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Mesoscale Discussion 954
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   Mesoscale Discussion 0954
   NWS Storm Prediction Center Norman OK
   0205 PM CDT Sun Jun 21 2020

   Areas affected...western South Dakota and other portions of the
   northern High Plains

   Concerning...Severe potential...Watch unlikely 

   Valid 211905Z - 212130Z

   Probability of Watch Issuance...20 percent

   SUMMARY...Scattered thunderstorms are expected to develop across
   western South Dakota and surrounding areas this afternoon. As these
   storms move southeast, damaging winds and large hail are possible.
   Given the likely marginal and isolated nature of the severe threat,
   a watch issuance is unlikely.

   DISCUSSION...West-northwest upper-level flow is overspread the
   northern Rockies and Plains with multiple low-amplitude shortwave
   troughs embedded within it per water vapor imagery. Sporadic
   lightning has been observed across portions of eastern Idaho and
   northern Wyoming this morning into early afternoon with a few
   observed lightning flashes in western South Dakota during the last
   hour with struggling convection. Given the moisture and forcing for
   ascent aloft, cloud cover has mitigated insolation across much of
   the northern high Plains/vicinity. This along with diffuse surface
   convergence have delayed and limited convective initiation. However,
   deeper cumulus clouds and higher cloud tops have been observed
   recently indicating potential destabilization. 

   As surface temperatures warm into the 70s to low 80s F storm
   coverage will likely increase. Storms are expected to develop during
   the afternoon and into the evening and move generally to the
   southeast across the area. The overall storm environment represents
   a marginally severe threat for large hail and damaging winds with
   coverage of severe storms likely relatively limited.

   ..Nauslar/Guyer.. 06/21/2020

   ...Please see for graphic product...


   LAT...LON   42150121 42760445 44790559 45470535 46490424 46320300
               45510075 44910012 43970021 42150121 

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