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Mesoscale Discussion 1239
NWS Storm Prediction Center Norman OK
0559 PM CDT Mon Jun 20 2022

Areas affected...parts of northeastern Nebraska...southeastern South
Dakota and adjacent southwestern Minnesota

Concerning...Severe potential...Watch unlikely 

Valid 202259Z - 210100Z

Probability of Watch Issuance...20 percent

SUMMARY...c*nvection capable of producing strong to severe surface
gusts may continue to develop and overspread the region through 8-10
PM CDT.  A new severe thunderstorm watch is not currently
anticipated, but additional counties across southeastern South
Dakota and southwestern Minnesota may be added to WWs 394 and 395.

DISCUSSION...A small, but persistent area of thunderstorms spreading
to the west/northwest of Yankton SD may have initiated in response
to forcing associated with lower/mid tropospheric warm advection,
within a strongly heated and deeply mixed boundary layer. This
environment extends in a narrowing pre-cold frontal corridor
northeast of the Missouri River into west central Minnesota, and is
beco*ing a focus for increasing convective development as mid-level
inhibition weakens in response to daytime heating.  

Upper 60s F dew points appear to be contributing to a corridor of
moderate CAPE in excess of 2000 J/kg downstream of the evolving
cluster, which may maintain thunderstorm development into the 01-03Z
time frame.  Although stronger mid/upper flow and deep-layer shear
are generally confined to the post-frontal regime, the more
favorable thermodynamic regime is generally aligned with a 30-35 kt
southerly 850 mb jet.  This is forecast to strengthen into early
evening.  As it does, substantive sub-cloud evaporative cooling and
downward mixing of momentum may contribute to increasing potential
for strong to locally severe surface gusts.

..Kerr/Edwards.. 06/20/2022

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

ATTN...WFO...MPX...FSD...OAX...ABR...

LAT...LON   43409800 44359742 45589609 44229617 42749796 43409800