Mesoscale Discussion 1602
   NWS Storm Prediction Center Norman OK
   0552 PM CDT Thu Aug 27 2020

   Areas affected...The western Dakotas into Wyoming and southeast
   Montana

   Concerning...Severe potential...Watch likely 

   Valid 272252Z - 280015Z

   Probability of Watch Issuance...95 percent

   SUMMARY...Severe storms, including supercells, are expected to
   develop and pose a risk for large to very large, hail damaging
   winds, and perhaps a tornado through this evening. A weather watch
   will likely be needed.

   DISCUSSION...Convection across the Bighorn Mountains of northeastern
   Wyoming has increased in coverage and intensity late this afternoon
   as lift from a shortwave trough has overspread the Rockies. Moist
   advection with southeasterly low level flow-will continue to
   increase dewpoints into the lower to middle 50s F this evening. This
   moisture and temperatures in the 80s and 90s is generating moderate
   to strong buoyancy with MLCAPE of 1500-3000 J/kg depicted by SPC
   mesoanaylsis. Erosion of the remaining inhibition is expected and
   additional storm development/organization appears likely by 00z. The
   wind field, as sampled by the 20z UNR sounding, is supportive of
   supercells initially with 40-50 kts of 6km shear. Steep mid-level
   lapse rates near 8.5 C/km will be very supportive of large to very
   large hail and damaging winds. A tornado or two is also possible
   given enhanced low-level veering near the stalled surface front and
   the initial supercellular mode. However, the tornado threat is much
   more uncertain given lingering residual cloud cover limiting
   destabilization and the resulting stronger inhibition over southern
   South Dakota. Eventual upscale growth into an organized MCS capable
   of significant damaging wind gusts is expected this evening with the
   increasing low-level jet. A weather watch will likely be needed in
   the next hour or two.

   ..Lyons/Guyer.. 08/27/2020

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

   ATTN...WFO...ABR...BIS...UNR...CYS...BYZ...GGW...

   LAT...LON   43180508 43940576 45880622 46890530 47080379 46800239
               46410176 44820159 43060258 42830384 43180508