday into Saturday.
As the trough moves out, large-scale ascent is forecast to
overspread a moist and unstable airmass in the northern and central
Plains. Although some severe threat will be possible ahead of the
trough, deep-layer shear is forecast to be relatively weak. This
suggests that any severe threat that develops during the afternoon
and evening should remain isolated.

..Broyles.. 09/07/2024

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ACUS48 KWNS 080852
SWOD48
SPC AC 080850

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0350 AM CDT Sun Sep 08 2024

Valid 111200Z - 161200Z

...DISCUSSION...
...Wednesday/Day 4 to Friday/Day 6...
An upper-level ridge is forecast to move across the north-central
U.S. on Wednesday, as a trough develops in the western U.S. An
upper-level low is forecast to move across the northwestern states
from Wednesday to Friday. Ahead of the trough, thunderstorms will be
possible each day from the Intermountain west eastward into the
central and northern Plains. At this time, the potential for severe
may be limited by instability, which is generally forecast to remain
weak across most of the western and central U.S.

In the Gulf Coast region, some model forecasts have a tropical
system becoming organized in the northern Gulf from Wednesday to
Friday. If this system materializes and can move onshore, the day
with the greatest potential to impact the central Gulf Coast would
be Thursday. A tornado threat could materialize as the system moves
inland, depending upon its overall strength.

...Saturday/Day 7 and Sunday/Day 8...
A shortwave trough is forecast to move eastward across the
north-central U.S. on Saturday, as an upper-level low moves across
the Ohio Valley and into the Great Lakes from Saturday into Sunday.
Although the potential for severe storms over the weekend appears to
be low at this time, substantial uncertainty exists at this extended
range.

..Broyles.. 09/08/2024

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ACUS48 KWNS 090852
SWOD48
SPC AC 090851

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0351 AM CDT Mon Sep 09 2024

Valid 121200Z - 171200Z

...DISCUSSION...
...Thursday/Day 4 to Saturday/Day 6...
A tropical cyclone is forecast to move slowly northward through the
lower to mid Mississippi Valley from Thursday to Saturday. A tornado
threat will be possible to the east of the center across much of the
central Gulf Coast region on Thursday. Model forecasts suggest that
the tornado threat could shift northward into the Tennessee Valley
on Friday. On Saturday, uncertainty is considerable concerning the
location of any tropical cyclone remnants. If current solutions are
reasonably close, then a tornado threat would be possible in the
Southeast, potentially from the southern Appalachians into the
Carolinas.

...Sunday/Day 7 and Monday/Day 8...
Mid-level flow is forecast to be relatively weak across the central
and eastern U.S. on Sunday and Monday. The diffuse pattern and weak
deep-layer shear across most of the U.S. suggests that the severe
potential will remain low.

..Broyles.. 09/09/2024

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ACUS48 KWNS 100836
SWOD48
SPC AC 100834

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0334 AM CDT Tue Sep 10 2024

Valid 131200Z - 181200Z

...DISCUSSION...
Severe potential appears low through the period. Primary concern for
D4/Friday is any lingering tornado threat associated with the
remnants of TC Francine. It is forecast by NHC to drift into the
Mid-South/MS Valley to Lower OH Valley vicinity. Latest guidance
indicates further weakening of low-level wind fields on Friday,
likely becoming inadequate to sustain a synoptically evident TC
tornado threat.

Beyond this time frame, a quiescent pattern for severe is expected
this weekend into early next week. Towards mid-week, majority of
ensemble guidance suggests potential large-scale amplification of an
upper trough into the West. This may yield an increase of
low-probability severe around D8 and beyond over parts of the Great
Plains, where many preceding days of above-normal temps will occur.

..Grams.. 09/10/2024

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ACUS48 KWNS 110845
SWOD48
SPC AC 110844

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0344 AM CDT Wed Sep 11 2024

Valid 141200Z - 191200Z

...DISCUSSION...
Severe potential appears low during much of the period, with an area
of interest on D7/Tuesday in the northern Great Plains vicinity.
Guidance consensus suggests a large-scale trough should approach the
West Coast by about D5/Sunday. An embedded shortwave impulse is
generally projected to move northeast across the central Rockies
into the northern High Plains early next week. This may yield at
least a low-probability severe threat, seemingly centered on
D7/Tuesday, in parts of the Dakotas to eastern MT. Typical spread
for this time frame and only modest run-to-run continuity suggest predictability is too low for a 15 percent severe area.

..Grams.. 09/11/2024

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ACUS48 KWNS 120830
SWOD48
SPC AC 120829

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0329 AM CDT Thu Sep 12 2024

Valid 151200Z - 201200Z

...DISCUSSION...
Severe potential appears low during much of the period, but a
low-probability threat may evolve around D6/Tuesday in the
northern/central High/Great Plains vicinity. With weak flow and a
blocking pattern in the East, a large-scale trough should reach the
West Coast by D4/Sunday. Guidance consensus continues to indicate an
embedded shortwave trough ejecting east-northeast over parts of the
West, before pivoting more north-northeastward towards mid-week.
However, run-to-run oscillation persists with both its spatial
evolution and amplitude of an attendant mid-level jet. Today's 00Z
runs suggest a more marginal setup for a 15 percent highlight.

..Grams.. 09/12/2024

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ACUS48 KWNS 130843
SWOD48
SPC AC 130841

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0341 AM CDT Fri Sep 13 2024

Valid 161200Z - 211200Z

...DISCUSSION...
Guidance has trended increasingly consistent with the evolution of a
closed mid/upper low initially over northern/central CA at 12Z
Monday. This low should become an open wave as it pivots northeast
towards the northern High Plains by late Tuesday, likely inducing
surface cyclogenesis in the eastern MT vicinity. Despite increasing
agreement in track/timing, the consensus trend is for a weakening
mid-level jet ejection, in the meridional flow regime ahead of the
trough. As such, the amplitude of the severe-storm risk is still
uncertain, but an area of interest for a future 15 percent highlight
remains evident across the northern High Plains.

This shortwave trough should dampen and slow as it encroaches on the
persistent blocking pattern in the East. In the wake of this wave,
the next in a series of shortwave impulses should amplify along the
Pacific Coast mid-week. Thereafter, predictability drops
considerably by late week.

..Grams.. 09/13/2024

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ACUS48 KWNS 140844
SWOD48
SPC AC 140842

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0342 AM CDT Sat Sep 14 2024

Valid 171200Z - 221200Z

...DISCUSSION...
...D4...
Severe potential may be maximized on D4/Tuesday, but persistent
predictability concerns preclude a 15 percent highlight.

A mid-level low centered the ID/NV/UT border area at 12Z Tuesday
should advance north-northeast towards the MT/AB/SK border area by
12Z Wednesday. Guidance has improved consistency with this track.
But models remain inconsistent with the amplitude of the meridional
mid-level jet to the east of the low, and spatial/temporal spread
appears to have increased with evolution of surface cyclogenesis
over the northern High Plains. It is plausible that a meso-alpha
scale corridor of 15 percent severe probabilities may be warranted
in later outlooks, somewhere in the eastern MT/WY to western Dakotas
vicinity.

The large spread in guidance with the development of a near-coastal subtropical/tropical cyclone on D3 renders minimal predictability
for D4 severe potential in NC and the Lower Mid-Atlantic region.

...D6-8...
Latest guidance has trended towards a slower, positive-tilt
large-scale trough evolution over the West, as the next upstream
shortwave impulse digs back into the Southwest. A moderate mid-level southwesterly flow regime and persistent moderate to well-above
normal temperatures may yield daily bouts of low-probability severe
from the south-central High Plains to the Upper Midwest. Despite
typical predictability concerns in this time frame, overall setup
appears unlikely to support a synoptically evident severe episode.

..Grams.. 09/14/2024

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ACUS48 KWNS 150835
SWOD48
SPC AC 150834

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0334 AM CDT Sun Sep 15 2024

Valid 181200Z - 231200Z

...DISCUSSION...
A shortwave trough near the northern High Plains at 12Z Wednesday
should slow as it largely progresses across the southern Prairie
Provinces. A belt of enhanced mid-level southwesterlies should
linger over the northern Great Plains through Thursday, and aid in a
recharging and downstream advection of steep mid-level lapse rates
over the Dakotas and NE. The low-level moisture plume near the edge
of the EML should be confined, as dry conditions persist in the
Great Lakes region, on the backside of the low-amplitude mid-level
trough over the East. Low-probability severe may occur along a
portion of a weak cold front on Thursday in the north-central
states.

The next shortwave trough that amplifies into the Southwest should
remain positive tilt and slow moving, until around next weekend when
guidance consensus suggests it accelerates northeastward as another
shortwave trough digs into the Northwest. This pattern should yield
more muted mid-level lapse rates over most of the Great Plains,
especially into next weekend. As such, severe probabilities may
remain low through the period.

..Grams.. 09/15/2024

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ACUS48 KWNS 160854
SWOD48
SPC AC 160853

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0353 AM CDT Mon Sep 16 2024

Valid 191200Z - 241200Z

...DISCUSSION...
...D4/Upper Midwest...
Lower-end severe potential remains evident on Thursday afternoon to
evening across a focused portion of the Upper Midwest, centered on
the eastern Dakotas to western MN per latest guidance. A shortwave
trough over the southern Prairie Provinces into the northern Great
Plains should gradually move east. An attendant north/south-oriented
cold front should similarly progress across the Dakotas towards
western MN. In the mid-levels, a plume of steep lapse rates should
be coincident with a belt of enhanced west-southwesterly flow. The
warm-moist sector ahead of the front will likely be confined with
decreasing boundary-layer moisture along/east of the Upper MS
Valley. As such, the overall threat area will probably be fairly
narrow and predictability is too low for a 15 percent highlight.

...D6-7/Southern High Plains to Mid-MO Valley...
The next shortwave trough that amplifies into the Southwest should
remain positive tilt and slow moving, until the weekend when
guidance consensus suggests it accelerates northeastward. The
attendant belt of enhanced mid-level flow around this trough appears
spatially confined, as a ridge dominates from the Lower Rio Grande
Valley to southeast Canada. Coupled with muted mid-level lapse rates
over most of the Great Plains, severe potential appears marginal.

..Grams.. 09/16/2024

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ACUS48 KWNS 170856
SWOD48
SPC AC 170855

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0355 AM CDT Tue Sep 17 2024

Valid 201200Z - 251200Z

...DISCUSSION...
A shortwave trough that amplifies into the Southwest should remain
positive tilt and slow moving into this weekend. Guidance has
trended towards greater consistency with the evolution of its
attendant belt of enhanced mid-level flow ahead of the trough. Based
on current timing, a focused corridor of severe potential may
develop on D5/Saturday afternoon in the southern High Plains. With a
stout mid-level anticyclone anchored over south TX and 500-mb
temperatures warmer than -2 C across roughly the southeast
two-thirds of TX, a potential corridor of 15 percent probabilities
would likely be confined to the mesoscale. Predictability is too low
to confidently highlight such a corridor at this temporal scale.
After D5, predictability on the synoptic scale wanes considerably.
Guidance spread becomes large with the evolution of northern-stream
shortwave troughs and their influence on this southern-stream wave.

..Grams.. 09/17/2024

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ACUS48 KWNS 180856
SWOD48
SPC AC 180854

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0354 AM CDT Wed Sep 18 2024

Valid 211200Z - 261200Z

...DISCUSSION...
Lower-end severe potential should return on D4/Saturday in advance
of a southern-stream shortwave trough over the Southwest. A
mid-level jetlet, with 500-mb winds from 50-60 kts, is progged to
eject across NM as the shortwave trough reaches the Four Corners
area. A mesoscale corridor of severe storms might develop Saturday
afternoon across a part of eastern NM or Far West TX. The expected
buoyancy plume should be modest in amplitude and rather confined
spatially owing to mid-level temperatures warmer than -3 C at 500 mb
across much of TX.

This shortwave trough may weaken slightly as it progresses towards
the central Great Plains on D5/Sunday. But moderate mid-level
southwesterlies may overspread a plume of rich low-level moisture
arcing to the west-northwest from the Mid/Lower MS Valley. A
mesoscale corridor of focused severe potential could develop in
parts of KS/NE to western MO.

Predictability for each scenario on D4-5 remains too low to
confidently delineate a 15 percent area at these spatiotemporal
scales. Larger-scale pattern predictability becomes too low into
early next week.

..Grams.. 09/18/2024

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ACUS48 KWNS 190857
SWOD48
SPC AC 190856

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0356 AM CDT Thu Sep 19 2024

Valid 221200Z - 271200Z

...DISCUSSION...
Some severe potential is evident on both D4/Sunday and D5/Monday.
But both regimes appear to be focused on the mesoscale, rendering
insufficient predictability at this time frame for a 15 percent
highlight. A combination of both low predictability and potential is
apparent mid-week next week.

A southern-stream shortwave trough is expected to progress from the
Southwest into the central Great Plains on D4. A confined belt of
enhanced mid-level southwesterlies overspreading a corridor of rich boundary-layer moisture just ahead of an attendant weak surface
cyclone may yield a severe-storm threat on Sunday afternoon. Per
consensus of latest guidance, the most favored area could be
centered around the Lower MO Valley. This shortwave trough may
continue northeastward towards the Upper MS Valley into D5. Guidance
spread increases with the degree of forward speed, along with
potential weakening of the flow fields surrounding the trough.
Still, a similar setup may occur on Monday in parts of the Midwest,
centered on the southwest Great Lakes region. Mid-level lapse rates
on both days are uniformly depicted to be weak, suggestive of
lower-end severe potential.

..Grams.. 09/19/2024

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ACUS48 KWNS 200733
SWOD48
SPC AC 200731

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0231 AM CDT Fri Sep 20 2024

Valid 231200Z - 281200Z

...DISCUSSION...
Th latest suite of forecast guidance continues to show large spread
during the Day 4-8/Mon-Fri period. While the evolution of a central
U.S. upper trough is uncertain, it seems likely general troughing
across the eastern half of the U.S. will develop. Some severe
potential could develop around Days 4-5/Mon-Tue from the Midwest to
the Mid-Atlantic as a surface cold front advances east into a
seasonally moist airmass amid moderately enhanced mid/upper flow.
Severe potential should decrease late in the forecast period as the
surface trough moves offshore the Atlantic and Gulf coasts and
surface high pressure builds across the Midwest.

..Leitman.. 09/20/2024

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ACUS48 KWNS 210754
SWOD48
SPC AC 210752

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0252 AM CDT Sat Sep 21 2024

Valid 241200Z - 291200Z

...DISCUSSION...
Forecast confidence is low during the Day 4-8 period as large spread
is evident across medium range forecast guidance. Some low-end
severe potential (sub-15 percent) may continue into Day 4/Tuesday
over parts of the OH/TN Valleys and adjacent Appalachians as a
surface cold front continue to progress east amid modest mid/upper
level southwesterly flow. Thereafter, guidance suggests a cut-off
upper low will develop over some part of the central section of the
CONUS, though confidence is the evolution of this feature is low.
Despite this uncertainty, severe potential appears low beyond Day
4/Tuesday given prior cold frontal passage and limited Gulf return
flow.

..Leitman.. 09/21/2024

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ACUS48 KWNS 220836
SWOD48
SPC AC 220835

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0335 AM CDT Sun Sep 22 2024

Valid 251200Z - 301200Z

...DISCUSSION...
Large spread among guidance is apparent during the Day 4-8 period.
Most guidance develops an upper cyclone over the central or eastern
U.S. for much of the period, while an upper ridge persists over the
western states. However, the GFS suite of guidance is much more
progressive with the central/eastern upper trough/low compared to
the ECMWF, and eventually develops a broad upper ridge over much of
the CONUS late in the period. Given vastly different forecast
solutions, confidence in any severe potential developing during the
forecast period is low.

..Leitman.. 09/22/2024

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ACUS48 KWNS 230843
SWOD48
SPC AC 230842

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0342 AM CDT Mon Sep 23 2024

Valid 261200Z - 011200Z

...DISCUSSION...
Some severe potential may develop over parts of the South/Southeast
on Day 4/Thu in relation to the potential tropical cyclone currently
over the western Caribbean. Uncertainty in the evolution/track of
this system precludes severe probabilities at this time. Beyond Day
4/Thu, increasing spread among forecast guidance and a somewhat
anomalous mid/upper level pattern lends to low predictability.
However, while uncertainty exists regarding the overall evolution of
an eastern upper trough/cut-off cyclone, severe potential in general
appears low given potential for widespread rainfall along with poor
lapse rates/instability.

..Leitman.. 09/23/2024

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ACUS48 KWNS 240751
SWOD48
SPC AC 240750

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0250 AM CDT Tue Sep 24 2024

Valid 271200Z - 021200Z

...DISCUSSION...
A low-end tropical cyclone related tornado risk may continue into
Day 4/Fri from parts of the Southeast toward the central Appalachian
vicinity. However, spread among medium range guidance is quite large
at this time frame regarding the position of the remnant tropical
cyclone.

Beyond Day 4/Fri, medium range guidance generally maintains an
closed upper cyclone across the broader Mid-South and Ohio Valley
vicinity through Day 6/Sun before this feature weakens and an open
wave trough evolves and progresses east toward the Atlantic coast
through early next week. Meanwhile, upper ridging will persist
across much of the western half of the CONUS. Overall, severe
potential beyond Day 4/Fri appears low given areas of widespread
precipitation and cloudiness, along with limited instability and
weakening deep-layer flow with time.

..Leitman.. 09/24/2024

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ACUS48 KWNS 250739
SWOD48
SPC AC 250738

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0238 AM CDT Wed Sep 25 2024

Valid 281200Z - 031200Z

...DISCUSSION...
Severe potential is expected to remain low during the Day 4-8
period. The upper cyclone over the Mid-South on Day 4/Sat slowly
weaken an meander east/northeast through Day 5/Sun. General upper
troughing over the eastern third of the CONUS will then be
reinforced by a shortwave trough developing east from the northern
Plains to the Northeast Days 6-8/Mon-Wed. As this shortwave trough
shifts east early next week, a surface cold front will sweep across
the Midwest. However, severe potential associated with this system
will be mitigated by weak instability and poor alignment of stronger
vertical shear. Meanwhile, an upper ridge will persist over the
Great Basin and portions of the Plains, with generally weak
deep-layer flow expected across these areas.

..Leitman.. 09/25/2024

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ACUS48 KWNS 260817
SWOD48
SPC AC 260816

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0316 AM CDT Thu Sep 26 2024

Valid 291200Z - 041200Z

...DISCUSSION...
The upper low over the OH Valley will weaken and become an open wave
early next week. Meanwhile, upper troughing across the east will be
reinforced through midweek by a shortwave trough developing
east/southeast across the Great Lakes. A surface cold front will
develop east/southeast across much of the Plains and Midwest through
Day 6/Tue. However stronger deep-layer flow will remain displaced
well to the north and behind the front. Meanwhile, low-amplitude
upper ridging will prevail across the Southwest/Four Corner, while a
series of shortwave troughs migrate through more progressive
northern stream flow near the international border in the vicinity
of the Pacific Northwest and northern Rockies. Overall severe
thunderstorm potential appears low during the Day 4-8 period.

..Leitman.. 09/26/2024

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ACUS48 KWNS 270816
SWOD48
SPC AC 270815

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0315 AM CDT Fri Sep 27 2024

Valid 301200Z - 051200Z

...DISCUSSION...
Early next week, the upper low in the Tennessee/lower Ohio Valleys
will become an open wave and progress offshore by Wednesday, losing
amplitude with time. Upper-level troughing will shift out of the
northern Plains and into the Great Lakes early to mid next week. A
very weak surface pattern will exist ahead of the initial shortwave
trough in the vicinity of the Carolinas Monday/Tuesday. Though
modest mid-level flow enhancement will remain over the region, these
strong winds will generally be behind the main frontal zone likely
near and just offshore. Further uncertainty is introduced due to
precipitation and cloud cover. Elsewhere, cooler and more stable
conditions will move in behind the second, stronger shortwave
trough. By late next week, upper-level flow is expected to become
more zonal and the strongest flow will be near the Canadian border.
Potential for severe weather continues to appear low through the end
of next week.

..Wendt.. 09/27/2024

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ACUS48 KWNS 280823
SWOD48
SPC AC 280822

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0322 AM CDT Sat Sep 28 2024

Valid 011200Z - 061200Z

...DISCUSSION...
By the middle of next week, upper-level flow across the CONUS is
expected to become more zonal and the jet stream will be generally
located along the Canadian border. The more pronounced troughs in
the northern CONUS will help to push cooler drier air into much of
the country. A modestly moist airmass will be limited to portions of
the Southeast. Broadly stable conditions will limit severe
thunderstorm potential at least through the end of the week. Model
guidance shows some potential for flow aloft to amplify next
weekend. This could encourage moisture return northward. However,
the quality of this moisture as well as the timing of upper-level
troughs is highly uncertain this far in advance.

..Wendt.. 09/28/2024

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ACUS48 KWNS 290841
SWOD48
SPC AC 290839

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0339 AM CDT Sun Sep 29 2024

Valid 021200Z - 071200Z

...DISCUSSION...
Zonal flow aloft is expected to persist into late next week across
the CONUS. The upper-level jet will be displaced northward to near
and along the Canadian border. As successive shortwave troughs move
through that zone of stronger flow, cooler/drier air will move
southward into much of the Plains and parts of the
Midwest/Northeast. By next weekend, there is some potential for some upper-level flow amplification with a ridge developing in the West
and shortwave troughs moving into the eastern third of the CONUS.
However, models remain rather divergent in their exact depiction of
this evolution (the ECMWF deterministic/ensemble is more amplified
than its GFS counterparts). Further increasing uncertainty, the
degree of moisture return ahead of any potential shortwave trough is questionable given the expected frontal progression to along/near
the Gulf Coast.

..Wendt.. 09/29/2024

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ACUS48 KWNS 300840
SWOD48
SPC AC 300839

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0339 AM CDT Mon Sep 30 2024

Valid 031200Z - 081200Z

...DISCUSSION...
Potential for severe weather continues to appear limited on Thursday
and Friday as upper-level flow will remain primarily zonal across
the CONUS along with a surface pattern that will not promote
northward advection of moisture. By the weekend, the predictability
of the upper-level pattern begins to decrease quickly. Both the GFS
and ECMWF show flow trying to amplify in the northern half of the
CONUS. However, the wave pattern between the two models is out of
phase. The ECMWF would suggest at least some low potential for
severe weather, given a greater southward advancement of an upper
trough this weekend into early next week. Even if this evolution is
to verify, this severe potential would be conditional on the
magnitude and quality of moisture return after another front moves
into the Gulf Coast region late next week.

..Wendt.. 09/30/2024

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ACUS48 KWNS 010821
SWOD48
SPC AC 010819

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0319 AM CDT Tue Oct 01 2024

Valid 041200Z - 091200Z

...DISCUSSION...
Recent model guidance has come into better agreement with regard to
the upper-level pattern this weekend into early next week. As zonal
flow begins to break down this Friday, an upper-level trough will
dig southeastward and strengthen. Though conditional and uncertain,
some severe threat could develop in association with this trough.
After this trough exits the East Coast, ridging aloft and at the
surface is expected to develop in its wake.

On Saturday, a cold front will move through the Upper Midwest. Some
moisture return is possible on the western flank of the surface
ridge, but the quality of this moisture is highly uncertain. Wind
fields would support organized storms in parts of the upper
Mississippi Valley, but predictability remains quite low.

For Sunday, the upper-level trough will continue southeastward with
some intensification expected, especially towards Monday morning. A
similar setup to Saturday will occur in parts of the upper Ohio
Valley region. The strongest shear will likely be post-frontal, but
some stronger storms could develop along the front during the
afternoon. Moisture return ahead of the boundary remains a question
and will be the key to severe potential.

A strong mid-level jet will dig into the Mid-Atlantic Monday
morning. Given the misaligned timing of the trough with diurnal
heating, it is not clear that sufficient buoyancy will be present
for an organized severe threat.

..Wendt.. 10/01/2024

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ACUS48 KWNS 020833
SWOD48
SPC AC 020832

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0332 AM CDT Wed Oct 02 2024

Valid 051200Z - 101200Z

...DISCUSSION...
A strong upper trough will move through the Northern Plains and into
the upper Great Lakes region on Saturday. An attendant cold front
will move eastward along with the trough. This system will then move
into the lower Great Lakes/Ohio Valley on Sunday before digging
southeastward into the Mid-Atlantic on Monday. Thereafter, models
forecast upper ridging to build in across much of the CONUS by the
middle of next week, broadly reducing severe weather potential in
the process.

...Upper Mississippi Valley...
Forcing from the upper-level trough will be strong on Saturday.
Storms could develop along the cold front and wind shear would be
sufficient for organized storms. Uncertainty remains rather high as
the quality of moisture return along the western flank of the
anticyclone to the east will be key to overall magnitude of severe
potential, should any materialize.

...Upper Ohio Valley...
As the upper trough and cold front continue eastward, some
destabilization could occur ahead of the front on Sunday afternoon.
As with Saturday, moisture quality ahead of the front remains a
major question. Severe potential remains uncertain.

..Wendt.. 10/02/2024

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ACUS48 KWNS 030841
SWOD48
SPC AC 030839

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0339 AM CDT Thu Oct 03 2024

Valid 061200Z - 111200Z

...DISCUSSION...
A strong upper trough will broaden across the Upper Midwest into
parts of the Northeast on Sunday. An associated cold front will move
through the upper Ohio Valley on Sunday and off the Mid-Atlantic
Coast early to mid morning on Monday. Thereafter, broad troughing
will remain in the Northeast until late in the week as an expansive
upper ridge envelops much of the CONUS.

...Upper-Ohio Valley Vicinity...
The cold front will continue eastward on Sunday, moving through Ohio
during the mid/late afternoon. Moisture return ahead of the front
will be the main source of uncertainty in terms of how much severe
threat there could be. Mid-level forcing will be sufficient, but
low-level veering ahead of the front suggests uncertain storm
coverage. A conditional threat for damaging winds exists during the
late afternoon.

..Wendt.. 10/03/2024

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ACUS48 KWNS 040836
SWOD48
SPC AC 040834

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0334 AM CDT Fri Oct 04 2024

Valid 071200Z - 121200Z

...DISCUSSION...
Medium-range guidance continues to show cyclonic flow aloft
persisting over the northeast CONUS from D4/Monday into D6/Wednesday
before extensive upper ridging over the western and central CONUS
builds eastward and displaces the cyclone. Even with this cyclonic
flow persisting early next week, much of the low-level moisture will
likely be off the Northeast coast by early D4/Monday. Modest
low-level moisture will likely linger across much of the Southeast
and Gulf Coast for much of the week, with some thunderstorm threat
persisting, predominately across the FL Peninsula.

Dry and stable conditions are currently expected elsewhere across
the CONUS as upper ridging builds eastward and the continental
airmass remains in place.

..Mosier.. 10/04/2024

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ACUS48 KWNS 050845
SWOD48
SPC AC 050843

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0343 AM CDT Sat Oct 05 2024

Valid 081200Z - 131200Z

...DISCUSSION...
A mature mid-latitude cyclone is forecast to gradually shift
eastward across southern Quebec on D4/Tuesday and D5/Wednesday as a
series of shortwave troughs rotate through the enhanced mid-level
flow throughout its base. At the same time, expansive upper ridging
will build eastward. By early D6/Thursday, this ridging is expected
to extend from the Southwest northward across the Plains and Upper
MS Valley into Ontario. Further eastward progression/expansion of
this ridging is anticipated on D7/Friday, although some dampening is
possible along its northern periphery over the Canadian Prairies.
This pattern evolution will maintain a stable airmass across the
majority of the CONUS.

The only exception is across FL, where a tropical airmass will
remain in place throughout the period. Additionally, medium-range
guidance continues to suggest tropical cyclone development could
occur over the Gulf of Mexico, with potential impacts across the FL
Peninsula on D4/Tuesday and D5/Wednesday.

..Mosier.. 10/05/2024

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ACUS48 KWNS 060835
SWOD48
SPC AC 060833

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0333 AM CDT Sun Oct 06 2024

Valid 091200Z - 141200Z

...DISCUSSION...
The National Hurricane Center is forecasting Tropical Cyclone Milton
to move across the Florida Peninsula on Wednesday/Day 4. A tornado
threat, associated with Milton, will likely affect parts of the
Florida Peninsula throughout much of the day, and possibly into the
night period. The magnitude of Milton as it crosses the Florida
Peninsula, and any associated severe threat, is highly uncertain at
this time. It seems probable that Milton will be in the western
Atlantic by Thursday morning, which would push the tornado threat
away from the Florida Peninsula. From Friday to Sunday, a
quasi-stationary front is forecast to remain in the vicinity of the
Gulf Coast, with the moist airmass to the south of the front
forecast to remain mostly offshore across the Gulf of Mexico.
Although some thunderstorms could occur over parts of the Florida
Peninsula from Thursday to Sunday, instability is forecast to be too
week for a severe threat.

..Broyles.. 10/06/2024

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ACUS48 KWNS 070832
SWOD48
SPC AC 070830

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0330 AM CDT Mon Oct 07 2024

Valid 101200Z - 151200Z

...DISCUSSION...
Current forecast track from the National Hurricane Center places
Hurricane Milton just off the east-central FL Coast early
D4/Thursday morning. This system is expected to interact with a
larger scale upper trough moving across the eastern CONUS throughout
the day on D4/Thursday, causing it to eject quickly northeastward
into the Atlantic. Upper ridging will likely be in place from the
Southwest into the Upper Great Lakes on D4/Thursday, and this
ridging is expected to shift eastward in the wake of the eastern
CONUS troughing. Some dampening of this ridge is possible on
D4/Thursday and D5/Friday as a shortwave trough progresses
throughout its northern periphery across central Canada and
Ontario/Upper Great Lakes. The northern stream is expected to stay
fairly active during the weekend, with another shortwave trough
likely dropping from the Canadian Prairies and Great Lakes on
D7/Sunday.

Any stronger mid-level flow will be displaced north of the better
low-level moisture on D4/Thursday and D5/Friday. Some moisture
return into the Mid MS and OH Valleys is possible on D6/Saturday and
D7/Sunday, ahead of a potential cold front that is currently
expected to move through on D7/Sunday. Current guidance suggest the
moisture return will be limited, tempering the overall buoyancy and
keeping the severe potential low.

..Mosier.. 10/07/2024

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ACUS48 KWNS 080818
SWOD48
SPC AC 080816

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0316 AM CDT Tue Oct 08 2024

Valid 111200Z - 161200Z

...DISCUSSION...
A pair of fast-moving, low-amplitude shortwave troughs are expected
to progress through the enhanced westerly flow over southern Canada
throughout the period. The first shortwave is forecast to move from
Ontario through the St. Lawrence Valley and New England on
D4/Friday. The second shortwave will follow quickly in the wake of
the first, progressing from the Canadian Prairies through the Upper
Midwest and Upper Great Lakes on D5/Saturday. Beginning late
D5/Saturday or early D6/Sunday, this second shortwave may further
mature into a cyclone over eastern Ontario. This cyclone is then
forecast to drift eastward early next week, with upper troughing
associated with this system expanding over the central and eastern
CONUS.

Some modest moisture return is possible into the Mid MS and OH
Valleys on D5/Saturday and D6/Sunday, ahead of a potential cold
front that is currently expected to move through on D6/Sunday.
Current guidance suggest the moisture return, and associated
buoyancy, will be limited, tempering the overall buoyancy and
keeping the severe potential low. A dry continental airmass will
build in behind the front, promoting stable conditions the majority
of the central and eastern CONUS early next week.

..Mosier.. 10/08/2024

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ACUS48 KWNS 090832
SWOD48
SPC AC 090830

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0330 AM CDT Wed Oct 09 2024

Valid 121200Z - 171200Z

...DISCUSSION...
Overall upper pattern across the central and eastern CONUS is
expected to undergo significant amplification from D4/Saturday into
D7/Tuesday as a series of shortwave troughs move through
progressively deeper troughing. By early D7/Tuesday, upper troughing
is expected to extend from the primary cyclone over the Canadian
Maritimes into the central Plains.

A cold front is expected to accompany the first shortwave trough,
moving across the eastern CONUS on D4/Saturday and D5/Sunday.
Limited buoyancy should keep the thunderstorm potential along this
front low. Strong ridging will follow in the wake of this front,
with dry and stable conditions precluding thunderstorms across the
majority of the CONUS. The only exception is along the Gulf
Coast/Florida, where enough low-level moisture may be in place to
support some thunderstorms.

..Mosier.. 10/09/2024

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ACUS48 KWNS 100832
SWOD48
SPC AC 100831

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0331 AM CDT Thu Oct 10 2024

Valid 131200Z - 181200Z

...DISCUSSION...
Upper troughing is expected to deepen across the central and eastern
CONUS from D4/Sunday through at least D6/Tuesday. At the same time,
ridging will build across the western CONUS. This overall pattern
will likely shift eastward by D7/Wednesday as another upper trough
approaches the West Coast. As a result, an amplified
trough/ridge/trough pattern will likely extend across the CONUS by
early D7/Wednesday.

Stable conditions are expected to prevail across the majority of the
CONUS from D5/Monday through D8/Thursday. A few thunderstorms do
appear possible from the middle to upper OH Valley into Upstate NY
and central PA on D4/Sunday as a shortwave trough and associated
surface low/cold front move through the region. Strong large-scale
ascent is anticipated ahead of the shortwave, with robust mid-level
flow moving across the region as well. However, the better low-level
moisture and associated buoyancy will be displaced south, likely
keeping the overall severe threat low.

..Mosier.. 10/10/2024

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ACUS48 KWNS 110842
SWOD48
SPC AC 110840

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0340 AM CDT Fri Oct 11 2024

Valid 141200Z - 191200Z

...DISCUSSION...
Medium-range guidance indicates that there will be substantive
further amplification of large-scale mid-level troughing to the east
of the Mississippi Valley early next week. Peak amplitude may occur
near/east of the Atlantic Seaboard early Wednesday, when cool
surface ridging may encompass much of the interior U.S. into areas
offshore of the Gulf and southern Atlantic coasts.

Although another vigorous digging short wave impulse may reinforce
the larger-scale mid-level troughing near the northern Atlantic
Seaboard into late week, a southerly return flow may develop across
the southern Great Plains toward the Upper Midwest, ahead of
significant mid-level troughing emerging from the mid-latitude
Pacific. It is possible that this could be accompanied by at least
some increase in thunderstorm development ahead of an associated
cold front Thursday through Friday. However, it is not yet clear
that low-level moistening will contribute to sufficient
destabilization to support more than low probabilities for severe thunderstorms.

..Kerr.. 10/11/2024

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ACUS48 KWNS 120850
SWOD48
SPC AC 120849

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0349 AM CDT Sat Oct 12 2024

Valid 151200Z - 201200Z

...DISCUSSION...
It still appears that an evolving large-scale eastern U.S. upper
trough will reach peak amplitude near the Atlantic Seaboard around
the middle of next week, when cool surface ridging may encompass
much of the interior U.S. into areas offshore of the Gulf and south
Atlantic coasts. Thereafter, even as the mid-level troughing
progresses into the Atlantic and loses amplitude, medium-range
guidance indicates that surface ridging will be maintained across
the northwestern Gulf coast vicinity, on the southwestern flank of a
retreating surface high.

There appears greater spread within the model output concerning
possible subsequent significant surface cyclogenesis from the lee of
the Canadian/northern U.S. Rockies through the interior higher
latitudes of Canada, in response to forcing associated with a short
wave trough emerging from the mid-latitude Pacific during the middle
to latter portion of next week. Even though this may initially
include the development of fairly deep surface troughing from the
lee of the northern U.S. Rockies into the Great Plains, it appears
that low-level Gulf moisture return will be limited. While there
may be some increase in thunderstorm activity across parts of the
Great Plains by next Thursday and Friday, the lack of widespread
appreciable destabilization will probably tend to minimize the risk
for severe thunderstorms.

..Kerr.. 10/12/2024

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ACUS48 KWNS 130847
SWOD48
SPC AC 130845

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0345 AM CDT Sun Oct 13 2024

Valid 161200Z - 211200Z

...DISCUSSION...
Initially amplified mid-level troughing near the Atlantic Seaboard
is forecast to shift offshore and lose amplitude across the western
Atlantic during the middle to latter portion of the coming work
week. In its wake, medium-range guidance indicates at least a
couple of significant short wave perturbations will emerge from a
somewhat more progressive regime across the mid-latitude latitude
Pacific.

It still appears that the lead perturbation may provide support for
strong surface cyclogenesis to the lee of the Canadian and northern
U.S. Rockies during the latter portion of this week. While there is
variance among the models concerning early evolution south of the
international border, primary cyclone development is appearing most
probable across the Canadian Prairies into higher latitudes of
interior Canada. As this occurs, a trailing cold front may overtake
modestly deep surface troughing across the northern into central
U.S. Great Plains Thursday into Friday. This could become a focus
for a corridor of increasing thunderstorm development. However, it
still appears that rather modest to weak low-level moisture return,
in the wake of a prior cool/dry intrusion as far south as the
northern Gulf of Mexico, will tend to limit destabilization and
minimize the risk for severe storms.

Models indicate that the second impulse, quickly progressing inland
behind the lead wave, will tend to split off toward the southern
mid-latitudes. However, the differences between the ECENS/ECMWF and
GEFS/GFS remain quite large concerning the amplification and
progressiveness of this perturbation across the central/southern
U.S. late this week into next weekend. Even so, with low-level
moisture return off the Gulf of Mexico initially limited, and then
perhaps impeded by the progression of the lead system, it is not
clear whether these differences will have much impact on the overall
convective potential.

..Kerr.. 10/13/2024

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ACUS48 KWNS 140840
SWOD48
SPC AC 140838

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0338 AM CDT Mon Oct 14 2024

Valid 171200Z - 221200Z

...DISCUSSION...
There appears much better consensus between the ECENS/ECMWF and
GEFS/GFS concerning the evolution of the mid/upper flow late this
week into early next week. Within larger-scale mid-level troughing
developing inland of the Pacific coast by mid week, one embedded
short wave impulse progressing northeast of the Canadian Rockies at
the outset of the period is forecast to pivot across the Canadian
Prairies into the higher latitudes of interior Canada, accompanied
by the consolidating primary surface cyclone.

It now appears probable that the significant trailing short wave
perturbation will undergo considerable amplification and split off
the main belt of westerlies, while digging inland of the northern
Pacific coast. It appears that this will include the evolution of a
deepening mid-level low near/east of the Sierra Nevada into the
Southwest, where it may linger into next weekend as low-amplitude
ridging shifts inland within the westerlies across the Canadian Rockies/Prairies and adjacent international border vicinity. As
westerly mean flow then strengthens downstream of digging
large-scale troughing off the Pacific coast late this weekend into
early next week, it appears that the low will transition to an open
wave and accelerate across the Rockies through the central Great
Plains, around the northern periphery of building ridging in the
subtropical latitudes.

Preceding the emergence of the perturbation from the Southwest, the
models continue to indicate that the development of a moistening
southerly return flow off the Gulf of Mexico will be impeded by the
maintenance of surface ridging across much of the eastern U.S.
through northwestern Gulf coast vicinity. While some strong
thunderstorm development might not be entirely out of the question, particularly Friday with some modest initial moistening near
lingering relatively deep surface troughing across the central high
plains, the risk for severe weather appears generally low through
this period.

..Kerr.. 10/14/2024

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ACUS48 KWNS 150847
SWOD48
SPC AC 150846

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0346 AM CDT Tue Oct 15 2024

Valid 181200Z - 231200Z

...DISCUSSION...
Medium-range guidance indicates that a closed low will form within
an amplifying short wave trough digging southeast of the southern
Great Basin/lower Colorado Valley by early Friday. It appears
probable that this will become cut off from the westerlies, with the
center of the modestly broad circulation lingering near or southwest
of the Four Corners into early Sunday, as low-amplitude ridging
passes by to the north, near the western through central
Canadian/U.S. border area. Sunday into Monday, models suggest that
it may come under the influence of strengthening westerly mean flow, transitioning to an open wave and accelerating northeastward into
the central Great Plains, before continuing to migrate around the
northeastern periphery of building mid-level ridging centered over
the subtropics.

Models continue to indicate that this is unlikely to become
accompanied by significant surface cyclogenesis to the lee of the
southern Rockies. And low-level moisture return in the wake of
weakening cold surface ridging across the northwest Gulf Coast
region may remain modest to weak. While modestly steep lapse rates
may contribute to isolated to widely scattered strong diurnal
thunderstorm development near surface troughing to the lee of the
Front Range, Sangre de Cristo and Sacramento Mountains Friday
through Sunday, the overall severe weather potential still appears
generally low.

..Kerr.. 10/15/2024

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ACUS48 KWNS 160824
SWOD48
SPC AC 160822

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0322 AM CDT Wed Oct 16 2024

Valid 191200Z - 241200Z

...DISCUSSION...
Latest medium-range guidance is not much different that prior runs
for this period. A fairly significant lower/mid-tropospheric
cyclone may remain centered near the Four Corners, cut off from the
westerlies, before beginning to slowly accelerate eastward on
Sunday. As the southern/southwestern flank of cool surface ridging
is generally maintained across the northern Gulf of Mexico into
northwestern Gulf coast vicinity, and impedes low-level moistening
across the southern Great Plains, the potential for severe
thunderstorm development appears likely to remain rather limited.

As the remnant perturbation progresses more rapidly east of the
southern Rockies through the interior U.S., around the northeastern
periphery of building mid-level ridging centered over the
subtropics, models continue to indicate little in the way of
appreciable surface cyclogenesis and moistening southerly return
flow. As a result, the potential for severe thunderstorm
development is expected to remain generally low through the early to
middle portion of next week.

..Kerr.. 10/16/2024

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ACUS48 KWNS 170838
SWOD48
SPC AC 170837

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0337 AM CDT Thu Oct 17 2024

Valid 201200Z - 251200Z

...DISCUSSION...
An initially evolving mid-level low is still forecast to emerge from
the Four Corners vicinity late this weekend, before accelerating
east of the southern Rockies and across the remainder of the
interior U.S., generally around the northern/northeastern periphery
of ridging centered over the subtropics. As this occurs, models
indicate similar pattern developments upstream, but over the
southern mid-latitude Pacific, with another notable mid-level low
evolving to the northwest of 30N/140W early next week, before
accelerating toward the U.S. Pacific coast by the end of the period.

While there appears at least some risk for a couple of strong storms
across the Texas/Oklahoma Panhandle vicinity into the lower central
Great Plains Sunday into Monday, the lack of a substantive return
flow of moisture from the Gulf of Mexico is still expected to
minimize the overall convective potential. Models indicate that
weak surface ridging may linger across the Gulf Coast vicinity
through much of the period, impeding the development of a moistening
southerly inland return flow and maintaining generally low risk for
severe thunderstorm activity.

..Kerr.. 10/17/2024

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ACUS48 KWNS 180834
SWOD48
SPC AC 180833

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0333 AM CDT Fri Oct 18 2024

Valid 211200Z - 261200Z

...DISCUSSION...
For this coming Monday, a shortwave trough is forecast to move into
the central Plains. Models indicate that a narrow, and increasingly
limited, band of moisture will be present ahead of the trough and
associated surface front. Though thunderstorms are possible in parts
of eastern Kansas with this activity, severe weather potential
appears low at this time.

As the central Plains trough moves east, it is expected to lose
amplitude and eventually phase with a stronger, broader upper trough
moving through the Upper Midwest and Ohio Valley region around the
middle of next week. While models begin to diverge on the
upper-level pattern at that time, the general consensus is for a
cold font to push into parts of the southern Plains as well as to
near the Gulf Coast and off the Atlantic Coast. With moisture ahead
of the front still looking limited, severe thunderstorms do not
appear probable along the boundary. Thereafter, surface ridging in
the eastern third of the CONUS, along with another upper ridge over
the Divide, will keep severe weather potential low through at least
the end of next week and possibly into next weekend.

..Wendt.. 10/18/2024

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ACUS48 KWNS 190849
SWOD48
SPC AC 190848

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0348 AM CDT Sat Oct 19 2024

Valid 221200Z - 271200Z

...DISCUSSION...
A shortwave trough is expected to move into the Midwest before
phasing with a broader upper-level trough in the Great Lakes region
by the middle of next week. Access to Gulf moisture will become more
restricted as this feature moves eastward. Across parts of the West
and Plains, an upper-level ridge will develop and shift east through
the remainder of the week into the weekend. The upper-level pattern
becomes less certain during the weekend, but at least a brief period
of quasi-zonal flow aloft is currently expected. With another
cold-frontal intrusion into the Gulf expected to occur late this
week, moisture availability/quality for any shortwave troughs moving
through the westerlies is highly uncertain. Severe weather potential
continues to appear low through next weekend.

..Wendt.. 10/19/2024

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ACUS48 KWNS 200906
SWOD48
SPC AC 200904

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0404 AM CDT Sun Oct 20 2024

Valid 231200Z - 281200Z

...DISCUSSION...
A progressive mid-level pattern will be in place across the CONUS by
the middle of this week and through the weekend. A cold front will
move through the northeast CONUS on Wednesday with occasional
lightning possible. High pressure will build in across the eastern
CONUS in the wake of this cold front. This will result in fair
weather and minimal severe weather concerns at the end of this week.
Weak lee troughing will resume late Friday and into Saturday across
the central CONUS. Some showers and thunderstorms are possible along
a cold front that will develop and move south. However, moisture
will be quite minimal and thus, the severe weather threat will be
low.

..Bentley.. 10/20/2024

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ACUS48 KWNS 211302
SWOD48
SPC AC 211300

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0800 AM CDT Mon Oct 21 2024

Valid 241200Z - 291200Z

...DISCUSSION...
A mid-level trough will cross the central and eastern CONUS on
D4/Thursday and D5/Friday with a surface front advancing east
through the period. Moisture will remain limited ahead of this front
and thus, severe weather is not expected. In the wake of this front,
high pressure will build into the Midwest on D6/Saturday and move
into the Mid-Atlantic by D7/Sunday. This will result in tranquil
weather through the weekend. Extended range guidance does suggest
the potential for some return moisture flow by early next week, but
there is considerable uncertainty in the upper-level pattern and any
potential severe weather threat would likely be after Monday/D8.

..Bentley.. 10/21/2024

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ACUS48 KWNS 220843
SWOD48
SPC AC 220842

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0342 AM CDT Tue Oct 22 2024

Valid 251200Z - 301200Z

...DISCUSSION...
Severe weather concerns will be minimal D4/Friday to D7/Monday as a
mid-level trough amplifies across the Northeast and a strong surface
high pressure center moves across the eastern CONUS in its wake. By
late in the weekend to early next week, lee troughing will return to
the Plains as a trough traverses the western CONUS. There is still
considerable uncertainty regarding the timing and evolution of this
trough, but in general, there is a consistent signal for a strong
trough to eject out of the western CONUS in the early to middle part
of next week.

Dry air has infiltrated the northern Gulf of Mexico this week with
consistent east-northeasterly flow reinforcing this more continental
airmass through the weekend. Richer low-level moisture is not
forecast to return to the entire Gulf Basin until Tuesday/D8. This
may result in limited inland moisture and instability Monday/D7 and
Tuesday D8, particularly if the trough follows some of the more
progressive guidance. However, if return flow continues for a longer
period before the primary trough ejects, a greater severe weather
threat is possible, but it would likely be beyond Tuesday/D8.

..Bentley.. 10/22/2024

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ACUS48 KWNS 230859
SWOD48
SPC AC 230857

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0357 AM CDT Wed Oct 23 2024

Valid 261200Z - 311200Z

...DISCUSSION...
Severe weather concerns will be minimal D4/Saturday to D6/Monday as
a mid-level trough amplifies across the Northeast and a strong
surface high pressure center moves across the eastern CONUS in its
wake. By late in the weekend to early next week, lee troughing will
return to the Plains as a trough traverses the western CONUS. There
is still considerable uncertainty regarding the timing and evolution
of this trough, but in general, there is a consistent signal for a
strong trough to eject out of the western CONUS in the early to
middle part of next week.

Dry air has infiltrated the northern Gulf of Mexico this week with
consistent east-northeasterly flow reinforcing this more continental
airmass through the weekend. Richer low-level moisture is not
forecast to return to the entire Gulf Basin until Tuesday/D7.
Limited moisture may surge northward on Tuesday/D7 and Wednesday/D8
with some thunderstorms possible. However, there is no clear signal
for severe weather at this time.

..Bentley.. 10/23/2024

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ACUS48 KWNS 240849
SWOD48
SPC AC 240847

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0347 AM CDT Thu Oct 24 2024

Valid 271200Z - 011200Z

...DISCUSSION...
High pressure will dominate the surface pattern across the eastern
CONUS on Sunday. Strong lee troughing will begin across the central
CONUS early next week as a large mid-level trough shifts across the
western CONUS. There is consistency among extended range guidance
for a strong ridge to build across the eastern CONUS which will
result in a positively tilted mid-level trough with multiple
embedded shortwave troughs. As these advect through the flow,
several surface lows will move from the Plains to the Upper
Midwest/Great Lakes next week. Initially, surface moisture will be
lacking across the Plains, but by the middle of the week
Day7/Wednesday, the continued southerly flow will result in better
low-level moisture with 60sF dewpoints potentially as far north as
the Midwest with mid 60s dewpoints into the southern Plains. Once
more robust low-level moisture moves inland and interacts with the
sharp surface front/trough, thunderstorms will be possible. Once
this moisture is in place, severe weather will become more possible
from Day7/Wednesday and beyond. At this time it is unclear how the
evolution of these individual shortwave troughs will occur which
will impact severe weather potential.

..Bentley.. 10/24/2024

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ACUS48 KWNS 250702
SWOD48
SPC AC 250700

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0200 AM CDT Fri Oct 25 2024

Valid 281200Z - 021200Z

...DISCUSSION...
A mid/upper trough will progress eastward from the western U.S. to
the Upper Midwest Days 4-7/Mon-Thu. As this occurs, a belt of strong
mid/upper southwesterly flow will overspread portions of the
southern/central Plains to the upper MS Valley on Day 5/Tue, and
much of the Upper Midwest/Great Lakes vicinity on Day 6/Wed. In
response, a series of surface lows will migrate across the central
Plains to the upper Great Lakes on Days 5-6/Tue-Wed. Increasing
southerly low-level flow will transport 50s to possibly low 60s F
dewpoints northward across the central/southern Plains to the
Mid/Upper MS Valley during this time. Thunderstorm potential will
increase on Day 5/Tue in this warm advection regime ahead of the
trough, and into Day 6/Wed as a cold front is forecast to progress
eastward over the central CONUS. Given strong deep-layer
southwesterly flow and increasing boundary-layer moisture to aid in destabilization, some strong to severe thunderstorms are possible.
However, capping may preclude a greater severe risk on Day 5/Tue as
midlevel temperatures are forecast to be fairly warm. By Day 6/Wed,
strong large-scale ascent may be lifting into the Great Lakes/Canada
and out of phase with better low-level moisture and modest
instability. Given uncertainty, will not introduce any 15 percent
delineations at this time, but outlook areas may be needed in
subsequent outlooks for parts of the central Plains to Upper Midwest
vicinity around Days 5-6/Tue-Wed.

Toward the end of the period, another upper shortwave trough may
eject from the western U.S. into the Plains. However, large spread
in timing and position of this feature is resulting in low
predictability from Day 7/Thu and beyond.

..Leitman.. 10/25/2024

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ACUS48 KWNS 260734
SWOD48
SPC AC 260733

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0233 AM CDT Sat Oct 26 2024

Valid 291200Z - 031200Z

...DISCUSSION...
...Tuesday/Day 4 and Wednesday/Day 5...
An upper-level trough and an associated mid-level speed max are
forecast to move across the Desert Southwest on Tuesday. Southwest
mid-level flow is forecast ahead of the system from the southern
High Plains northeastward into the upper Mississippi Valley.
Moisture advection is forecast on Tuesday within a belt of strong
low-level flow across the southern and central Plains. The moist
airmass may reach the mid Missouri Valley by Tuesday evening where
model forecasts develop scattered thunderstorms. A severe threat
will be possible across parts of the mid Missouri Valley as the
airmass moistens in response to large-scale ascent and relatively
strong deep-layer shear. Some model forecasts suggest that
convective development may be delayed until the late evening and
overnight period. The late initiation would probably keep any severe
threat isolated and marginal due the weakness in instability. Will
not add a threat area at this time due to timing uncertainty
concerning convective initiation.

On Wednesday, convective development with greater coverage is
forecast during the day from the southern Plains north-northeastward
into the upper Mississippi Valley. A moist airmass combined with
strong low-level flow and sufficient instability may result in a
severe threat during the afternoon. At this time, the potential for
severe storms appears conditional along much of the corridor from
eastern Oklahoma northeastward into Wisconsin. A severe threat area
could be needed as confidence increases over the next few model runs
concerning the area with the greatest severe potential.

...Thursday/Day 6 to Saturday/Day 8...
From Thursday to Saturday, multiple shortwave troughs are forecast
to move across the northern tier of the United States. A moist
airmass is forecast to remain in place from the southern Plains
eastward into the Gulf Coast states. Isolated to scattered
thunderstorm development will be possible over parts of this airmass
each day. However, instability and large-scale ascent is forecast to
remain relatively weak suggesting that any severe threat that
develops could remain isolated and marginal.

..Broyles.. 10/26/2024

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ACUS48 KWNS 270900
SWOD48
SPC AC 270858

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0358 AM CDT Sun Oct 27 2024

Valid 301200Z - 041200Z

...DISCUSSION...
...Wednesday/Day 4 and Thursday/Day 5...
An upper-level trough is forecast to move eastward into the central
Rockies and northern Plains on Wednesday, as an associated mid-level
jet translates eastward into the mid Missouri Valley. At the
surface, a cold front is forecast to move east-southeastward across
the Upper Midwest and central Plains. Scattered thunderstorm
development is expected along and ahead of the front during the
afternoon. Sufficient instability combined with strong low-level
flow, and lift associated with the upper-level trough will be
favorable for severe storms across parts of the region.

The most favorable area for severe storms appears to be from north
Texas and Oklahoma northeastward into western and northern Missouri.
GFS forecast soundings along this corridor during the late afternoon
suggest that MLCAPE will peak in the 1000 to 1500 J/kg range. 0-6 km
shear is forecast to be between 40 and 50 knots, with 700-500 mb
lapse in the 7 to 7.5 C/km range. If this environement can
materialize, supercell development with large hail and severe wind
gusts could occur. A chance for very large hail will be possible
with the more intense cells. An isolated tornado threat also appears
possible.

On Thursday, the upper-level trough is forecast to move into the
Great Lakes region, as the cold front advances southeastward into
the Ohio Valley and Ark-La-Tex. Isolated strong to severe storms
will be possible along parts of the front where surface temperatures
are able to warm sufficiently. The strongest low to mid-level flow
is forecast over the mid Mississippi and lower Ohio Valley
suggesting that the potential for organized severe convection could
be displaced away from the strongest instability. Even so,
instability is forecast to remain weak which appears to be the main
limiting factor.

...Friday/Day 6 to Sunday/Day 8...
On Friday, an upper-level trough is forecast to move northeastward
into the north-central U.S., as moisture return takes place in
western parts of the southern Plains. It appears that thunderstorm
development will be possible across parts of west Texas within the
northwestern part of a moist airmass. Large-scale ascent is forecast
to remain relative weak suggesting that any severe threat could be
isolated.

On Sunday, southwesterly mid-level flow is forecast over the Great
Plains, as low-level moisture advection continues. Scattered
thunderstorms will be possible within this moist airmass as surface temperatures warm during the day. At this time, forecast instability
and shear appear marginal for severe storms, and any organized
convection should be relatively isolated.

..Broyles.. 10/27/2024

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ACUS48 KWNS 280858
SWOD48
SPC AC 280857

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0357 AM CDT Mon Oct 28 2024

Valid 311200Z - 051200Z

...DISCUSSION...
...Thursday/Day 4 to Saturday/Day 6...
An upper-level trough is forecast to move eastward into the upper
Mississippi Valley on Thursday, and into the Northeast on Friday. At
the surface, a cold front is forecast to advance southeastward into
the Gulf Coast states. Thunderstorm development will be likely near
and ahead of the front Thursday afternoon and evening. Weak
instability and limited large-scale ascent should keep any severe
threat marginal.

From Friday into Saturday, low-level moisture return is expected to
take place further west into the southern Plains. Thunderstorms are
forecast to develop on Friday over parts of eastern New Mexico and
west Texas, with an isolated severe threat possible. On Saturday,
moisture and instability is forecast to increase across the southern
and central Plains, which could result in an expansion of severe
threat coverage. However, the latest models suggest that instability
will be relatively weak in most areas, helping to marginalize the
severe threat.

...Sunday/Day 7 and Monday/Day 8...
On Sunday and Monday, an upper-level system is forecast to move from
near the southern California coast into northwestern Mexico. Ahead
of the system, an anticyclonic and subtle southwesterly mid-level
flow pattern is forecast in the south-central U.S, where a moist
airmass should be located. Isolated to scattered thunderstorms are
expected to develop on both Sunday and Monday afternoons with this
airmass. The strongest instability is forecast to be near the
western edge of the moist airmass, suggesting the greatest severe
potential could be from west Texas extending north-northeastward
into the central Plains. Forecast instability should be relatively
weak, keeping any severe threat marginal.

..Broyles.. 10/28/2024

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ACUS48 KWNS 290852
SWOD48
SPC AC 290851

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0351 AM CDT Tue Oct 29 2024

Valid 011200Z - 061200Z

...DISCUSSION...
...Friday/Day 4 to Sunday/Day 6...
An upper-level trough is forecast to dig south-southeastward into
California on Friday, as southwesterly mid-level flow remains over
the Great Plains. On Saturday, an upper-level low is forecast to
close off over southern California. The southwesterly flow pattern
will be favorable for moisture advection in the southern Plains over
the weekend. Surface dewpoints are forecast to return into the 60s F
across much of the southern Plains, where scattered thunderstorms
are expected to develop both Friday and Saturday. The latest model
forecasts for this period suggest that MLCAPE will peak each
afternoon in the 500 to 1000 J/kg range, with 0-6 km shear remaining
around 30 knots. This, combined with a lack of large-scale ascent,
is expected to keep any severe threat marginal across the region.
Strong wind gusts and hail should be the primary threats.

The upper-level low is forecast to move slowly eastward towards
southwestern Arizona on Sunday, as the exit region of a mid-level
jet overspreads the southern High Plains. Weak destabilization and
moderate deep-layer shear associated with the jet should support an
isolated severe threat across parts of west Texas Sunday afternoon
and evening.

...Monday/Day 7 and Tuesday/Day 8...
On Monday and Tuesday, the mid-level jet is forecast to move across
the southern and central Plains over a weakly unstable airmass.
Thunderstorm development is expected each day from parts of central
and north Texas northward into Kansas. Although a severe threat will
be possible each afternoon, weak instability is expected to keep any
severe potential relatively isolated.

..Broyles.. 10/29/2024

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ACUS48 KWNS 300804
SWOD48
SPC AC 300803

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0303 AM CDT Wed Oct 30 2024

Valid 021200Z - 071200Z

...DISCUSSION...
...Saturday/Day 4 to Monday/Day 6...
An upper-level trough is forecast to move into the Desert Southwest
on Saturday, as southwesterly mid-level flow remains over the
Rockies and Great Plains. A moist airmass will be in place over much
of the southern and central Plains. Along the western edge of the
moist airmass, moderate instability is forecast to develop from
eastern New Mexico into west Texas. Thunderstorms that develop along
and near this instability axis will have a chance to be severe.
Supercells could produce large hail and isolated severe wind gusts.

On Sunday, low-level moisture advection is expected to continue over
much of the Great Plains, as the upper-level trough moves across the
Desert Southwest. Model forecasts are in reasonably good agreement,
with an axis of moderate instability developing Sunday afternoon
from northwest Texas into western and central Oklahoma northward
into Kansas. Moderate deep-layer shear and steep mid-level lapse
rates should support supercell development, with a potential for
isolated large hail and wind damage. The threat should persist into
the evening as scattered severe storms move eastward across the
southern and central Plains.

On Monday, the upper-level trough is forecast to move through the
southern High Plains, as an 80 to 100 knot mid-level jet ejects
northeastward into the southern and central Plains. Thunderstorms
are expected to develop along a corridor of weak instability from
central and north Texas northeastward into the Ozarks. Moderate
deep-layer shear near the instability axis should support a severe
threat during the afternoon and evening, with damaging wind gusts
and isolated large hail as the primary threats. At this time, the
timing of the ejecting mid-level jet, and magnitude of instability
remain too uncertain to issue a threat area.

...Tuesday/Day 7 and Wednesday/Day 8...
The upper-level trough is forecast to move quickly northeastward
into the Great Lakes region on Tuesday, as mid-level flow remains
southwesterly across the lower to mid Mississippi Valley. Isolated
to scattered thunderstorms are expected to form Tuesday afternoon
ahead of a cold front from the lower to mid Mississippi Valley north-northeastward into the lower Ohio Valley. On Wednesday, the
front is forecast to move southeastward into the Ohio and Tennessee
Valleys, suggesting the potential for isolated severe thunderstorms
would be greatest from Kentucky southwestward into western Tennessee
and northern Mississippi. However, spatial and magnitude uncertainty
are substantial at this range.

..Broyles.. 10/30/2024

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ACUS48 KWNS 010900
SWOD48
SPC AC 010859

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0359 AM CDT Fri Nov 01 2024

Valid 041200Z - 091200Z

...DISCUSSION...
Primary severe potential is focused on D4/Monday from parts of the south-central states into the Mid-MS Valley. An emerging squall line
should develop early morning Monday (late D3 into early D4) across
parts of west TX. This should occur ahead of strong forcing for
ascent attendant to a shortwave impulse and mid-level speed max
moving through the basal portion of a Southwest trough. Consensus of
guidance supports a positive-tilt ejection of this wave into the
central states, with multi-day trends of a weaker surface cyclone.
This should yield meridional deep-layer flow predominantly
paralleling the enlarging squall line. This will also support a
largely asymmetrical low-level flow regime, with the core of the
low-level jet rapidly advancing north-northeast from the
south-central states towards the southern Great Lakes. This should
become increasingly separated from the plume of mid 60s surface dew
points that should struggle to advect beyond the Mid-MS Valley.

The degree of instability with northward extent in OK/KS across the
Mid-MS Valley is questionable with abundant preceding convection
ahead of the probable squall line. Primary daytime severe threat may
be confined to parts of the Red River Valley and TX, with a
late-day/nocturnal severe threat extending northeast towards the
Mid-MS Valley. With weak mid-level lapse rates limiting instability
in the open warm-moist sector, along with the aforementioned
synoptic concerns, confidence is low in how widespread and vigorous
severe wind/tornado potential will be.

..Grams.. 11/01/2024

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ACUS48 KWNS 020842
SWOD48
SPC AC 020841

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0341 AM CDT Sat Nov 02 2024

Valid 051200Z - 101200Z

...DISCUSSION...
A benign pattern for appreciable severe appears likely to commence
by D4/Tuesday, although low-probability severe potential may exist
during the period. In the wake of a dampening positive-tilt
mid/upper trough near the Great Lakes on D4, an upstream shortwave
trough digging over the northern Intermountain West should evolve
into a cutoff low across the Southwest mid-week. A cold front
slowing and then stalling along the western Gulf Coast to Lower MS
Valley should be a focus for convection lingering from D3 into D4.
Weakening of both deep-layer winds and forcing for ascent will be
limiting factors to the severe-storm threat.

Modified moisture return will eventually spread back towards the
southern High Plains, in advance of the cutoff low. This suggests
increasing thunder potential on D6/Thursday, along an inverted
surface trough. Even with some ensemble members suggesting ejection
of the cutoff low onto the central/southern Great Plains late in the
period, the overall pattern appears unlikely to support greater than
15-percent severe probabilities.

..Grams.. 11/02/2024

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ACUS48 KWNS 030941
SWOD48
SPC AC 030939

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0339 AM CST Sun Nov 03 2024

Valid 061200Z - 111200Z

...DISCUSSION...
NHC is forecasting a high probability of TC formation in the
Caribbean by D2. Predictability is low along the FL Gulf Coast
vicinity regarding downstream tornado potential during D4-5, with
large spread in guidance at this time frame and beyond.

Meanwhile, modified moisture return will ensue on D4-5 over the
southern High Plains, in advance of a shortwave trough evolving into
a cutoff low across the Southwest. Given an initially inverted
surface trough, severe potential should be limited/mesoscale-focused
on D5/Thursday. With an emerging consensus of ensemble guidance
suggesting acceleration of the upper low onto the Great Plains,
severe potential may increase next weekend with broadening of the
warm-moist sector in the central states. Predictability is far too
low to warrant consideration of greater than 15 percent areas yet.

..Grams.. 11/03/2024

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ACUS48 KWNS 040906
SWOD48
SPC AC 040905

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0305 AM CST Mon Nov 04 2024

Valid 071200Z - 121200Z

...DISCUSSION...
Modified moisture return from the western Gulf will occur across TX
on D4/Thursday in advance of a slow-moving mid/upper trough over
AZ/NM. A surface anticyclone over the central High Plains to Mid-MO
Valley will support ridging southward across the southern High
Plains, with an inverted trough developing to its east. This
suggests convective development will primarily be elevated near and
west of the inverted trough. To its east, a mesoscale corridor of at
least low-probability severe should emerge across a part of west TX
in later outlooks.

Guidance suggests acceleration of the Southwest upper trough should
occur across the southern High Plains to central Great Plains on D5-6/Friday-Saturday. This overall synoptic pattern and related instability/shear combinations appear to be on the lower-end
spectrum for the OK/TX/AR/LA vicinity. But daily bouts of
mesoscale-driven severe risk are plausible. In the wake of this
wave, a lack of dry continental air intruding into the western Gulf
may yield a broader warm-moist sector beyond D8. Both 00Z ensemble
and deterministic guidance depict above-normal consistency with
indications of an amplifying upper trough around the Rockies
vicinity on D9/Tuesday.

Finally, the forecast evolution of PTC 18 into the Gulf later this
week will bear monitoring for a potential TC-tornado threat along
some portion of the coast.

..Grams.. 11/04/2024

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ACUS48 KWNS 050938
SWOD48
SPC AC 050937

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0337 AM CST Tue Nov 05 2024

Valid 081200Z - 131200Z

...DISCUSSION...
...D4-5/Friday-Saturday...
Guidance suggests acceleration of the Southwest upper trough should
occur across the southern High Plains to central Great Plains. After
an initially inverted surface trough on D3/Thursday, surface cyclone development is expected. Overall model trends have been for greater amplification of the trough and attendant surface reflection. But
spatial spread, that is noticeable on Thursday, increases further
into Friday-Saturday. In addition, very large spread persists with
the potential track of TC Rafael in the Gulf. This may render
peripheral impacts on the surrounding low-level moisture plume ahead
of the Great Plains wave. As such, confidence is low for determining
probable mesoscale-focused severe potential on D4-5 across the
south-central states.

...D8/Tuesday...
After a potential quiet period of severe potential on D6-7, guidance
consensus indicates an amplified upper trough should progress into
the West early next week. This may eventually overlap a broadening
warm/moist sector emanating north from the western Gulf and yield a
return to increasing severe potential towards mid-week. Poor
run-to-run continuity and large ensemble spread exists with the
evolution of this trough for now.

..Grams.. 11/05/2024

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ACUS48 KWNS 060938
SWOD48
SPC AC 060937

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0337 AM CST Wed Nov 06 2024

Valid 091200Z - 141200Z

...DISCUSSION...
Modest severe potential remains apparent during parts of the
extended period.

A mid/upper low over the central High Plains at 12Z Saturday should
pivot northeastward towards the Upper Midwest as it becomes an open
wave. A belt of strong mid-level southwesterlies should overlap with
the northwestern periphery of a modified low-level moisture plume
emanating north from the western Gulf. This plume is expected to be
narrower to the north-northwest of the Ark-La-Tex. Combined with
probable ongoing convection in the warm conveyor ahead of the weak
surface front, the overall severe threat on D4 should be
confined/low-end.

While outlier guidance indicates the possibility of TC Rafael
approaching the coastal LA vicinity this weekend, ensemble trends
and latest NHC forecast suggest it will probably remain over the
western Gulf.

Guidance consensus still indicates an amplified upper trough should
progress into the West early next week, with this feature reaching
the central states mid-week. This may eventually overlap a
broadening warm/moist sector emanating north from the western Gulf
across the south-central states. But poor run-to-run continuity and
large ensemble spread persist with the evolution of this trough.

..Grams.. 11/06/2024

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ACUS48 KWNS 070956
SWOD48
SPC AC 070955

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0355 AM CST Thu Nov 07 2024

Valid 101200Z - 151200Z

...DISCUSSION...
...D6-7/Tuesday-Wednesday...
Guidance consensus still indicates that an amplified upper trough
should progress into the West early next week, with this feature
reaching the central states mid-week. 00Z ensemble spread remains
large with multiple facets of the trough evolution and associated
cyclogenesis over the central states/southern Prairie Provinces. In
addition, the breadth of rich western Gulf moisture being drawn
north is uncertain. It will likely be dependent on the degree of
preceding surface ridging into the northern Gulf. The deterministic
ECMWF does appear bullish on a potential severe threat in parts of
the south-central states. This will be monitored for greater
predictability in later outlooks.

..Grams.. 11/07/2024

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ACUS48 KWNS 080840
SWOD48
SPC AC 080839

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0239 AM CST Fri Nov 08 2024

Valid 111200Z - 161200Z

...DISCUSSION...
Guidance consensus continues to indicate a broad upper trough
progressing into the West early next week, and then reaching the
central states around mid-week. Nevertheless, 00Z ensemble spread
remains large with both the degree of trough amplification and
spatiotemporal details. The GEFS has trended towards less
amplification over the West, instead favoring later over the Upper
Midwest. The ECMWF ensemble mean favors greater amplification over
the West, which is supported by its deterministic parent and
UKMET/CMC guidance. Run-to-run continuity is poor with the
degree/location of cyclogenesis east of the Rockies.

With greater confidence in a surface ridge holding across the
northern Gulf, modified moisture return appears more likely to be
limited in the southern to central Great Plains through D5/Tuesday.
The breadth of the warm-moist sector will probably enlarge by
D6/Wednesday, yielding concern for some severe potential over the
south-central states. But given poor predictability of
synoptic-scale details, consideration of an area is premature.

..Grams.. 11/08/2024

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ACUS48 KWNS 090947
SWOD48
SPC AC 090945

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0345 AM CST Sat Nov 09 2024

Valid 121200Z - 171200Z

...DISCUSSION...
Guidance agreement has increased with regard to poor-quality
moisture return ahead of an upper trough ejecting from the West into
the central states on D4-5/Tuesday-Wednesday. A preceding surface
ridge into the Gulf Coast region appears likely to inhibit
appreciable poleward advection of Gulf moisture through D5. While
differences remain in the evolution of the upper trough, guidance
has markedly shifted north with cyclogenesis centered on the
northern Great Plains. This setup appears unlikely to support an
organized severe threat.

Late week, the next broad upper trough has above-average agreement
in reaching the West Coast. Guidance indicates potentially greater
low-level moisture return from the western Gulf into the southern
Great Plains. This suggests at least a low-probability severe threat
may occur next weekend, as indicated by both SPC and NSSL GEFS-based
ML guidance, which appears supported by the 00Z ECMWF ensemble mean. Predictability is low with the evolution of embedded shortwave
impulse within this large-scale trough.

..Grams.. 11/09/2024

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ACUS48 KWNS 100926
SWOD48
SPC AC 100924

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0324 AM CST Sun Nov 10 2024

Valid 131200Z - 181200Z

...DISCUSSION...
Predictability concerns that are evident on D3/Tuesday appear to
affect the extended period. Non-GEFS/GFS models support a
slower/southward evolution of a shortwave trough across the central
states into the East on D4-5/Wednesday-Thursday. The 00Z
deterministic ECMWF/UKMET are quite similar with this scenario.
While the surface cyclone reflection may be weak, rich Gulf moisture
coupled with an increase in low-level flow may be sufficient for at
least a low-probability severe threat centered on the Lower MS
Valley to the northeast Gulf Coast/southern Deep South.

Late week, there continues to be above-average agreement with a
positive-tilt longwave trough developing from the Canadian Prairies
to off the southern CA coast. Despite typical predictability
concerns with the handling of embedded shortwave impulses, the
primary impactful difference is with the degree of moisture return
across the Great Plains. Non-GEFS/GFS models have trended towards poorer-quality return flow in the wake of the leading shortwave
trough on D4-5 and subsequent continental air mass intrusion into
the Gulf. As such, despite SPC and NSSL GEFS-based ML guidance
depicting 5-15 percent severe probabilities next weekend, other
models seemingly suggest a 5 percent or less threat for now.

..Grams.. 11/10/2024

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ACUS48 KWNS 110958
SWOD48
SPC AC 110956

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0356 AM CST Mon Nov 11 2024

Valid 141200Z - 191200Z

...DISCUSSION...
A shortwave trough should exit the Lower to Mid-Atlantic Coast on
D4/Thursday, with amplification discrepancies from D3 persisting.
The 00Z ECMWF appears to be the remaining holdout of the
deterministic guidance for a low-probability severe threat in the
northeast Gulf Coast vicinity. Still, even it suggests low-level
flow should both decrease and become veered through the day, where
rich low-level moisture exists. Instability appears likely to be
meager and overall severe potential appears low.

The next broad mid/upper trough should progress into the West by
D5/Friday. Guidance appears to be coalescing towards two distinct
shortwave impulses evolving within this longwave pattern. The lead
one is progged to track northeast into the northern Great Plains and
then pivot east across the Upper Midwest/south-central Canada over
the weekend. Meanwhile, a basal shortwave impulse should become
established off the southern CA coast. This may gradually move east
over the Desert Southwest and northwest Mexico late in the period.

Guidance continues to differ with the degree of continental airmass
intrusion into the northern Gulf, in the wake of the shortwave
trough departing the East on D4. Overall trends and likelihood of
surface ridging persisting across parts of the Gulf Coast suggest
that returning moisture will probably be of low quality in advance
of the north-central states wave. However, this may yield multiple
days of return flow and an increasingly moist warm sector becoming
established over the southern Great Plains by D8/Monday.

SPC GEFS-based ML guidance has trended down to a 2 percent
probability for D6/Saturday, after depicting a 15 percent area
yesterday. It has instead, increased probabilities to 15 percent on
D7/Sunday. Meanwhile, NSSL GEFS-based ML guidance has decreased
probabilities for D7 from 10 percent yesterday to 5 percent today.
Both of these are 5 percent or less on D8, when the ECMWF ensemble
mean would be more indicative of 15 percent potential. Given the
lack of consistency, a severe weather highlight for D7 or D8 appears
premature but bears watching in later cycles.

..Grams.. 11/11/2024

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ACUS48 KWNS 120935
SWOD48
SPC AC 120933

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0333 AM CST Tue Nov 12 2024

Valid 151200Z - 201200Z

...DISCUSSION...
Guidance still generally suggests some organized severe potential
may evolve across the south-central Plains and vicinity early next
week, though uncertainty remains high regarding the timing and
intensity of embedded shortwave troughs and the details regarding
low-level moisture return and destabilization.

On D5/Saturday, a mid/upper-level shortwave trough is forecast to
emerge from the deep, positively tilted trough over the West and
move across the northern Plains, accompanied by a deepening surface
low. While severe potential appears minimal on Saturday, the
ejecting wave is forecast to initiate low-level moisture return into
the southern Plains, which will continue into D6/Sunday and
D7/Monday.

For D6/Sunday into D7/Monday, the most important feature related to
severe potential will be a shortwave trough that may briefly evolve
into a closed mid/upper-level low somewhere over the Southwest,
before ejecting east-northeastward. Recent runs of the deterministic
ECMWF/GFS are in relatively good agreement in depicting a negatively
tilted shortwave trough ejecting into the south-central Plains on
D7/Monday. However, spread among GEFS ensemble members remains
rather high regarding the timing and evolution of shortwaves into
early next week, while the ECMWF is less aggressive with low-level
moisture return, showing only very minimal destabilization in
advance of the ejecting shortwave trough on D7/Monday.

Given the uncertainties regarding both shortwave timing and
magnitude of moisture return/destabilization, confidence is too low
to delineate a 15 percent area over some portion of the
south-central Plains for D7/Monday, the day which seems to have the
greatest relative potential at this time. It remains possible that
some severe threat could emerge as soon as D6/Sunday, and/or
potentially persist into D8/Tuesday.

..Dean.. 11/12/2024

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ACUS48 KWNS 131001
SWOD48
SPC AC 130959

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0359 AM CST Wed Nov 13 2024

Valid 161200Z - 211200Z

...DISCUSSION...
Some severe potential remains evident across parts of the
southern/central Plains (and potentially farther east) early next
week, though uncertainty remains regarding the most favored corridor
and the magnitude and sufficiency of low-level moisture/instability.

...D5/Sunday - D6/Monday...
On Saturday, a shortwave trough and attendant surface low are
forecast to move across the northern Great Plains. Low-level
southeasterly flow will result in early-stage moisture return into
the southern/central Plains, as a surface ridge shifts eastward
across the eastern CONUS. Meanwhile, a shortwave mid/upper-level
trough initially near the southern CA/Baja coast may evolve into a
closed upper-level low as it digs east-southeastward from late
Saturday into early Sunday. This trough/low is then forecast to
eject northeastward as a negatively tilted trough across parts of
the southern/central Plains from late Sunday into Monday,
accompanied by significant surface cyclogenesis.

The primary uncertainty regarding severe potential for D5/Sunday
into D6/Monday is the magnitude of low-level moisture return and destabilization across the warm sector of the developing surface
low. While low/mid 60s F dewpoints may return into parts of TX and
perhaps OK, with 50s F dewpoints farther north, limited heating and
relatively weak lapse rates will limit buoyancy, with the GFS/ECMWF
and their related ensembles suggesting MLCAPE of 500 J/kg or greater
may be confined to parts of central/south TX, with increasingly
limited buoyancy farther north.

Some severe potential could evolve on D5/Sunday, especially later in
the period when the ejecting shortwave trough may begin to impinge
on richer moisture from southwest into central TX. An intensifying
low-level jet may support development of widespread convection from
late on D5/Sunday into D6/Monday, with a strongly forced band of
convection potentially moving east-northeastward across a larger
portion of the southern/central Plains.

Despite the very limited instability that is currently anticipated
across much of the region, the intense wind fields and strong ascent
associated with the ejecting shortwave trough (as depicted by the
GFS/ECMWF and some ensemble members) could support an organized
severe threat within a low-CAPE/high-shear regime. Uncertainty
remains regarding the most favorable corridor, with the GFS/ECMWF
favoring parts of the southern/central Plains, while some ensemble
members favor a zone farther east from the ArkLaTex into the mid MS
Valley.

...D7/Tuesday - D8/Wednesday...
Some severe potential could continue into D7/Tuesday into parts of
the Midwest and Ohio Valley, though there may be a tendency for
stronger deep-layer flow and ascent to become increasingly displaced
from sufficient moisture and instability.

NHC is currently forecasting a high probability of tropical cyclone
formation late this week into the weekend across the central/western
Caribbean Sea. Predictability remains very low regarding the
possibility for this system to influence severe potential across the
Southeast toward the middle of next week.

..Dean.. 11/13/2024

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ACUS48 KWNS 141002
SWOD48
SPC AC 141000

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0400 AM CST Thu Nov 14 2024

Valid 171200Z - 221200Z

...DISCUSSION...
...D4/Sunday into D5/Monday...
Extended-range guidance generally agrees that a mid/upper-level
shortwave trough/closed low will move eastward across parts of the Southwest/northern Mexico through the day Sunday. This system will
eject northeastward as a negatively tilted shortwave trough Sunday
evening into Monday, accompanied by intense deep-layer flow fields
and significant surface cyclogenesis. Meanwhile, recent guidance has
trended toward somewhat richer low-level moisture return, with mid
to upper 60s F dewpoints spreading into parts of
southwest/central/north TX Sunday night into Monday, with at least
low 60s F dewpoints into parts of OK/KS.

Midlevel temperatures will remain relatively warm across the warm
sector, but there is greater confidence in at least modest
surface-based buoyancy (with MLCAPE of 500-1000 J/kg) developing
across parts of west/central TX Sunday night, accompanied by an
substantial increase in low-level and deep-layer shear. Isolated
severe storm potential cannot be ruled out by late afternoon into
early evening, but a notable increase in storm coverage is expected
Sunday night. Extensive convection may result in a tendency toward a linear/QLCS mode, but intense deep-layer flow and increasing
low-level shear will support a threat of severe wind gusts along
with some tornado potential. A 15% area has been added for
D4/Sunday, where intensifying flow is forecast to overlap sufficient instability amid as deep convection increases in coverage Sunday
night.

Some severe threat may persist from late D4/Sunday into at least
early D5/Monday, as the shortwave and attendant surface low continue
to eject northeastward. Uncertainty increases at this time range
regarding the northern and eastern extent of the severe threat on
D5/Monday, as richer low-level moisture potentially gets pinched off
from the stronger ascent from the ejecting shortwave trough, and
buoyancy becomes increasingly weak across the warm sector. Intense
wind fields will support some severe-wind and tornado potential
where convection can remain surface-based. There also may be some
potential for renewed storm development Monday afternoon in the
immediate vicinity of the ejecting shortwave and surface low across
the central Plains (as suggested in the 14/00Z ECMWF), though this
scenario remains quite uncertain.

A small 15% area has been included for D5/Monday, as a continuation
of the threat that begins late D4/Sunday. Depending on
destabilization trends during the day on Monday, probabilities may
eventually need to be expanded to the north and/or east of this
area.

...D6/Tuesday - D8/Thursday...
Some severe threat could linger on D6/Tuesday in the vicinity of the
MS Valley, though model spread increases substantially at this range
regarding the evolution of the upper-level pattern and occluding
cyclone over the northern Plains/upper Midwest. Otherwise, Tropical
Depression 19 has formed across the Caribbean, with the NHC forecast
track suggesting this system may eventually approach some portion of
the Gulf of Mexico. Uncertainty remains very high regarding any
severe threat with this system into mid/late next week.

..Dean.. 11/14/2024

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ACUS48 KWNS 150940
SWOD48
SPC AC 150938

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0338 AM CST Fri Nov 15 2024

Valid 181200Z - 231200Z

...DISCUSSION...
...Monday/Day 4 to Wednesday/Day 6...
A negatively-tilted mid-level trough is forecast to move quickly
northeastward across the southern Plains on Monday. A cluster of
strong to severe thunderstorms is expected to be ongoing at the
start of the period over north-central Texas and southern Oklahoma.
A few severe wind gusts will be possible in this area Monday
morning. Thunderstorm development may continue ahead of the trough
during the day from east Texas and the Sabine River Valley northward
into eastern Oklahoma, eastern Kansas, the Ozarks and lower to mid
Missouri Valley. An isolated potential for severe gusts will be
possible but instability is expected to remain minimal.

On Tuesday, a mid-level trough is forecast to move eastward into the
southern Plains, as southwest mid-level flow remains over the Ohio
and Tennessee Valleys. A cold front is forecast to move eastward
into the lower Mississippi and Tennessee Valleys. Thunderstorm
development will be possible during the day along and ahead of the
front. Any severe threat ahead of the front is expected to be
isolated due to limited instability.

On Wednesday, an upper-level low is forecast to move into the Ohio
Valley, as a cold front advances eastward toward the southern
Atlantic Seaboard. The greatest potential for isolated severe storms
would be ahead of the front in the Carolinas, and across parts of
Florida.

...Thursday/Day 7 and Friday/Day 8...
The upper-level low is forecast to move eastward from the central
Appalachians on Thursday to the western Atlantic on Friday. The
airmass across the continental U.S. is expected to be relatively dry
making conditions unfavorable for thunderstorm development across
most of the continental U.S.

..Broyles.. 11/15/2024

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ACUS48 KWNS 160944
SWOD48
SPC AC 160943

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0343 AM CST Sat Nov 16 2024

Valid 191200Z - 241200Z

...DISCUSSION...
...Tuesday/Day 4 and Wednesday/Day 5...
A mid-level trough is forecast to move into the Great Plains on
Tuesday, as a cold front advances eastward into the Ohio and
Tennessee Valleys. Thunderstorms are expected to develop ahead of
the front during the day. An isolated potential for severe gusts
will be possible within a moist airmass across parts of the central
Gulf Coast States.

On Wednesday, the trough is forecast to move into the Ohio and
Tennessee Valleys, as the front advances eastward into the Carolinas
and north Florida. Isolated strong to severe gusts will be possible
with storms that develop along and ahead of the front, but the
threat should be marginal due to weak instability.

...Thursday/Day 6 to Saturday/Day 8...
From Thursday to Saturday, a mid-level low is forecast to move from
the Ohio Valley eastward into the western Atlantic. Thunderstorm
development will be possible Thursday afternoon ahead of the system
in the parts of the Northeast. A dry and relatively stable airmass
across the continental U.S. on Friday and Saturday should limit
thunderstorm potential in most areas.

..Broyles.. 11/16/2024

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ACUS48 KWNS 170941
SWOD48
SPC AC 170940

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0340 AM CST Sun Nov 17 2024

Valid 201200Z - 251200Z

...DISCUSSION...
...Wednesday/Day 4...
An upper-level trough is forecast to move through the Ohio and
Tennessee Valleys on Wednesday as a cold front advances eastward
through the southern and central Appalachians. Ahead of the front,
surface dewpoints are forecast to be in the 60s F across much of the
Carolinas into Virginia. Thunderstorms could develop ahead of the
front during the day from the Mid Atlantic southward into the
Carolinas, but instability is forecast to be very weak suggesting
that any severe threat will remain marginal.

...Thursday/Day 5 to Sunday/Day 8...
A dry and relatively stable airmass is forecast to be in place
across the continental U.S. from Thursday through the weekend. As a
result, severe thunderstorms are not expected during this period.

..Broyles.. 11/17/2024

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ACUS48 KWNS 180941
SWOD48
SPC AC 180939

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0339 AM CST Mon Nov 18 2024

Valid 211200Z - 261200Z

...DISCUSSION...
A mid-level trough is forecast to move into the western Atlantic
Thursday night, as a mid-level ridge builds over the western U.S.
The ridge is forecast to gradually move eastward across the U.S.
from this weekend into early next week. A relatively dry airmass is
forecast over most of the continental United States through
Saturday, suggesting that thunderstorms will be unlikely. Low-level
moisture is forecast to advect northward into the Ark-La-Tex on
Sunday and into the mid Mississippi Valley on Monday. Within this
moist airmass, isolated storms will be possible. However,
instability is forecast to be limited suggesting a severe threat
will be minimal.

..Broyles.. 11/18/2024

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ACUS48 KWNS 190951
SWOD48
SPC AC 190950

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0350 AM CST Tue Nov 19 2024

Valid 221200Z - 271200Z

...DISCUSSION...
A relatively stable weather pattern will persist for much of the
Fri/D4 through Tue/D8 period, owing to a large upper trough over the
East and a ridge over the West. Low-level moisture across the CONUS
will with not return with any abundance until around Mon/D7. At that
time, models indicate a broad belt of west to southwest flow aloft
with general troughiness across the West, and rising heights
possibly over the East. Mid to upper 60s F are forecast from eastern
TX into the lower MS Valley, beneath increasing flow aloft which
could potentially yield areas of strong storms in the warm advection
regime.

..Jewell.. 11/19/2024

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ACUS48 KWNS 200906
SWOD48
SPC AC 200905

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0305 AM CST Wed Nov 20 2024

Valid 231200Z - 281200Z

...DISCUSSION...
An upper trough will move out of the northeastern states from Sat/D4
into Sun/D5, with the ridge flattening over the Plains. This will
result in a broad belt of near zonal flow across much of the CONUS,
with perhaps a slight propensity for cyclonic height curvature over
the Great Lakes into eastern Canada.

Low-level moisture return will occur gradually, especially from
Mon/D6 onward when 60s dewpoints may extend from eastern TX into the
lower MS Valley. However, not until around Tue Night/D7 do most
models show any appreciable instability, and even then it will
likely be weak. As such, severe storms are not forecast. However, a
few strong storms cannot be ruled out by around Wed/D8 due to
several days of persistent moistening, especially if a shortwave
trough can amplify within the strong flow regime.

..Jewell.. 11/20/2024

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ACUS48 KWNS 210946
SWOD48
SPC AC 210945

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0345 AM CST Thu Nov 21 2024

Valid 241200Z - 291200Z

...DISCUSSION...
Models indicate a relatively strong zonal pattern over much of the
CONUS for Sun/D4 into Mon/D5, with a shortwave trough skirting the
Great Lakes area. Then, through the Thu/D8 period, there is a
possibility of a low-amplitude trough amplification within this
strong belt of flow, moving across the southern Plains and
Southeast.

Predictability for this later scenario is low at this time, as there
is little run-to-run consistency. However, the air mass over the
western Gulf of Mexico, spreading into the lower MS Valley, will
become progressively more moist and unstable each day, and severe
weather may become possible in those areas. The initial more robust
moisture return from southeast TX across LA and southern MS/AL may
be accompanied by substantial clouds and precipitation, but stronger destabilization will be possible as the warm front potentially moves
north into the Wed/D7 to Thu/D8 time frame.

..Jewell.. 11/21/2024

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ACUS48 KWNS 220939
SWOD48
SPC AC 220938

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0338 AM CST Fri Nov 22 2024

Valid 251200Z - 301200Z

...DISCUSSION...
Models are in good agreement with the general pattern on Mon/D4,
depicting a midlevel speed max nosing into the central Plains Monday
morning, then phasing with an upper trough over the northern Plains.
This should then result in an amplified shortwave trough moving
across the Midwest and Great Lakes through Tue/D5 morning. An
associated cold front will shunt the young moist plume back south
toward the Gulf Coast.

This trough is then expected to eject northeastward toward Quebec
into Tue/D5, with a zonal flow regime across the CONUS on Wed/D6,
with slow moisture return.

Beyond this time frame, subtle differences exist regarding how
quickly the pattern may amplify, as ridging occurs over the West,
and a possible trough develops from the southern Plains into the
southeastern states. Any appreciable low-level moisture return and destabilization would likely be tied to such a trough amplification,
which is low predictability. In short, a non-zero threat of severe
storms may develop over parts of the Gulf Coast states, Thu/D7 into
Fri/D8, as moisture increases and flow aloft remains strong.

..Jewell.. 11/22/2024

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ACUS48 KWNS 230922
SWOD48
SPC AC 230920

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0320 AM CST Sat Nov 23 2024

Valid 261200Z - 011200Z

...DISCUSSION...
On Tue/D4, an upper trough will pivot northeastward from the Great
Lakes into southern Quebec, with temporary zonal flow across much of
the CONUS. Moisture along the central Gulf Coast will be quickly
shunted offshore as a cold front pushes south.

Models are in good agreement depicting another shortwave trough over
the central Rockies on Wed/D5, with some amplification possible into
the southern Plains Wed night. This trough will maintain a positive
tilt on Thu/D6 with a 65-75 kt 500 mb speed max extending from TX to
the TN/OH Valleys by 00Z Fri/D7.

During the day on Wed/D5, low pressure is forecast to develop over
OK, and will translate east/northeast into KY/TN Wed night ahead of
a cold front. South of this front, a relatively large area of mid to
upper 60s F dewpoints will develop, especially Wed night, from
eastern TX across LA and MS. Given the positive tilt of the upper
trough, winds around 850 mb will be out of the west/southwest,
reducing low-level shear somewhat. In addition, speeds are not
expected to be particularly strong. Still, thunderstorms will likely
develop late Wed/D5 over the lower MS and TN Valleys near the cold
front. Greater thunderstorm coverage is expected on Thu/D6 over much
of the Southeast and ahead of a strengthening cold front. Even with
veered low-level winds, the strong deep-layer shear and focus along
the front may provide a risk of severe/wind storms. This area will
be monitored for upgrades in later outlooks as predictability
increases.

From Fri/D7 into Sat/D8, a secondary speed max moving out of the
upper MS Valley/Great Lakes will likely phase with the southern
trough, eventually enveloping the eastern CONUS, and reinforcing
stable air behind the cold front.

..Jewell.. 11/23/2024

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ACUS48 KWNS 240933
SWOD48
SPC AC 240932

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0332 AM CST Sun Nov 24 2024

Valid 271200Z - 021200Z

...DISCUSSION...
Run-to-run model trends indicate generally faster solutions to the
evolving upper trough forecast to move across the central and
eastern CONUS.

On Wed/D4, a positive-tilt upper trough will extend from the upper
MS Valley into the Plains, with 500 mb speed max over 70 kt. This
feature is now forecast to be over the OH/TN Valley by 12Z Thu/D5,
with attendant cold front roughly from WV to southern MS/LA at that
time.

Given this trough speed and geometry, winds around 850 mb will be west-southwest to west at 40-50 kt. Elevated thunderstorms seem
likely given the antecedent dry air mass in place ahead of the
returning low-level moisture, most notably from KY/TN southward into
northern MS/AL/GA through 12Z Thu/D5. Surface-based storms may
develop across southern areas late along the front, with non-zero
damaging-gust potential given substantial deep-layer shear and wind
magnitude.

ECMWF-based solutions indicate much less storm coverage going into
Thu/D5 as the front accelerates across the Southeast, though some
lingering storms may be ongoing along the front early. Given these
trends, no severe areas will be issued.

..Jewell.. 11/24/2024

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ACUS48 KWNS 250938
SWOD48
SPC AC 250937

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0337 AM CST Mon Nov 25 2024

Valid 281200Z - 031200Z

...DISCUSSION...
For the Thu/D4 to Fri/D5 period, an upper trough over the MS/OH/TN
Valleys will continue to amplify, aided by a backside speed max
moving from the northern Plains toward the OH Valley. Given the
phasing aspect of this setup, models show appreciable variability
with timing and location of the resulting large trough, and surface
low position. However, the primary facet to severe potential will be
the less-than-optimal warm sector which will exist ahead of the cold
front.

GFS members are slower with both the front and the upper trough as
compared to ECWMF, which has the front offshore by Thu/D4 evening.
In either case, strongly veering 850 mb winds and associated drying
will impact severe potential. While predictability is currently low
due to large model spread, potential does exist for scattered strong
storms, primary over parts of AL and GA on Thursday. However, a
faster model solution could result in minimal threat over land,
except perhaps far eastern GA and the Carolinas. As such, trends
will be monitored in coming days for potential risk areas.

After this front moves offshore late Thursday, the remainder of the
period will see a relatively cool and stable pattern, with strong
northwest flow aloft persisting across the Plains, and periodic
surges of high pressure.

..Jewell.. 11/25/2024

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ACUS48 KWNS 260904
SWOD48
SPC AC 260902

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0302 AM CST Tue Nov 26 2024

Valid 291200Z - 041200Z

...DISCUSSION...
...D4/Friday...
While guidance continues to vary regarding frontal timing, even the
slower solutions have the front near or off of the Carolina coast by
12Z Friday. The trailing portion of the front will move across the
Florida Peninsula during the day. Some overlap of strong deep-layer
shear and modest instability may develop along/ahead of the front
across the peninsula, but a general weakening of large-scale ascent
with time could limit potential for robust storm development.

...D5/Saturday - D8/Tuesday...
Extended-range guidance generally depicts a persistent large-scale mid/upper-level trough over the eastern CONUS from Saturday through
Tuesday, as multiple reinforcing shortwave troughs move
southeastward from Canada. A large and persistent surface ridge is
expected to inhibit low-level moisture return from the Gulf of
Mexico, resulting in low severe potential from this weekend into
early next week.

..Dean.. 11/26/2024

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ACUS48 KWNS 270902
SWOD48
SPC AC 270900

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0300 AM CST Wed Nov 27 2024

Valid 301200Z - 051200Z

...DISCUSSION...
Severe-thunderstorm potential still appears low through the extended
range. An upper-level trough is expected to persist across the
eastern CONUS through the period, as multiple reinforcing shortwaves
move southeastward from Canada. A surface ridge covering much of the central/eastern CONUS will inhibit low-level moisture return through
most of the extended range. Guidance suggests potential for the
surface ridge to eventually shift eastward by D7/Tuesday into
D8/Wednesday, allowing for some moisture return into parts of Texas.
This could lead to an increase in thunderstorm activity, but the
displacement between stronger deep-layer flow/shear and any
appreciable surface-based instability currently appears too large to
support organized severe potential through early next week.

..Dean.. 11/27/2024

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ACUS48 KWNS 280908
SWOD48
SPC AC 280906

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0306 AM CST Thu Nov 28 2024

Valid 011200Z - 061200Z

...DISCUSSION...
Organized severe-thunderstorm potential still appears low through
most of the extended range.

A deep upper-level trough is expected to persist across the
central/eastern CONUS into at least the middle of next week, as
multiple reinforcing shortwaves move southeastward out of Canada. In conjunction with this trough, surface ridging will persist across
the Gulf of Mexico and generally maintain dry and stable conditions
for most of the CONUS. Farther west, a slow-moving mid/upper-level
trough may gradually amplify and potentially become a cut off low in
the vicinity of the Desert Southwest into northwest Mexico and Baja
California.

Guidance does suggest that gradual low-level moisture return will be
possible across parts of TX/LA from D4/Sunday into early next week,
as the surface ridge shifts eastward. This moisture return could
result in occasional thunderstorm potential within a weak
warm-advection regime, though the synoptic pattern is expected to
remain unfavorable for an organized severe threat.

By mid week, predictability regarding the synoptic pattern
substantially decreases, especially regarding if/when the potential
cut-off low begins to eject eastward across the Southwest and
southern Rockies. A faster ejection could result in some possibility
for more-organized convection across the southern Plains by late
next week, though the bulk of guidance still suggests generally low
potential through at least D7/Wednesday.

..Dean.. 11/28/2024

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ACUS48 KWNS 290800
SWOD48
SPC AC 290758

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0158 AM CST Fri Nov 29 2024

Valid 021200Z - 071200Z

...DISCUSSION...
The large-scale pattern during the Day 4-8 period will be
characterized by a series of upper troughs impacting the eastern
half of the CONUS. Meanwhile, a cut-off low within the broader
western upper ridge will persist off the southern CA and Baja
coasts.

Some thunderstorm activity is possible across parts of Texas around
Days 4-5/Mon-Tue and portions of LA/southern MS into midweek. Modest
southerly return flow ahead of a southeast-advancing cold front will
bring 60s F dewpoints into the western/central Gulf Coast vicinity
as an upper shortwave trough and surface low moves from the northern
Plains through the Midwest. Large-scale ascent will remain displaced
well to the north and destabilization is expected to be very modest,
precluding severe potential.

Otherwise, cool and stable conditions will prevail across much of
the CONUS, and thunderstorm activity will be low.

..Leitman.. 11/29/2024

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ACUS48 KWNS 300958
SWOD48
SPC AC 300956

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0356 AM CST Sat Nov 30 2024

Valid 031200Z - 081200Z

...DISCUSSION...
A series of upper-level troughs will move across the northern
Plains, Great Lakes and Northeast U.S. during the Day 4-8 time
frame. Farther west, an upper low initially near the West Coast will
move slowly east across the southwest states/northern Mexico.
Low-level moisture will gradually increase from east TX eastward
across the central Gulf Coast Tuesday/D4-Thursday/D6, however latest
GEFS and ECMWF ensemble guidance reflects only weak instability
across this area and with large-scale lift remaining displaced well
to the north. Although some thunderstorm potential may ultimately
exist within this environment, the severe weather potential remains
low. Thereafter, very limited instability suggests continued low
severe potential through the remaining outlook period.

..Bunting.. 11/30/2024

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ACUS48 KWNS 010716
SWOD48
SPC AC 010715

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0115 AM CST Sun Dec 01 2024

Valid 041200Z - 091200Z

...DISCUSSION...
A strong upper-level trough will move off the East Coast toward the
middle of this week. Additional reinforcing troughs are forecast in
its wake through the end of this week and potentially into next
weekend. This will keep a dry, continental polar airmass across the
eastern CONUS through the extended period.

Some low-level moisture will slowly drift inland across Texas and
potentially the central Gulf coast by the end of the week, however
this will likely be quickly shunted offshore with the arrival of
another cold front before any appreciable instability can develop.
Therefore, a few thunderstorms are possible along the Gulf Coast,
but minimal instability should limit any severe weather threat.

..Bentley.. 12/01/2024

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ACUS48 KWNS 020856
SWOD48
SPC AC 020855

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0255 AM CST Mon Dec 02 2024

Valid 051200Z - 101200Z

...DISCUSSION...
A strong cold front will move into the Gulf on Thursday morning with
a dry, continental polar airmass to spread across the eastern CONUS
in its wake. This will keep thunderstorm activity limited to far
south Texas late this week and into the early part of the weekend.
Eventually, the moist sector will advect inland across Texas and the
ArkLaTex ahead of an approaching mid-level trough late on Saturday
and on Sunday. The associated cold front will likely trigger some
thunderstorm activity on Sunday and Monday. However, instability
appears quite limited at this time, and therefore, a substantial
severe weather threat appears unlikely during the Day 4 to 8 period.

..Bentley.. 12/02/2024

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ACUS48 KWNS 030804
SWOD48
SPC AC 030802

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0202 AM CST Tue Dec 03 2024

Valid 061200Z - 111200Z

...DISCUSSION...
Significant low-level moisture will remain offshore through the
middle of the weekend. However, by Sunday and especially Monday, the
GFS and ECMWF both show mid 60s dewpoints inland perhaps as far
north as the Mid-Mississippi Valley. Once this moisture moves
inland, some severe weather is possible. Greatest concern at this
time is Day8/Tuesday as both the ECMWF and GFS (as well as their
ensemble mean) have a strong, positively tilted mid-level trough
moving into the southern Plains with surface cyclogenesis. Despite
the mid 60s dewpoints inland, current forecast instability from the
ECMWF and GFS remains quite weak. This combined with uncertainty
regarding timing and evolution of the trough precludes any
significant severe weather concern at this time. However, this
period will continue to be monitored as the details become more
clear.

..Bentley.. 12/03/2024

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ACUS48 KWNS 040830
SWOD48
SPC AC 040829

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0229 AM CST Wed Dec 04 2024

Valid 071200Z - 121200Z

...DISCUSSION...
After an extended period with troughing in the eastern CONUS and
ridging across the west, a pattern change is expected starting this
weekend. Ridging will start to build into the Southeast with a
series of troughs moving through the western CONUS as a more
progressive pattern evolves. As ridging builds across the Southeast,
the surface pattern will result in favorable trajectories for
significant moisture recovery across the Gulf of Mexico. Some of
this richer moisture will likely advect inland across portions of
the Gulf Coast and Southeast early next week. The inland moisture
intrusion combined with the arrival of several troughs within a
progressive pattern would suggest the potential for some severe
weather. However, there still remains uncertainty in the upper-level
pattern with an elongated, positively tilted trough from the GFS
which lacks significant cyclogenesis. In contrast, the ECMWF
eventually has a negatively tilted trough emerge from the western
trough with a surface cyclone, but it strengthens much later across
the Great Lakes with much of the mass response disconnected from the
better low-level instability.

Will continue to monitor the severe weather potential early next
week, but uncertainty remains too high to highlight any specific
periods at this time.

..Bentley.. 12/04/2024

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ACUS48 KWNS 050900
SWOD48
SPC AC 050859

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0259 AM CST Thu Dec 05 2024

Valid 081200Z - 131200Z

...DISCUSSION...
Ridging will start to build into the Southeast this weekend with a
series of troughs moving through the western CONUS as a more
progressive pattern evolves. As ridging builds across the Southeast,
the surface pattern will result in favorable trajectories for
significant moisture recovery across the Gulf of Mexico. Some of
this richer moisture will likely advect inland across portions of
the Gulf Coast and Southeast early next week. The inland moisture
intrusion combined with the arrival of several troughs within a
progressive pattern would suggest the potential for some severe
weather. However, there still remains uncertainty in the upper-level
pattern and the degree of destabilization.

The ECMWF shows a sharpening trough moving across east Texas late
Sunday. A strengthening low-level jet will be associated with this
trough with increasing low-level moisture across parts of East Texas
and Louisiana. However, instability is forecast to remain quite weak
with a mostly moist-adiabatic thermodynamic environment in the
region. Some severe weather could be possible in this scenario, but
the weak instability will likely preclude a greater threat. The GFS
shows more of a closed low moving into the central Plains with
forcing further displaced from the better low-level moisture and
thus minimal severe weather potential on Day4/Sunday.

Beyond Day 4 there will be some severe weather potential as a large
trough crosses the western CONUS and digs into the southern Plains
with moisture inland across the Gulf Coast and Southeast. A wide
range of possibilities remain due to the complicated upper-level
pattern and variance among forecast guidance. Therefore, there are
no specific periods with greater severe weather concern, but the
extended range will need to be monitored given the presence of an
approaching large-scale trough and inland 60F+ dewpoints.

..Bentley.. 12/05/2024

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