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Mesoscale Discussion 211
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   Mesoscale Discussion 0211
   NWS Storm Prediction Center Norman OK
   1124 AM CST Sat Feb 25 2017

   Areas affected...Maryland...central and eastern Virginia and
   northern North Carolina

   Concerning...Severe potential...Watch possible 

   Valid 251724Z - 251930Z

   Probability of Watch Issuance...60 percent

   SUMMARY...Thunderstorms are expected to increase in coverage and
   intensity this afternoon ahead of a cold front. Locally damaging
   winds are possible, along with hail in the strongest cells. A watch
   may be needed if it is clear storms will become severe.

   DISCUSSION...Rapid surface heating continues across the region ahead
   of the cold front which extended from northwestern VA into western
   NC as of 17Z. Dewpoints were holding in the mid to upper 50s
   suggesting a well-mixed and unstable boundary layer with MUCAPE to
   around 1000 J/kg.

   Satellite and radar show a few weak thunderstorms already forming
   over the higher terrain near the front, and a general upward trend
   is expected through the afternoon as it progresses east. By 18-19Z,
   some storms may be severe. Wind profiles will continue to
   strengthen, especially in the mid to upper levels, with long
   hodographs favoring long-lived storms. Damaging winds appear to be
   the main threat with a broken line of cells or small bows. The cold
   air in the mid to upper levels would support the formation of hail.
   However, a relatively warm layer exists above 700 mb, and updrafts
   may struggle. As a result of this warm layer, storms may be slow to
   become severe, but with time, long-acting shear may overcome this,
   especially over eastern VA into MD, and northeastern NC later this
   afternoon.

   The tornado threat is low, but not zero. Although storms could
   remain cellular, and low-level shear is in the sufficient category
   with 0-1 SRH near 100 m2/s2, strong boundary layer mixing will be a
   detriment, as will be the warm layer aloft hampering vertical
   updraft accelerations in the lower parts of the storm.

   ..Jewell/Hart.. 02/25/2017


   ATTN...WFO...PHI...AKQ...CTP...LWX...RAH...RNK...

   LAT...LON   37997518 37457556 37037585 36707636 36497718 36377824
               36457905 36887910 37257891 37657868 38207835 38657805
               39117772 39627728 39737666 39627590 39267550 38877524
               38427508 37997518 

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Page last modified: February 25, 2017
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