ACUS01 KWNS 121150
SWODY1
SPC AC 121148

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0648 AM CDT Tue Aug 12 2025

Valid 121300Z - 131200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE UPPER GREAT LAKES/MIDWEST...AND PORTIONS OF THE SOUTHWEST...

...SUMMARY...
Strong to occasionally severe thunderstorms may impact parts of the
upper Great Lakes/Midwest today with both damaging winds and hail
possible. Gusty winds may also occur over southeast Arizona and
southwest New Mexico.

...Great Lakes/Midwest...
A band of thunderstorms associated with an MCV tracked northeastward
across parts of IA into northern IL and southern WI early this
morning while remaining mostly sub-severe. Still, there may be some
potential for strong to locally damaging winds with this activity as
it continues northeastward across Lake Michigan into parts of Lower
MI this morning/early afternoon as daytime heating gradually
destabilizes the boundary layer. Otherwise, additional convection
should develop later this afternoon along/ahead of a weak front over
parts of WI and the U.P. of MI as the southern portion of a
mid/upper-level trough moves eastward over the Upper Midwest/Great
Lakes. Instability is forecast to remain fairly modest ahead of the
front, but enough deep-layer shear should exist to support some
organized convection. Initial cells may be capable of producing
marginally severe hail, before clustering potentially increases the
threat for occasional strong to damaging winds.

A separate area of thunderstorms is forecast to develop this
afternoon farther south and ahead of the front from portions of the
Midwest into Lower MI. While this region will have relatively weaker
mid-level westerly flow and related deep-layer shear compared to
locations farther north, greater low-level moisture and instability
are expected to be present. As low-level lapse rates become
steepened with diurnal heating of the moist airmass, loosely
organized clusters may become capable of producing isolated damaging
winds as they spread generally east-northeastward through the
afternoon and early evening.

...Southwest...
Strong daytime heating should encourage diurnally driven convection
over the higher terrain of southeast AZ and southwest NM this
afternoon. With weak flow aloft and negligible shear, thunderstorms
should drift slowly southward. Still, occasional gusty winds may
occur with the more robust convection given steepened lapse rates.

..Gleason/Leitman.. 08/12/2025

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