MESOSCALE DISCUSSION 0543
   NWS STORM PREDICTION CENTER NORMAN OK
   0612 PM CDT FRI APR 19 2013
   
   AREAS AFFECTED...SERN NY...NJ...SERN PA...DE
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 192312Z - 200045Z
   
   PROBABILITY OF WATCH ISSUANCE...60 PERCENT
   
   SUMMARY...THE AREA IS BEING MONITORED FOR INCREASING SVR
   POTENTIAL...AND THE ISSUANCE OF A WW IS POSSIBLE.
   
   DISCUSSION...A N/S-ORIENTED SQUALL LINE EXTENDING FROM S-CNTRL NY
   INTO THE MID-ATLANTIC IS ADVANCING EWD AROUND 30 KT...AND FORECAST
   TO EXIT UPSTREAM TORNADO WATCHES IN THE 00Z-01Z TIME FRAME. ONLY
   MEAGER INSTABILITY EXISTS DOWNSTREAM OF THIS ACTIVITY...THOUGH THE
   STRENGTH OF THE ASCENT AT THE LEADING EDGE OF THE COLD POOL COMBINED
   WITH INTENSE LOW-LEVEL AND DEEP SHEAR WILL MAINTAIN A THREAT FOR
   ORGANIZED SVR STORMS WITH EMBEDDED LEWP/BOWING STRUCTURES INTO THE
   EVENING HOURS. DMGG WIND GUSTS AND PERHAPS A SPIN UP OR TWO MAY
   OCCUR...AND THIS MAY REQUIRE WW ISSUANCE. HOWEVER...THERE IS SOME
   POTENTIAL FOR UPSTREAM ACTIVITY TO DECREASE IN INTENSITY AS
   NOCTURNAL COOLING YIELDS DECREASING INSTABILITY...WHICH COULD
   MITIGATE THE SVR THREAT AND NEED FOR A WW.
   
   ..COHEN/THOMPSON.. 04/19/2013
   
   
   ATTN...WFO...OKX...ALY...PHI...BGM...
   
   LAT...LON   39307573 39827559 41227483 41787443 41827393 41547364
               40707382 39807419 38827491 38537518 38637561 39307573