Mesoscale Discussion 1675
   NWS Storm Prediction Center Norman OK
   0753 PM CDT Sat Sep 05 2020

   Areas affected...Southern MN...Northern/Eastern IA

   Concerning...Severe potential...Watch likely 

   Valid 060053Z - 060300Z

   Probability of Watch Issuance...80 percent

   SUMMARY...Deep convection will develop across southern Minnesota
   over the next few hours. Large hail is likely with the strongest
   storms. Severe thunderstorm watch will likely be issued by 03z.

   DISCUSSION...Early-evening water-vapor imagery clearly depicts a
   mid-level vorticity max over southeast SK, now digging southeast
   after topping the western US Ridge. This short-wave trough will
   provide large-scale background support for organized convection
   later this evening.

   00z soundings from MPX and ABR were quite dry this evening with
   meager buoyancy, but strongly sheared. However, OAX exhibited 1.3
   inch PW with a 14C 850mb dew point. 20kt southwesterly 850mb wind
   should increase into southern MN by 04z as LLJ strengthens to near
   40kt in response to the approaching short wave. Substantial moisture
   advection will be both necessary and likely over the next few hours
   before elevated convection materializes. While it's not entirely
   clear when elevated convection will develop, latest thinking is
   thunderstorms will likely develop quickly as moisture rushes
   northeast ahead of the digging mid-level speed max, possibly as
   early as 03z. Steep lapse rates and long, straight hodographs favor
   large hail.

   ..Darrow/Hart.. 09/06/2020

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

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

   LAT...LON   45659540 44799281 42719065 41739220 44279655 45659540