MESOSCALE DISCUSSION 1736
   NWS STORM PREDICTION CENTER NORMAN OK
   0205 PM CDT FRI JUL 31 2009
   
   AREAS AFFECTED...ERN PA...NJ...DE...NRN VA...CNTRL/ERN MD...CT AND
   SERN NY INCLUDING LONG ISLAND
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 644...
   
   VALID 311905Z - 312030Z
   
   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 644
   CONTINUES.
   
   A MESOSCALE LOW HAS FORMED OVER NCNTRL MD AND IS ASSOCD WITH A BOW
   ECHO THAT PRODUCED A MEASURED 74 MPH WIND GUST IN FREDERICK COUNTY
   MD AT 1807Z.  DISCRETE CELLS DEVELOPED RAPIDLY AHEAD OF THIS FEATURE
   WITH OCNL SUPERCELL CHARACTERISTICS.  STORMS HAVE BEEN STRUGGLING
   SOMEWHAT NORTH ALONG THE FRONT ACROSS SERN PA AND NWRN NJ WHERE DEEP
   CIRCULATION/CONVERGENCE WAS NOT AS STRONG.
   
   OBJECTIVE/MESOSCALE TRENDS SUGGEST THAT THE MOST UNSTABLE AIR MASS
   EXTENDS ENE FROM THE ERN MD STORMS INTO NRN/CNTRL DE TO CNTRL/SRN NJ
   WITH MLCAPE TO 2000 J/KG.  EXPECT THE MESOSCALE LOW WILL TRACK IN
   THAT DIRECTION WITH SLIGHTLY BACKED NEAR-SFC FLOW BECOMING
   COINCIDENT WITH A VEERING PROFILE IN THE 0.5-3 KM LAYER.  THIS WILL
   BOOST SRH AND SUPPORT A CONTINUED RISK FOR ISOLD BRIEF SUPERCELLS
   WITH RISK FOR A TORNADO OR TWO.  STORMS SHOULD TEND TO MOSTLY
   DEVELOP INTO BOWS GIVING LOCAL DMGG WIND GUSTS.  EXPECT THE SVR
   THREATS TO REACH WILMINGTON AND PHL METRO AREAS BEFORE 2030Z.
   
   ELSEWHERE...AT LEAST ISOLD SVR STORMS WITH DMGG WINDS CAN BE
   EXPECTED FARTHER NE INTO SRN NEW ENGLAND AND LONG ISLAND NY IN A
   COMPARATIVELY LESS UNSTABLE ENVIRONMENT.  HERE...THE ONLY NEGATIVE
   ELEMENT WILL TEND TO BE THE FACT THAT THE BOUNDARY LAYER DID NOT
   HEAT STRONGLY THIS AFTN.  NONETHELESS...SHEAR PROFILES WILL BE
   CONDUCIVE FOR AT LEAST ISOLD ORGANIZED STORMS WITH DMGG WINDS/BRIEF
   SPIN-UP.
   
   ..RACY.. 07/31/2009
   
   
   ATTN...WFO...BOX...OKX...ALY...PHI...AKQ...CTP...LWX...
   
   LAT...LON   38457815 41307458 41877304 41337196 40707240 40267394
               38727486 38747600 38007604 38457815