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Mesoscale Discussion 1211
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   Mesoscale Discussion 1211
   NWS Storm Prediction Center Norman OK
   1154 AM CDT Sat Jul 01 2017

   Areas affected...portions of central/eastern
   Pennslyvania...central/western Maryland...West Virginia
   Panhandle...and northern Virginia

   Concerning...Severe potential...Severe Thunderstorm Watch likely 

   Valid 011654Z - 011800Z

   Probability of Watch Issuance...80 percent

   SUMMARY...Thunderstorms are expected to increase in
   coverage/intensity this afternoon with a risk for damaging winds and
   perhaps large hail.  Trends will be monitored and a Severe
   Thunderstorm Watch is likely prior to 19Z.

   DISCUSSION...Thunderstorms have been slowly intensifying across
   portions of southern New York and western/central Pennsylvania in
   the vicinity of a surface trough of low pressure as of 1645Z. 
   Downstream, diurnal heating of a moist air mass with dew points in
   the lower 70s continues, and surface-based instability by early/mid
   afternoon should range between 1000-locally 2000 J/kg.  Increasing
   large-scale ascent will develop over the area this afternoon as a
   mid-level impulse moves northeast from the lower Great Lakes/Ohio
   Valley, contributing to a continued increase in thunderstorm
   coverage/intensity.  Deep-layer southwesterly shear of 30-40 kts
   will promote multicell clusters/line segments with a threat for
   damaging winds this afternoon.  Some potential exists for a
   supercell with mid-level rotation, especially with more discrete
   cells across the discussion area, resulting in the potential for
   isolated large hail.

   A Severe Thunderstorm Watch will likely be needed prior to 19Z for
   much of the area.

   ..Bunting/Grams.. 07/01/2017

   ...Please see for graphic product...


   LAT...LON   38627687 38517786 39027841 40007843 40897808 41297785
               41777767 42107751 42447692 42617647 42637624 42607598
               42347552 41527477 40867474 40117526 38627687 

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