MESOSCALE DISCUSSION 1917
   NWS STORM PREDICTION CENTER NORMAN OK
   0205 PM CDT TUE AUG 09 2011
   
   AREAS AFFECTED...CNTRL/SERN NY...SWRN NEW ENGLAND...CNTRL/ERN
   PA...NJ...NRN DEL
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 091905Z - 092000Z
   
   ALTHOUGH THE THREAT OF DMGG WINDS AND PERHAPS AN ISOLATED TORNADO
   MAY INCREASE THIS AFTERNOON...THE COVERAGE OF SEVERE STORMS REMAINS
   SOMEWHAT UNCERTAIN. A WW MAY BE PROPOSED RELATIVELY SOON.
   
   ACROSS PORTIONS OF THE UPPER MID ATLANTIC...A VORT MAX OVER CNTRL
   NY/PA AND BROADER ASCENT IN ASSOCIATION WITH A WEAK UPPER TROUGH
   CONTINUE TO SUPPORT A GENERAL WARM ADVECTION REGIME...WITH A SURFACE
   WARM FRONT CURRENTLY LOCATED ACROSS SRN NJ. LOW LEVEL CLOUD COVER IS
   REMAINING FIRM OVER MUCH OF THE AREA...THOUGH POCKETS OF CLEARING
   HAVE LED TO LOCALIZED DESTABILIZATION. RECENT VAD WIND PROFILE DATA
   OVER NJ IS STILL SHOWING SUFFICIENT LOW LEVEL HELICITY FOR STORM
   ROTATION...ESPECIALLY IN THE VICINITY OF THE WARM FRONT...WHERE
   STORMS CONTINUE TO TRAIN ACROSS SRN NJ LEADING TO HEAVY RAINFALL.
   DMGG WINDS AND PERHAPS A TORNADO REMAIN POSSIBLE ACROSS THE POPULOUS
   AREAS OF NRN DEL NWD INTO NYC/LONG ISLAND.
   
   MEANWHILE FARTHER W...A VORT MAX ACROSS WRN NY AND AN ADDITIONAL
   CONVECTIVELY INDUCED WEAK VORT MAX ACROSS THE OH VALLEY /ORIGINATING
   FROM YESTERDAYS CONVECTION IN THE UPPER MS VALLEY/ CONTINUE TO
   PROGRESS EWD...AND MAY INFLUENCE STRONGER STORMS LATER THIS
   AFTERNOON ACROSS CNTRL NY/PA...AND SERN NY/ERN PA. IN ADVANCE OF
   THESE SUBTLE UPPER FEATURES AND AN EWD PROGRESSING COLD FRONT...MORE
   WIDESPREAD CLEARING OF STRATUS HAS LED TO TEMPERATURE VALUES IN THE
   MID 60S TO NEAR 80 F...LEADING TO MARGINAL INSTABILITY. DEEP LAYER
   WINDS REMAIN STRONGEST IN A CORRIDOR FROM CNTRL NY/PA EWD...AND THE
   20Z OUTLOOK WILL LIKELY EXPAND THE SLIGHT RISK WWD. MULTICELLULAR
   CLUSTERS AND PERHAPS DISCRETE CELLS CAPABLE OF DMGG WIND AND/OR AN
   ISOLATED TORNADO WILL BE POSSIBLE.
   
   ..HURLBUT.. 08/09/2011
   
   
   ATTN...WFO...OKX...ALY...PHI...BGM...CTP...
   
   LAT...LON   42147344 40927298 40127398 39477473 39837614 39817789
               40577817 41997694 42497613 42347390 42147344