ZCZC SPCSWOMCD ALL
ACUS11 KWNS 222024 
SPC MCD 222024 
NDZ000-SDZ000-MTZ000-WYZ000-222230-

Mesoscale Discussion 1327
NWS Storm Prediction Center Norman OK
0324 PM CDT Thu Jul 22 2021

Areas affected...Parts of eastern Montana...northeastern Wyoming and
the western Dakotas

Concerning...Severe potential...Watch unlikely 

Valid 222024Z - 222230Z

Probability of Watch Issuance...20 percent

SUMMARY...Thunderstorms overspreading the region through 6 PM MDT
may not become particularly organized, but could still continue to
produce a few strong to locally severe surface gusts.

DISCUSSION...Thunderstorm activity has become increasingly
widespread within lee surface troughing across the higher plains, as
well as across the Black Hills vicinity, within/above a hot and
deeply-mixed boundary-layer that appears characterized by CAPE on
the order of 500-1000 J/kg.  This appears to be aided by forcing for
ascent associated with a weak impulse progressing through the mean
mid/upper ridging, which likely will be maintained across the region
into this evening.  Within this regime westerly deep-layer mean flow
and shear appear on the order of a generally modest 20-30 kt, which,
coupled with the weak CAPE, seem likely to limit the potential for
substantive organization.  Still, storms have already produced a few
observed strong surface gusts ranging from 39-47 kt, and this could
continue, with perhaps an isolated severe gust or two, as activity
develops eastward through 23-00Z.

..Kerr/Hart.. 07/22/2021

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

ATTN...WFO...BIS...UNR...BYZ...GGW...

LAT...LON   48140406 48210207 44080332 44150512 46250525 48140406 

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