Mesoscale Discussion 1289
   NWS Storm Prediction Center Norman OK
   1216 PM CDT Mon Jul 20 2020

   Areas affected...much of South Dakota...and parts ouf southern North
   Dakota

   Concerning...Severe potential...Watch possible 

   Valid 201716Z - 201915Z

   Probability of Watch Issuance...60 percent

   SUMMARY...An anticipated increase in convective coverage/intensity
   expected over the next couple of hours suggests potential need for
   WW issuance by 2 PM.

   DISCUSSION...Latest surface analysis -- coupled visible satellite
   imagery -- indicates a weak surface boundary extending from
   southeastern South Dakota northwestward, to where it intersects a
   developing cluster of likely-still-elevated storms over northwestern
   South Dakota.  This convection appears to be occurring as the
   east-southeastward advance of a mid-level vort max/left exit region
   of a mid-level jet streak into the western Dakotas focuses ascent
   along the aforementioned surface boundary.  

   As daytime heating/destabilization continues across the area,
   capping indicated in morning soundings will continue to weaken,
   eventually allowing storms to become more surface-based, and also
   increase in coverage/intensity.  Aided by increasing
   west-northwesterly mid-level flow with the approach of the jet
   streak, atop low-level southeasterlies, shear will likewise help to
   bolster storm intensity.  Initial severe risk will likely remain
   primarily hail, with the more isolated/rotating storms.  However,
   some upscale growth into a somewhat more linear character could lead
   to increased wind potential as well.  We will continue to monitor
   evolution of the convection, with the expected increases in coverage
   requiring eventual consideration for WW issuance.

   ..Goss/Hart.. 07/20/2020

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

   ATTN...WFO...FGF...FSD...ABR...BIS...UNR...

   LAT...LON   45100216 45960070 46510017 46729929 46549805 45599683
               43399749 43650189 43970321 44680365 45100216