ACUS11 KWNS 281931
SWOMCD
SPC MCD 281931=20
SDZ000-282230-

Mesoscale Discussion 1720
NWS Storm Prediction Center Norman OK
0231 PM CDT Sun Jul 28 2024

Areas affected...South Dakota

Concerning...Severe potential...Watch possible=20

Valid 281931Z - 282230Z

Probability of Watch Issuance...40 percent

SUMMARY...Thunderstorm coverage is beginning to increase across
western to northern South Dakota with scattered strong to severe
storms probable by late afternoon and early evening. Watch issuance
is possible this afternoon, but timing is uncertain.

DISCUSSION...Latest GOES imagery shows steady deepening of
convection along a cold front draped from northeast to western SD as
well as within the Black Hills. 19 UTC surface observations along
and south of the front report temperatures in the low 90s -
considerably warmer than anticipated by recent guidance by this
time, which implies that boundary-layer mixing (and an accompanying
erosion of MLCIN) is progressing more rapidly than expected. As
such, the recent convective trends should continue with additional
thunderstorm development probable in the coming hours. Although
moisture quality degrades with westward extent, easterly low-level
winds on the northern periphery of a surface low are elongating
hodographs with effective bulk shear values approaching 30-40 knots.
This will support a window for a supercell or two as initially
discrete cells develop over the Black Hills and/or along the front
across western SD. With time, a combination of storm motions largely
along the front and a 1-2 km deep boundary layer with nearly dry
adiabatic lapse rates will promote consolidating cold pools and
upscale growth into one or more clusters as convection propagates to
the east and into a more moist/buoyant air mass. An organized MCS
may emerge out of this activity this evening with the potential for
severe winds, possibly up to 75 mph. Somewhat weak synoptic-scale
forcing for ascent casts some uncertainty onto overall storm
coverage, which may favor more isolated cells with limited potential
for upscale growth and a more localized severe threat. Convective
trends will be monitored for the need for watch issuance this afternoon/evening.

..Moore/Gleason.. 07/28/2024

...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!4VVerF_O7XLGUp03r_VrfHRD4I4UL7JW99dy6ZFq-82OhnfwzOXpUt83f9OAtJ4MsPTbE8lhL= gZDH9AOX6qEAkAEEBw$ for graphic product...

ATTN...WFO...FSD...ABR...UNR...

LAT...LON 43550362 43860394 44210404 44410372 44570285 45150051
45280017 45419983 45459930 45429838 45359777 45279764
45069753 44829756 44459780 44219801 43939844 43689893
43509946 43419997 43330052 43270099 43280166 43270224
43420309 43550362=20


=3D =3D =3D
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