ACUS11 KWNS 232008
SWOMCD
SPC MCD 232008=20
MEZ000-232245-

Mesoscale Discussion 1418
NWS Storm Prediction Center Norman OK
0308 PM CDT Mon Jun 23 2025

Areas affected...parts of northwestern Maine

Concerning...Severe potential...Watch unlikely=20

Valid 232008Z - 232245Z

Probability of Watch Issuance...20 percent

SUMMARY...Widely scattered strong to severe storms, including a
supercell or two, may cross the St. Lawrence Valley and at least
approach parts of northwestern Maine prior to 8 PM EDT, accompanied
by the risk for large hail and potential for a tornado. Although it
still appears unlikely that a severe weather watch will be needed,
trends will continue to be monitored for this possibility.

DISCUSSION...Near/just ahead of a mid-level perturbation associated
with a now dissipated thunderstorm cluster, isolated supercell
development appears underway across parts of southeastern Quebec,
roughly 100 miles or so to the northwest of Quebec City. Activity
appears to be forming just to the south of a warm frontal zone,
where surface dew points are near 70 F, and low-level hodographs
have become sizable beneath 30 kt west-southwesterly flow around 850
mb.

This is occurring beneath 40-50 kt west-northwesterly 500 mb flow,
around the northeastern periphery of the prominent mid-level high
centered near the southern Appalachians, contributing to a
southeastward propagation toward the St. Lawrence Valley, near
Quebec City. Additional thunderstorm development appears possible
over the next few hours in closer proximity to the frontal zone to
the north.=20=20

East of the St. Lawrence Valley, into northern New England, warming
and moistening of the boundary layer is ongoing along and south of
the northward developing warm frontal zone. Forecast soundings from
the Rapid Refresh suggest that this may include surface dew points
increasing to near or above 70 F, in the presence of enlarging, clockwise-curved low-level hodographs, across parts of northwestern
Maine prior to 00Z. Although the onset of nightfall contributes to
some uncertainty concerning the extent of boundary-layer
destabilization, there appears at least some potential for the
maintenance of supercells posing a risk for severe hail, and
potential for a tornado or two.

..Kerr/Thompson.. 06/23/2025

...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!5nEnGQoL1-_u8CBJJUK334nNH-ReHaKo2LK26XT5hpqDy0p2FMiZ43ZGWFwV8SjZVBEa-vShH= ZJJNvKAZFBSvT6YZeo$ for graphic product...

ATTN...WFO...CAR...

LAT...LON 48077206 48317112 47126858 46007040 46627112 47607240
48077206=20

MOST PROBABLE PEAK TORNADO INTENSITY...85-115 MPH
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN


=3D =3D =3D
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