Mesoscale Discussion 0710
   NWS Storm Prediction Center Norman OK
   0158 PM CDT Sun May 23 2021

   Areas affected...Parts of western South Dakota

   Concerning...Severe potential...Watch likely 

   Valid 231858Z - 232100Z

   Probability of Watch Issuance...80 percent

   SUMMARY...Thunderstorms will develop east through north-northeast of
   the Black Hills by 3-5 PM MDT, with the potential for a few to
   intensify and pose increasing risk for severe hail, and perhaps a
   couple of tornadoes.

   DISCUSSION...A surface frontal zone, associated with the
   southern/leading edge of shallow cold surface air, initially south
   through east-northeast of the Black Hills, is eroding from southeast
   to northwest.  There is variance between the NAM and Rapid Refresh
   concerning how this proceeds to the east and north-northeast of the
   Black Hills through the remainder of the afternoon, as surface
   pressures continue to fall  across the high plains in response to a
   couple of mid-level perturbations approaching the northern Rockies. 
   However, given potential for weak to moderate boundary-layer
   destabilization, in the presence of strong (and strengthening)
   deep-layer shear, the development of vigorous, organized convection
   appears possible by 21-23Z.  This may initially include supercells
   posing a risk for severe hail, along with a conditional risk for
   tornadoes.

   ..Kerr/Guyer.. 05/23/2021

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

   ATTN...WFO...ABR...UNR...

   LAT...LON   44320356 44950302 45580285 45850262 45690188 45010087
               43500197 43150271 43060333 44320356