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Mesoscale Discussion 1701
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   Mesoscale Discussion 1701
   NWS Storm Prediction Center Norman OK
   0133 PM CDT Thu Sep 17 2020

   Areas affected...Parts of northeastern South Carolina into southern
   North Carolina

   Concerning...Tornado Watch 492...

   Valid 171833Z - 172030Z

   The severe weather threat for Tornado Watch 492 continues.

   SUMMARY...Vigorous thunderstorms overspreading the northeastern
   South Carolina into southern North Carolina coastal plain will
   continue to pose a risk for tornadoes into early evening.  This
   includes the Florence SC area by 3-4 PM EDT, and at least some risk
   for a strong tornado.  A new tornado watch probably will be needed
   across parts of southern/eastern North Carolina within the next
   couple of hours.

   DISCUSSION...The remnant mid-level cyclonic vorticity center from
   Sally continues to migrate northeastward across the Carolina
   Piedmont.  Strongest convection has largely been focused near the
   intersection of the associated trailing mid/lower tropospheric wind
   shift and a warm frontal zone across the coastal plain.  This is now
   shifting east of the Sumter SC area and may increasingly impact
   areas near and south of Florence (where stronger 2-hourly surface
   pressure falls are now focused) through 19-20Z, before continuing
   into the coastal plain of southern North Carolina thereafter.

   Low-level shear remains maximized along the warm frontal zone near
   and just ahead of the vigorous convective cluster, near the nose of
   a 30-40 kt southerly 850 jet.  Although boundary-layer
   destabilization is still being inhibited, at least to some extent,
   along the warm frontal zone, embedded supercells with occasionally
   intensifying low-level mesocyclones will continue to pose a risk for
   the production of tornadoes into early evening.

   ..Kerr.. 09/17/2020

   ...Please see for graphic product...


   LAT...LON   34558001 35297836 35307762 34597779 33717939 33628025

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