SWOMCD
SPC MCD 131730
MAZ000-NHZ000-RIZ000-CTZ000-NYZ000-VTZ000-NJZ000-PAZ000-132130-
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
..PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
..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
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