Storm Prediction Center Mesoscale Discussion 821

   Mesoscale Discussion 0821
   NWS Storm Prediction Center Norman OK
   0616 PM CDT Thu May 21 2026

   Areas affected...parts of southwestern Nebraska...northeast and east
   central Colorado...adjacent northwestern Kansas

   Concerning...Severe Thunderstorm Watch 239...

   Valid 212316Z - 220115Z

   The severe weather threat for Severe Thunderstorm Watch 239
   continues.

   SUMMARY...Isolated to widely scattered supercell development is
   likely to persist through 6-8 PM MDT, accompanied by the risk for
   large hail and perhaps some increase in potential for a tornado near
   the Colorado/Kansas state border to the west-northwest of Goodland.

   DISCUSSION...Isolated thunderstorm development has undergone notable
   intensification the past few hours, aided by destabilization
   associated with continued boundary-layer warming and moistening. 
   This appears to have contributed to CAPE on the order of 1000-1500,
   in the presence of strong westerly deep-layer shear, though with
   mean ambient winds on the order of 20-30 kt, due to the veering of
   winds with height.

   Of the ongoing storms, the prominent supercell to the
   north-northeast of Limon CO appears to have the longest access to
   unstable inflow as it propagates eastward toward the Kansas state
   border to the west-northwest of Goodland through 7-8 PM MDT.  It
   appears that this may coincide with enlarging low-level hodographs
   accompanying strengthening east-southeasterly 850 mb flow, which may
   promote some further increase in potential for a tornado or two.

   ..Kerr.. 05/21/2026

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

   ATTN...WFO...GLD...BOU...CYS...

   LAT...LON   39890379 40800380 41420371 40840280 39750194 39040262
               39020312 39380365 39890379 

   MOST PROBABLE PEAK TORNADO INTENSITY...85-110 MPH
   MOST PROBABLE PEAK WIND GUST...55-70 MPH
   MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN