MESOSCALE DISCUSSION 2278
   NWS STORM PREDICTION CENTER NORMAN OK
   1201 PM CDT SAT OCT 29 2011
   
   AREAS AFFECTED...CNTRL AND ERN PA...NRN NJ...SERN NY...NRN CT...NRN
   RI...WRN AND CNTRL MA...SRN VT AND NH
   
   CONCERNING...HEAVY SNOW 
   
   VALID 291701Z - 292200Z
   
   BANDS OF MODERATE TO HEAVY SNOW WILL SHIFT ENEWD THROUGH PA...SERN
   NY AND SRN NEW ENGLAND DURING THE AFTERNOON. SNOWFALL RATES OF 1+
   INCH PER HOUR WILL REMAIN LIKELY IN THE HEAVIEST BANDS AND MIGHT
   OCCASIONALLY APPROACH 2 INCHES PER HOUR.
   
   EARLY THIS AFTERNOON...MODERATE TO HEAVY SNOW BAND HAS SET UP FROM
   CNTRL AND ERN PA ENEWD THROUGH NRN NJ AND SERN NY. SURFACE
   TEMPERATURES IN THIS REGION ARE AT OR A FEW DEGREES ABOVE FREEZING
   WITH WET BULB TEMPERATURES AROUND 32F. THE 12Z RAOBS AND RUC PFCS
   INDICATE SUB-FREEZING WET BULB TEMPERATURES JUST ABOVE THE SURFACE
   THROUGH THE REMAINDER OF THE TROPOSPHERE INLAND FROM THE COAST.
   HOWEVER...THE SURFACE WARM LAYER WILL LIKELY REMAIN DEEP ENOUGH TO
   KEEP THE PRECIPITATION RAIN IN MOST AREAS WITHIN ABOUT 30 SM OF THE
   COAST.
   
   THE SNOW IS DEVELOPING WITHIN A DEEP BAROCLINIC/FRONTOGENETIC ZONE
   THAT EXTENDS FROM THE MID ATLANTIC REGION NEWD THROUGH SRN NEW
   ENGLAND. WV IMAGERY SHOWS AN EXPANDING BAROCLINIC LEAF AND COOLING
   CLOUD TOPS OVER THE NERN STATES JUST DOWNSTREAM FROM A NEGATIVELY
   TILTED SHORTWAVE TROUGH AND ITS ASSOCIATED MID-LEVEL JET PIVOTING
   NEWD THROUGH THE MID ATLANTIC REGION. SURFACE LOW OFF THE MID
   ATLANTIC COAST WILL DEEPEN AND LIFT NWD TOWARD SRN NEW ENGLAND IN
   ASSOCIATION WITH UPPER DIVERGENCE ACCOMPANYING THE UPPER JET. IN THE
   PROCESS...FRONTOGENETIC FORCING AND ISENTROPIC ASCENT SHOULD
   INCREASE FROM ERN PA THROUGH SRN NEW ENGLAND DURING THE AFTERNOON.
   THIS ZONE OF ASCENT IS OCCURRING WITHIN THE PORTION OF THERMODYNAMIC
   PROFILE FAVORABLE FOR SNOW GROWTH. IN ADDITION...PFCS AND CROSS
   SECTION DATA INDICATE PRESENCE OF AT LEAST WEAK UPRIGHT AND
   SLANTWISE INSTABILITY SUGGESTING CONVECTIVE ENHANCEMENT ALSO REMAINS
   LIKELY. WET BULB TEMPERATURES IN THE NEAR SURFACE LAYER WILL REMAIN
   AT OR ABOVE FREEZING...PROMOTING A WETTER SNOW...AND THIS COULD
   REDUCE ACCUMULATION RATES SOMEWHAT DESPITE THE PRESENCE OF LARGE
   FLAKES.
   
   ..DIAL.. 10/29/2011
   
   
   ATTN...WFO...GYX...BOX...OKX...ALY...PHI...BGM...CTP...
   
   LAT...LON   42107162 41477315 40867422 40127569 40237758 41237755
               42527515 43187213 42827118 42107162