Mesoscale Discussion 0993
   NWS Storm Prediction Center Norman OK
   0134 AM CDT Fri Jun 18 2021

   Areas affected...Far Southeast Minnesota...Far Northeast
   Iowa...South-central Wisconsin

   Concerning...Severe Thunderstorm Watch 278...

   Valid 180634Z - 180830Z

   The severe weather threat for Severe Thunderstorm Watch 278
   continues.

   SUMMARY...A threat for large hail and isolated wind damage will
   likely continue for a few more hours. The threat will probably be
   greatest across south-central Wisconsin where a cluster of strong
   thunderstorms is ongoing. The storms are expected to decrease in
   intensity as they move eastward toward Lake Michigan where
   instability is weaker.

   DISCUSSION...The latest surface analysis shows a 1004 mb low over
   far northeast Iowa with a quasi-stationary front extending eastward
   across south-central Wisconsin. An east-to-west line of strong to
   severe thunderstorms is ongoing near the front. The RAP is showing
   moderate instability across south-central Wisconsin with generally
   weaker instability with eastward extent. MUCAPE is estimated near
   2500 J/Kg in southwest Wisconsin and near 1000 J/kg in southeast
   Wisconsin. Effective shear is estimated near 50 kt across much of
   south-central Wisconsin which will likely support a severe threat
   for a few more hours. The instability, shear and steep mid-level
   lapse rates evident on forecast soundings, will be favorable for
   large hail with the stronger updrafts. Concerning the wind-damage
   potential, the RAP is showing CIN values in south-central Wisconsin
   in the -200 to -300 J/kg range. This will make it difficult for the
   stronger storms to produce wind damage. Any wind-damage potential
   should remain relatively isolated.

   ..Broyles.. 06/18/2021

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

   ATTN...WFO...MKX...ARX...

   LAT...LON   43918999 43859153 43519189 43079179 42929141 42948930
               42938769 43328741 43768786 43918999