Storm Prediction Center Mesoscale Discussion 862

   Mesoscale Discussion 0862
   NWS Storm Prediction Center Norman OK
   1059 PM CDT Mon May 20 2024

   Areas affected...parts of northeastern Colorado...northwestern
   Kansas...southwestern Nebraska

   Concerning...Tornado Watch 269...273...

   Valid 210359Z - 210600Z

   The severe weather threat for Tornado Watch 269, 273 continues.

   SUMMARY...Supercells will continue to pose a risk for large hail,
   locally damaging wind gusts and perhaps a tornado or two during the
   couple of hours, before storms evolve into a more organized cluster
   with potential for more widespread severe gusts perhaps occasionally
   in excess of 75 mph as early as Midnight-2 AM CDT.  Additional
   severe weather watches will likely be needed downstream later
   tonight.

   DISCUSSION...Several sustained discrete supercells have evolved in a
   developing cluster focused within strong warm advection centered
   around the 700 mb level.  This forcing is forecast to continue
   slowly developing eastward across the western Kansas/Nebraska border
   area through 05-07Z.  Moistening easterly low-level flow beneath
   this regime (including mid/upper 60s surface dew points advecting
   across and east of the McCook NE/Hill City KS vicinities) will
   continue to support increasingly unstable updraft inflow (including
   CAPE possibly in excess of 2000-3000 J/kg).  As this occurs,
   substantive further upscale growth and organization seems likely in
   the presence of strong deep-layer shear. 

   While storm motions are initially slow in the presence of modest
   southwesterly  deep-layer mean flow, which may have weakened some
   this evening, convective evolution during the next few hours
   probably will include the development of an increasingly
   well-defined mesoscale convective vortex.  Intensifying rear inflow
   to the south and southeast of this feature is expected to eventually
   contribute to a more rapid forward propagation and increasing
   potential for severe surface gusts.

   ..Kerr.. 05/21/2024

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

   ATTN...WFO...LBF...GLD...BOU...

   LAT...LON   40780197 40910110 40900053 39990031 39820136 39690196
               39450294 40160315 40780197