MESOSCALE DISCUSSION 2161
   NWS STORM PREDICTION CENTER NORMAN OK
   0538 PM CDT SUN SEP 11 2011
   
   AREAS AFFECTED...S-CNTRL/SERN PA...SRN NJ...DE...MD...PARTS OF ERN
   WV...NRN VA...DISTRICT OF COLUMBIA
   
   CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 
   
   VALID 112238Z - 120015Z
   
   A FEW STORMS COULD POSE A SVR THREAT INTO EARLY EVENING.
   HOWEVER...THE ISOLATED NATURE OF THIS THREAT WILL PRECLUDE THE NEED
   FOR A WW.
   
   OROGRAPHIC INFLUENCES OVER THE CNTRL APPALACHIANS AND WEAK DCVA
   EMBEDDED IN A LONG FETCH OF SWLY FLOW ALOFT WILL CONTINUE TO SUPPORT
   SCATTERED THUNDERSTORMS INTO THE EARLY EVENING HOURS. LATE AFTERNOON
   MESOANALYSIS DEPICTS A DIFFUSE/STALLED SFC FRONT EXTENDING FROM
   CNTRL VA TO THE COAST NEAR THE VA/NC BORDER AND INTO THE OFFSHORE
   WATERS OF THE WRN ATLANTIC...COINCIDING WITH A NARROW CU BAND EAST
   OF 74W PER RECENT VISIBLE SATELLITE IMAGERY. NORTH OF THIS
   FEATURE...MODESTLY RICH BOUNDARY-LAYER MOISTURE -- SFC DEWPOINTS IN
   THE 60S TO LOWER 70S -- COMBINED WITH POCKETS OF INSOLATION ARE
   SUPPORTING MLCAPE VALUES FROM 500-1200 J/KG. THIS DEGREE OF
   INSTABILITY COULD PROMOTE OCCASIONALLY VIGOROUS/SUSTAINED
   UPDRAFTS...AUGMENTED BY 30-40 KT OF EFFECTIVE BULK SHEAR. WHILE
   MULTICELLULAR CLUSTERS COULD POSE A THREAT FOR MARGINALLY SVR
   HAIL/WIND ON AN ISOLATED BASIS...WEAK MID-LEVEL LAPSE RATES ALONG
   WITH THE ABSENCE OF STRONGER FORCING FOR ASCENT SHOULD SUBSTANTIALLY
   MITIGATE THE OVERALL SVR THREAT. STORMS ARE EXPECTED TO WEAKEN AFTER
   00Z AS DIABATIC COOLING COMMENCES.
   
   ..COHEN.. 09/11/2011
   
   
   ATTN...WFO...PHI...AKQ...CTP...LWX...PBZ...RLX...
   
   LAT...LON   40047894 40467742 40317521 39427466 38157513 37787579
               37887672 38257771 38227863 38327970 38858007 39437975
               40047894