Mesoscale Discussion 1539
   NWS Storm Prediction Center Norman OK
   0502 PM CDT Fri Aug 21 2020

   Areas affected...Parts of northeastern South Dakota into
   southwestern Minnesota

   Concerning...Severe potential...Watch unlikely 

   Valid 212202Z - 212300Z

   Probability of Watch Issuance...20 percent

   SUMMARY...At least isolated strong to severe thunderstorm
   development probably will continue into early evening, with at least
   some potential to evolve into an organizing cluster accompanied by
   increasing risk for potentially damaging wind gusts.

   DISCUSSION...The mid-latitude westerlies appear to be undergoing at
   least some amplification.  This includes a digging short wave trough
   across the Saskatchewan/Manitoba/North Dakota vicinity.  Near/just
   ahead of the base of this trough, a mesoscale convective vortex
   within west-northwesterly flow has become a focus for recent intense
   convective development, which seems likely to continue into this
   evening.  

   Low-level convergence has become locally enhanced within broad weak
   surface troughing across northeastern South Dakota, where it is
   intersected by an apparent weak low-level baroclinic zone extending
   southeastward into west central Minnesota.

   Even with pronounced veering of low through mid-level wind fields,
   deep-layer shear across this region appears relatively modest (at or
   below 30 kt).  However, with boundary-layer dew points around 70 F
   contributing to large mixed-layer CAPE (in excess of 3000 J/kg) in
   the presence of steep mid-level lapse rates, thermodynamic profiles
   are supportive of continuing intense thunderstorm development which
   could pose a risk for severe hail and locally strong surface gusts. 
   And, into the 00-02Z time frame, the environment may become at least
   marginally conducive to the evolution of an organizing convective
   cluster, as suggested by recent runs of the High-Resolution Rapid
   Refresh.

   ..Kerr/Edwards.. 08/21/2020

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

   ATTN...WFO...MPX...FGF...FSD...ABR...

   LAT...LON   45669757 45799620 45329489 44379514 44549687 45669757