Mesoscale Discussion 1258
   NWS Storm Prediction Center Norman OK
   0131 AM CDT Sat Jul 18 2020

   Areas affected...Eastern SD across southern/central MN to
   northwestern WI

   Concerning...Severe Thunderstorm Watch 381...

   Valid 180631Z - 180800Z

   The severe weather threat for Severe Thunderstorm Watch 381
   continues.

   SUMMARY...Southward development of the MCS should slow/diminish by
   08-09z along the west end of the convective line.  In the interim,
   the threat for damaging winds will continue.

   DISCUSSION...The large MCS with leading convective line and trailing
   rain area is aligned more west-east with westward extent into
   eastern SD.  Here, the gust front has propagated south of the
   primary convection, though strong/severe winds continue as evidenced
   by the gust to 66 kt at Watertown SD well ahead of the
   precipitation.  Southward development of the convection has exceeded
   almost all convection-allowing model forecasts since this evening,
   and this trend is likely to persist with storms moving into southern
   MN through about 09z.  As convective inhibition increases and the
   low-level jet veers from more southerly to more westerly through
   09z, lift atop the cold pool will become less efficient at
   initiating new storms, and southward development of the MCS will
   slow then cease from eastern SD into southwestern MN.  However, the
   threat for isolated strong/damaging winds will continue and may
   spread a little south of Severe Thunderstorm Watch 381 in eastern
   SD/southwestern MN, but an additional watch is probably not
   necessary across this area.

   Farther east, moisture advection along the moist axis, as well as
   weaker convective inhibition, will allow the MCS to persist through
   the morning across the watch area.  The damaging-wind threat will be
   greater with the more north-south oriented bowing segments and
   embedded mesovortices.

   ..Thompson.. 07/18/2020

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

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

   LAT...LON   44449741 44579611 44989448 45689270 46509179 46599125
               46239053 45839029 45539025 45019033 44679093 44219276
               44039439 43869587 43949681 44099742 44449741