Mesoscale Discussion 0715
   NWS Storm Prediction Center Norman OK
   0625 PM CDT Sun May 23 2021

   Areas affected...Western South Dakota...Southwestern North Dakota

   Concerning...Tornado Watch 197...

   Valid 232325Z - 240100Z

   The severe weather threat for Tornado Watch 197 continues.

   SUMMARY...Severe threat continues across all but the southwestern
   portions of ww197.

   DISCUSSION...Surface warm front is advancing slowly north across
   northwestern SD/southern ND early this evening. As a result,
   buoyancy is gradually increasing across extreme southern ND where
   surface temperatures have warmed into the lower 70s. One long-lived
   supercell that matured earlier across western SD has lifted to near
   Lemmon and will soon cross the warm front. This storm has produced a
   few tornadoes over southeastern Perkins County SD, and until it
   becomes elevated north of the warm front some tornado threat
   remains. Otherwise, an arcing band of organized convection has
   emerged from the northern Black Hills into northwestern NE. This
   activity should continue surging northeast across the remainder of
   southeastern/central portions of the watch, eventually spreading
   toward the ND border later this evening. Tornado threat remains
   highest with discrete supercells ahead of the squall line.

   There is some concern that low-level warm advection will begin to
   enhance the elevated convective threat north of the warm front over
   western ND over the next few hours. Forecast soundings suggest hail
   will be the biggest concern with this activity and some
   consideration is being given for a potential severe thunderstorm
   watch over this region.

   ..Darrow.. 05/23/2021

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

   ATTN...WFO...ABR...BIS...UNR...CYS...

   LAT...LON   43020461 46300361 46310023 43030147 43020461