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Mesoscale Discussion 1791
NWS Storm Prediction Center Norman OK
0326 PM CDT Sat Sep 17 2022

Areas affected...Portions of extreme northeastern SD and
southeastern ND into northern MN

Concerning...Severe potential...Watch possible 

Valid 172026Z - 172230Z

Probability of Watch Issuance...60 percent

SUMMARY...A threat for large hail and severe winds should gradually
increase this afternoon. Watch issuance is possible.

DISCUSSION...20Z surface analysis shows a low centered over eastern
SD, with a front extending from this low across northern MN.
Low-level convergence is occurring across northeastern SD near the
front, with recent visible satellite imagery showing cumulus
beginning to beco*e agitated across this area. As modest ascent
associated with a low-amplitude shortwave trough overspreads
northern MN and vicinity this afternoon, at least isolated
thunderstorms are expected to gradually develop along/south of the
front. Some diurnal heating has occurred over this region, with
temperatures generally in the mid to upper 70s. A sufficiently moist
low-level airmass acting in concert with the daytime heating is
supporting 500-1000 J/kg of MLCAPE per latest mesoanalysis
estimates. Locally stronger instability, with MLCAPE up to 1500
J/kg, may develop over the next couple of hours with continued
heating.

Recent VWPs from KMVX show strengthening southwesterly winds with
height through mid levels in association with the shortwave trough,
and corresponding deep-layer shear around 30-40 kt will support
organized updrafts. Current expectations are for a mix of multicells
and a couple of supercells to gradually strengthen and pose a threat
for both large hail and severe wind gusts as they spread generally
eastward across parts of northern MN this afternoon and early
evening. Even though the low-level flow is forecast to remain fairly
weak, a brief tornado may still occur near the front. Some
uncertainty remains regarding overall coverage of this potentially
robust convection given the weak large-scale forcing aloft. But,
observational trends will be monitored for possible watch issuance
in the next couple of hours.

..Gleason/Grams.. 09/17/2022

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...DLH...MPX...FGF...ABR...

LAT...LON   45529653 45619696 45959692 47269543 47699402 47639359
            47349292 46599309 46159468 45809575 45529653