Mesoscale Discussion 1494
   NWS Storm Prediction Center Norman OK
   0728 PM CDT Fri Aug 14 2020

   Areas affected...Upper Mississippi Valley

   Concerning...Severe Thunderstorm Watch 439...

   Valid 150028Z - 150200Z

   The severe weather threat for Severe Thunderstorm Watch 439
   continues.

   SUMMARY...Severe threat will shift slowly east this evening.

   DISCUSSION...Severe threat is shifting east across ww439. Frontal
   convection has grown upscale over the last few hours with a
   near-continuous squall line now evident from St. Louis County-arcing
   southwest into Brown County MN. This line is moving east at roughly
   30-35kt and will soon spread east of the MS River into western WI.
   However, air mass downstream over WI is notably more stable as the
   ongoing squall line is currently moving through the instability
   axis. Even so, large-scale forcing ahead of progressive short-wave
   trough should maintain this linear MCS as it translates east. The
   primary severe threat should become mostly wind due to the linear
   structure.

   ..Darrow.. 08/15/2020

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

   ATTN...WFO...DLH...ARX...MPX...

   LAT...LON   44469430 46349294 47619246 47369167 45429203 44109309
               44469430