MESOSCALE DISCUSSION 2216
   NWS STORM PREDICTION CENTER NORMAN OK
   1130 AM CST THU DEC 13 2007
   
   AREAS AFFECTED...CNTRL/ERN PA...CNTRL/SRN NY...NRN
   NJ...MA/CT/RI...SRN VT/NH
   
   CONCERNING...WINTER MIXED PRECIPITATION 
   
   VALID 131730Z - 132130Z
   
   MODERATE TO HEAVY SNOW WILL SPREAD EWD FROM CNTRL/SRN NY AND NERN PA
   ACROSS THE REST OF SRN NEW ENGLAND THIS AFTERNOON. SNOWFALL RATES OF
   1 TO 2 IN/HR WILL REMAIN LIKELY...WITH THE MOST PROBABLE HEAVY SNOW
   FALL AXIS RUNNING FROM SERN NY ACROSS MA/CT/RI THROUGH 00Z. FARTHER
   SW...LIGHT TO MODERATE FREEZING RAIN AND SLEET WILL CONTINUE ACROSS
   CNTRL/SRN PA INTO NRN NJ THROUGH EARLY AFTERNOON...WITH
   PRECIPITATION RAPIDLY DIMINISHING AFTER 21Z.
   
   THE COMBINATION OF FORCED ASCENT AHEAD OF A SHORT WAVE TROUGH /NOW
   OVER THE OH RIVER VALLEY PER WATER VAPOR IMAGERY/ AND STRONG
   LOW-LEVEL WARM THETA-E ADVECTION /PER ANALYZED 12Z UPPER AIR CHARTS
   AND RECENT VAD PROFILERS/...HAVE RESULTED IN A BROAD REGION OF
   MODERATE TO OCCASIONALLY HEAVY PRECIPITATION FROM THE UPPER OH RIVER
   VALLEY INTO THE NORTHEAST. ALTHOUGH THIS PROGRESSIVE SHORT WAVE IS
   EXPECTED TO GRADUALLY WEAKEN AS AN UPSTREAM TROUGH EVOLVES FROM THE
   UPPER MIDWEST...LOW/MID-LEVEL ISENTROPIC LIFT WILL REMAIN FAVORABLY
   STRONG ACROSS SRN NEW ENGLAND THROUGH 00Z...WHILE ASCENT QUICKLY
   DIMINISHES FARTHER TO THE SOUTH AND WEST. MORNING MODELS ALONG WITH
   00Z 4 KM WRF-NSSL/NMM GUIDANCE DEPICT EXCELLENT AGREEMENT WITH THE
   HEAVIEST FROZEN QPF AXIS FROM NERN PA/SERN NY ACROSS MUCH OF
   CT/RI/MA. FARTHER N OVER SRN VT/NH...A LARGER DENDRITIC GROWTH ZONE
   WILL COMPENSATE FOR MORE MODEST ASCENT...AND THIS SHOULD BE
   SUFFICIENT FOR OCCASIONAL SNOWFALL RATES AROUND 1 IN/HR.
   
   EXTRAPOLATION OF REGIONAL ACARS AND MODEL FORECAST SOUNDINGS SUGGEST
   ONLY AROUND A 50 KM NEWD SHIFT IN THE DELINEATION BETWEEN
   PREDOMINANT SNOW VERSUS SLEET/FREEZING RAIN. THE THERMODYNAMIC
   PROFILE SHOULD REMAIN AOB FREEZING TO THE N AND E OF POU OWING TO
   CLIMATOLOGICALLY FAVORED SURFACE RIDGE AXIS ACROSS SRN NEW ENGLAND
   AND EXPECTED CYCLOGENESIS OFF THE LONG ISLAND COAST. THIS WILL
   EFFECTIVELY MAINTAIN AN E/NELY COMPONENT TO THE NEAR-SURFACE FLOW
   ALLOWING HEAVY SNOW TO FALL.
   
   ..GRAMS.. 12/13/2007
   
   
   ...NOTICE...
   SPC WINTER WEATHER MESOSCALE DISCUSSIONS WILL BE ISSUED ON A
   SCHEDULED BASIS FROM DECEMBER 1 THROUGH FEBRUARY 28...FOUR
   TIMES A DAY...AROUND 00 UTC...06 UTC...12 UTC...AND 18 UTC
   FOR SIGNIFICANT SHORT RANGE WINTER WEATHER EVENTS.
   
   ATTN...WFO...GYX...BOX...BTV...OKX...ALY...PHI...BGM...BUF...CTP...PBZ...
   
   42987070 42006993 41597029 41417143 41127239 40777327
   40607426 40257500 40057664 40247834 40877910 41577924
   42447812 43217624 43367449 43417303 43217158