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Mesoscale Discussion 1312
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   Mesoscale Discussion 1312
   NWS Storm Prediction Center Norman OK
   0323 PM CDT Fri Jul 14 2017

   Areas affected...Southern Pennsylvania...Southern New
   Jersey...Delaware...Maryland...and northern Virginia

   Concerning...Severe Thunderstorm Watch 414...

   Valid 142023Z - 142130Z

   The severe weather threat for Severe Thunderstorm Watch 414

   SUMMARY...The severe threat continues across WW 414.

   DISCUSSION...Storms have evolved into a couple of extensive,
   southeastward-moving linear segments over the past couple of hours. 
   These storms have a history of occasional damaging wind gusts and
   isolated large hail.  A few supercellular structures have been noted
   recently especially in southern New Jersey as updrafts interact with
   a nearly stationary surface boundary across that region.  An
   isolated tornado cannot be completely ruled out here (in addition to
   a few instances of large hail), although the primary threat should
   be damaging wind gusts into the evening as storms migrate into a
   moderately unstable pre-convective airmass.

   North of the linear structures, recent convective overturning has
   stabilized localized areas (especially in southeastern Pennsylvania)
   and temporarily reduced the severe threat.  However, weak warm
   advection, pockets of insolation, and an approaching shortwave
   trough northwest of the region may support a renewed, yet isolated
   severe threat over the next few hours (especially into south-central

   ..Cook.. 07/14/2017

   ...Please see for graphic product...


   LAT...LON   40247917 40327758 40407599 40327478 40127410 39497381
               38807416 38277469 37997558 37957674 37977785 38087870
               38197926 38467960 38997970 39577949 40247917 

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