Mesoscale Discussion 0944
   NWS Storm Prediction Center Norman OK
   0317 PM CDT Sat Jun 20 2020

   Areas affected...southern South Dakota and western Nebraska

   Concerning...Severe potential...Watch possible 

   Valid 202017Z - 202215Z

   Probability of Watch Issuance...60 percent

   SUMMARY...Storms are beginning to develop across western/central
   South Dakota and western Nebraska. Storms are likely to intensify
   this afternoon/evening across the area with large hail and damaging
   winds as the main threats. A watch issuance is possible, although
   there is some uncertainty regarding severe storm coverage.

   DISCUSSION...A mid-level shortwave trough is rotating around the
   base of a larger, positively tilted upper-level trough over central
   Canada per water vapor imagery. Stronger winds and lower mid-level
   heights/temperatures are accompanying this feature as it moves
   southeast across eastern Montana and the western Dakotas. Enhanced
   surface convergence and upslope flow near the Black Hills has helped
   initiate thunderstorms across southwest South Dakota while
   convection is developing in central South Dakota along a surface
   trough. As storms move eastward they will encounter stronger
   instability/buoyancy with surface dewpoints of 55-60 F and MLCAPE of
   1000-2000 J/kg. As it the wave progresses and insolation continues,
   mid-level lapse rates will steepen and mid-level flow will
   strengthen increasing chances for severe storm development.

   Large hail and damaging winds are the main threats with these
   storms. Supercell development is possible with effective bulk shear
   of 25-40 knots, although it is likely convection will grow upscale
   by this evening. There is some uncertainty regarding severe storm
   coverage during the afternoon/evening, but severe hail/wind will be
   possible with any storm that develops across southern South Dakota
   and western Nebraska.

   ..Nauslar/Guyer.. 06/20/2020

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

   ATTN...WFO...FSD...ABR...GID...LBF...UNR...GLD...BOU...CYS...

   LAT...LON   44190291 44220131 43730086 43679952 42469918 40369925
               40380053 40290187 40880203 41950234 42770267 43330326
               43880333 44190291