ACUS01 KWNS 191246
SWODY1
SPC AC 191245

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0745 AM CDT Sat Jul 19 2025

Valid 191300Z - 201200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE NORTHERN/CENTRAL PLAINS...MIDWEST/GREAT LAKES...AND
VIRGINIA/NORTH CAROLINA...

...SUMMARY...
Scattered damaging winds are possible today across parts of the
Midwest/Great Lakes and southern Mid-Atlantic. Scattered large to
very large hail and severe gusts are possible across the
northern/central Plains during the late afternoon and evening.

...Midwest/Great Lakes...
A small thunderstorm cluster ongoing this morning across
southern/eastern IA should continue to track east-southeastward
along an instability gradient across parts of northern MO, IL, and
perhaps IN into at least the early afternoon. With sufficient
organization and evidence of a cold pool, this cluster may pose a
threat for strong to locally damaging winds. Reference Mesoscale
Discussion 1719 for more details. The potential for additional
strong to severe thunderstorms across the Midwest and Great Lakes
regions remains somewhat unclear given rather nebulous/weak forcing
aloft. Stronger westerly mid-level flow associated with upper
troughing over eastern Canada should tend to remain mostly displaced
to the north of the surface warm sector. Still, daytime heating of a
moist low-level airmass will likely encourage the development of
moderate to locally strong instability by early to mid afternoon
away from convective influences.

Somewhat stronger flow aloft and related deep-layer shear should be
present this afternoon across Lower MI. A mix of multicells and
marginal supercells may spread eastward from ongoing activity across
WI, or develop separately over this area while posing a threat for
isolated severe hail and damaging winds. Farther south into the
Midwest/OH Valley, weaker deep-layer shear and the bulk of
convection-allowing model guidance suggests that multicell clusters
should be the main convective mode. One or more of these clusters
will probably persist from the ongoing activity this morning, or
develop this afternoon along its outflow. Scattered severe/damaging
winds will likely be the main threat as these thunderstorms move
east-southeastward this afternoon into early evening across much of
the OH Valley/Midwest. This convection should eventually weaken this
evening as it encounters a less unstable airmass across the Lower
Great Lakes and central Appalachians.

...Virginia/North Carolina...
The Mid-Atlantic region will once again reside between upper
troughing to the north over the Northeast/eastern Canada, and a
mid/upper-level anticyclone anchored over the Southeast. The primary
synoptic front remains draped generally east-west along/near the
MD/PA/DE border. A very moist low-level airmass remains in place to
the south of this boundary, with surface dewpoints generally in the
low to mid 70s. A similar convective scenario to yesterday is
forecast again today. Diurnal heating of this moist airmass will
likely encourage moderate to locally strong MLCAPE by early
afternoon, even though mid-level lapse rates are expected to remain
poor. Around 15-25 kt of mid-level westerly flow should enable
thunderstorms that initially develop over the Appalachians/Blue
Ridge to advance eastward towards the lower elevations/coastal
regions of VA/NC this afternoon and early evening. Scattered
damaging winds should be the main threat with loosely organized
multicells/clusters. Isolated hail may occur with the stronger cores as well.

...Northern/Central Plains...
An upper trough/low is expected to persist today over western
Canada. On the southern periphery of this feature, a weak mid-level
shortwave trough should move eastward across the northern
Rockies/High Plains through this evening. Weaker mid-level westerly
flow will remain farther south into the central High Plains. At the
surface, a lee trough will extend southward from eastern MT to
eastern CO. Generally low to mid 60s surface dewpoints should exist
this afternoon along/east of the lee trough, with greater low-level
moisture present near a remnant front/boundary in NE. Isolated
thunderstorms across northeast MT may pose an isolated hail threat
this morning. Current expectations are for scattered thunderstorms
to develop initially over the higher terrain of the northern/central
Rockies this afternoon, with additional development farther east
along the lee trough.

As this convection spreads eastward into a moderately to strongly
unstable airmass across the northern/central High Plains, it should
strengthen. Weak low-level winds are forecast to veer and increase
with height through mid/upper levels, supporting strong deep-layer
shear and the potential for supercells. Scattered large hail will be
possible with any supercells that can persist, with most guidance
indicating a greater concentration of severe thunderstorms across
eastern MT into western ND, and separately across western/central
NE. Given the presence of steep mid-level lapse rates and 40-50+ kt
of deep-layer shear, isolated very large hail appears possible. If
one or more clusters can develop from the initial supercells, then a
greater threat for severe gusts would be realized this evening with
eastward extent across the northern/central Plains. There is low
confidence in this scenario occurring, however.

..Gleason/Bentley.. 07/19/2025

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