Mesoscale Discussion 1428
   NWS Storm Prediction Center Norman OK
   1154 PM CDT Fri Aug 06 2021

   Areas affected...Parts of southern/eastern South Dakota

   Concerning...Severe Thunderstorm Watch 411...

   Valid 070454Z - 070700Z

   The severe weather threat for Severe Thunderstorm Watch 411
   continues.

   SUMMARY...Strong wind gusts continue, but may gradually begin to
   wane with storms spreading north of Chamberlain, toward the Huron
   area, during the next few hours.  At least scattered strong new
   thunderstorms may   continue to develop near the Interstate 90
   corridor around Sioux Falls through 1-2 AM CDT.

   DISCUSSION...Strongest recent thunderstorm development has been
   focused in a small cluster near the nose of a north-northeastward
   surging rear inflow jet which spread across the Valentine NE/Winner
   SD area earlier this evening.  This has reached areas of south
   central South Dakota between Pierre and Chamberlain, where various
   wind sensors continue to indicate strong to severe surface gusts,
   but this may gradually wane as convection progresses into less
   unstable environment near/north of Huron by 06-07Z.

   Strongest boundary-layer instability, steepest lower/mid
   tropospheric lapse rates and strongest shear remain focused along a
   remnant baroclinic zone slowly shifting north of the eastern
   Nebraska /South Dakota border area.  With a nocturnally
   strengthening low-level jet focusing increasing lift associated with
   warm advection along this boundary, at least scattered vigorous new
   thunderstorm development may begin to initiate during the next few
   hours.

   ..Kerr.. 08/07/2021

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

   ATTN...WFO...FSD...ABR...

   LAT...LON   44869900 44829719 44049673 43589589 42949615 42819690
               43199820 43599835 44179897 44869900