Mesoscale Discussion 1604
   NWS Storm Prediction Center Norman OK
   0920 PM CDT Thu Aug 27 2020

   Areas affected...far southeast Montana into western South Dakota.

   Concerning...Severe Thunderstorm Watch 460...

   Valid 280220Z - 280345Z

   The severe weather threat for Severe Thunderstorm Watch 460
   continues.

   SUMMARY...Severe thunderstorms ongoing across portions of WW460 are
   expected to continue with a threat for damaging winds and large hail
   this evening. Upscale growth into an MCS appears probable with an
   increasing risk for damaging winds downstream where a new watch is
   likely later this evening.

   DISCUSSION...Several clusters of severe storms are currently ongoing
   across WW460 this evening. Recent reports of severe hail and wind
   gusts in excess of 70 mph signal continued organization of storms
   across South Dakota. The 00z UNR sounding shows an environment
   supportive of severe thunderstorms (including supercells) with 2000
   J/kg of MLCAPE and 55 kts of effective shear. 8.5-9 C/km mid-level
   lapse rates and supercell wind profiles suggest the threat for large
   to very large hail will likely continue for a few more hours, before
   upscale growth associated with the low-level jet and storm mergers
   shifts the threat toward damaging winds. A downstream watch is
   likely by 04z as cluster of storms is expected to organize into an
   MCS across southern South Dakota later this evening. 

   Across southern North Dakota, some hi-res guidance has shown an
   increase in convective coverage between 03-04z. Despite the
   increasing inhibition, 1000-1500 J/kg of MUCAPE would support some
   severe potential, primarily in the form of damaging winds and
   occasional severe hail, with any storm clusters that are able to
   organize.

   ..Lyons/Guyer.. 08/28/2020

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

   ATTN...WFO...FSD...ABR...BIS...UNR...BYZ...

   LAT...LON   46780338 46740196 46650085 45379886 44299848 43069917
               43060285 43760430 44780452 45620430 46780338