Storm Prediction Center Mesoscale Discussion 860

   Mesoscale Discussion 0860
   NWS Storm Prediction Center Norman OK
   0923 PM CDT Mon May 20 2024

   Areas affected...Northern Iowa and southern Minnesota

   Concerning...Severe Thunderstorm Watch 272...

   Valid 210223Z - 210400Z

   The severe weather threat for Severe Thunderstorm Watch 272
   continues.

   SUMMARY...Discrete supercells capable of producing large hail up to
   2.0 inches in diameter remain possible across northern IA this
   evening. Damaging wind gusts could also accompany collapsing
   thunderstorms.

   DISCUSSION...A couple of discrete, right moving supercells have
   evolved this evening over Cherokee, Clay, and Palo Alto Counties.
   Recent FSD VAD profiler data indicates deep layer shear magnitudes
   around 50 kt. Although slightly weaker shear is likely present
   further east and southeast, where ongoing supercells are persisting,
   the discrete nature of them along a nearly stationary boundary may
   be supporting localized storm pressure perturbations capable of
   significant updraft velocities. In addition, steep mid-level lapse
   rates/large CAPE within the hail growth zone (00Z OAX sounding) is
   also contributing larger hail potential. However, as MLCINH
   continues to increase updraft strength should slowly diminish and
   hail sizes should decrease. The severe threat will continue through
   the late evening hours along and just behind the surface front,
   where some elevated supercells will also be possible.

   ..Barnes.. 05/21/2024

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

   ATTN...WFO...ARX...MPX...DMX...FSD...

   LAT...LON   43289652 43379589 43559581 43569547 43909542 44249439
               44279275 44369242 44189199 43759173 43359190 43029245
               42879296 42809338 42609369 42419415 42279456 42149501
               42299640 42769660 43289652