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Mesoscale Discussion 1389
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   Mesoscale Discussion 1389
   NWS Storm Prediction Center Norman OK
   1034 PM CDT Fri Jul 21 2017

   Areas affected...Central/eastern ND...Northeast SD

   Concerning...Severe Thunderstorm Watch 428...

   Valid 220334Z - 220430Z

   The severe weather threat for Severe Thunderstorm Watch 428

   SUMMARY...Some severe thunderstorm threat will extend past the 04Z
   expiration time of WW 428. Local watch extension and/or new watch
   issuance may be required.

   DISCUSSION...Severe thunderstorms are ongoing across portions of ND
   and northern SD along and ahead of a cold front moving through the
   western Dakotas. This activity is being supported to some extent by
   a relatively strong vort max moving into southern MB, and strong
   convection is likely to continue into late tonight, particularly if
   any upscale growth can occur with one or more of the ongoing
   clusters of semi-discrete cells. 

   With the threat of large hail and damaging wind, and perhaps a brief
   tornado in the short term with ongoing discrete supercells,
   continuing past the 04Z expiration time of WW 428, local extension
   of the watch and/or new watch issuance is possible to cover the
   remaining threat. In addition, some severe threat is likely to
   extend into portions of northeast ND outside of WW 428, and new
   watch issuance is possible in that area.

   ..Dean/Guyer.. 07/22/2017

   ...Please see for graphic product...


   LAT...LON   44669817 44680050 46480151 48150119 48900041 48999851
               48979786 45939689 44629745 44669817 

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