541
ACUS03 KWNS 290724
SWODY3
SPC AC 290722

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0222 AM CDT Sat Aug 29 2026

Valid 311200Z - 011200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
THE UPPER MISSISSIPPI VALLEY...

...SUMMARY...
Isolated severe thunderstorms, accompanied by wind and hail, are
possible Monday afternoon across parts of the Upper Mississippi
Valley.

...Synopsis...
A 500 mb anticyclone will become established over the central Plains
to the Mid-MS Valley on Monday, with a low-amplitude mid-level
shortwave trough poised to crest the ridge and impinge on the Upper
MS Valley. A surface trough will become established across the Upper
MS Valley/Midwest during the afternoon, promoting enough deep-layer
ascent for isolated thunderstorm development when also considering
the approach of the upper trough. Additionally, stronger mid-level
flow, accompanied by cooler temperatures aloft, will overspread a
moist boundary layer, supporting scattered strong to isolated severe
thunderstorms over portions of the Upper MS Valley.

...Portions of the Upper MS Valley...
The aforementioned low-amplitude mid-level trough will impinge on
the Upper MS Valley and support surface lee troughing by afternoon.
A diffuse warm front may also materialize roughly along the MN/IA
border into central WI. An appreciable EML will extend from the
central Rockies to the western Great Lakes, with up to 8 C/km
mid-level lapse rates possible. These lapse rates will overspread
mid 70s F dewpoints, yielding over 3000 J/kg MLCAPE on a widespread
basis, especially near the warm front. Given the possibility of an
increasing low-level jet beneath 30-50 kt 500 mb flow, elongated
hodographs with 40+ kts of effective bulk shear are possible. Such
conditions would favor supercellular development, with at least
severe wind and hail possible. However, storm coverage remains in
question since the strongest deep-layer ascent accompanying the
low-amplitude upper trough will only graze the warm frontal zone to
the north. Higher severe probabilities may be needed pending greater
confidence in higher storm coverage.

..Squitieri.. 08/29/2026

$$