Mesoscale Discussion 0856
   NWS Storm Prediction Center Norman OK
   0333 PM CDT Sat Jun 06 2020

   Areas affected...western South Dakota and western Nebraska

   Concerning...Severe potential...Watch likely 

   Valid 062033Z - 062230Z

   Probability of Watch Issuance...80 percent

   SUMMARY...Severe thunderstorm development seems probable in the next
   1 to 2 hours across portions of Nebraska and western south Dakota.
   Supercells may initially favor a large hail and tornado threat with
   eventual upscale growth and increasing damaging wind gust potential
   this evening.

   DISCUSSION...Breaks in mid-level cloud cover ahead of a negatively
   tilted upper low across the Rockies have allowed temperatures to
   warm into the 80s and 90s F across portions of western Nebraska and
   South Dakota. Strong surface advection of moisture continues thanks
   to a 996 mb lee low deepening over eastern Montana. Dewpoints in the
   mid 60s F are forecast to continue streaming northwestward and
   interacting with the increasingly warm airmass. Eroding inhibition,
   increasing MLCAPE of 1000-2000 J/kg, and convection increasing along
   the Front Range suggests convective initiation is probable in the
   next few hours along the thermal and moist axes. Regional VWPs show
   strong deep layer shear of 50-60 kt favoring an initial supercell
   mode. Steep mid-level lapse rates will support large hail (some
   significant) and damaging winds. The tornado threat is more
   uncertain given the propensity for storms to grow upscale rather
   quickly. However low-level SRH of 200-400 M2/s2 may support a
   tornado threat with any supercells that can remain discrete.

   ..Lyons/Thompson.. 06/06/2020

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

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

   LAT...LON   41000213 40970035 41200006 41540007 45740084 46030121
               46230184 46230329 46160384 45810412 45090416 43550417
               42020397 41280344 41070258 41000213