MESOSCALE DISCUSSION 2121
   NWS STORM PREDICTION CENTER NORMAN OK
   1233 PM CDT SUN SEP 04 2011
   
   AREAS AFFECTED...PORTIONS OF NY AND PA
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 041733Z - 041900Z
   
   THE THREAT FOR SEVERE STORMS CAPABLE OF DAMAGING WINDS AND HAIL IS
   EXPECTED TO INCREASE THIS AFTERNOON AND CONVECTIVE TRENDS ARE BEING
   MONITORED FOR A POSSIBLE WATCH.
   
   THOUGH THE SYNOPTIC COLD FRONT REMAINS WEST OF REGIONAL...SURFACE
   ANALYSIS AND VISIBLE SATELLITE INDICATE A NUMBER OF WEAK WIND
   SHIFTS/OUTFLOW BOUNDARIES PRESENT ACROSS THE DISCUSSION AREA.  ONE
   OF WHICH APPEARS TO BE SUPPORTING THE DEEPENING OF CUMULUS ACROSS
   PARTS OF S-CNTRL NY /N AND E OF BGM/ INTO CNTRL PA /E OF UNV/. 
   HERE...BREAKS IN THE CLOUDS HAVE ALLOWED TEMPERATURES TO WARM INTO
   THE LOW-MID 80S...WHICH WHEN COUPLED WITH DEW POINTS IN THE UPPER
   70S-LOWER 80S IS RESULTING IN MLCAPE VALUES OF AROUND 2000 J/KG AND
   A WEAKENING CAP.
   
   CURRENT THINKING IS THAT LOW-LEVEL ASCENT ALONG EXISTING SURFACE
   BOUNDARIES AND GRADUAL INCREASE IN LARGE-SCALE FORCING AHEAD OF
   UPSTREAM TROUGH WILL FOSTER MULTIPLE BANDS/CLUSTERS OF TSTMS THIS
   AFTERNOON.  THE COMBINATION OF THE MODERATE INSTABILITY AND STEADILY
   STRENGTHENING DEEP-LAYER WIND FIELD WILL BE SUPPORTIVE OF ORGANIZED
   LINE SEGMENTS/BOWS CAPABLE OF DAMAGING WINDS AND HAIL.
   
   ..MEAD.. 09/04/2011
   
   
   ATTN...WFO...ALY...PHI...BGM...BUF...CTP...PBZ...
   
   LAT...LON   40407957 42657695 43987474 43407381 41917443 40587635
               39917736 39887898 40407957