SWOMCD
SPC MCD 191727
NYZ000-CTZ000-NJZ000-PAZ000-DEZ000-MDZ000-VAZ000-DCZ000-WVZ000-192330-
MESOSCALE DISCUSSION 2261
NWS STORM PREDICTION CENTER NORMAN OK
1127 AM CST SAT DEC 19 2009
AREAS AFFECTED...VA...WV...MD...DE...NJ...PA...NY...CT
CONCERNING...BLIZZARD
VALID 191727Z - 192330Z
HEAVY SNOWFALL RATES OF 1-3 INCHES PER HOUR ARE LIKELY FROM THE D.C.
I-95 CORRIDOR NNEWD TOWARDS LONG ISLAND THIS AFTERNOON. WITHIN THIS
ZONE...BLIZZARD-LIKE CONDITIONS WILL LIKELY AFFECT PORTIONS OF THE
MEGALOPOLIS.
CENTER OF MAJOR EAST COAST CYCLONE/BOMB WILL MAKE GRADUAL NNEWD
PROGRESS FROM EAST OF VA CAPES TO SOUTHEAST OF CAPE MAY NJ THROUGH
EVENING WHILE UNDERGOING SUBSTANTIAL DEEPENING. STRONGEST
ASCENT...AND GREATEST HOURLY SNOWFALL RATES...WILL COINCIDE WITH
MOST INTENSE 850-700MB FRONTOGENESIS AND DEEPEST DENDRITE GROWTH
LAYER. LATEST NCEP-SREF GUIDANCE THROUGH 00Z SHOWS THESE DYNAMIC
AND THERMODYNAMIC FEATURES WILL TRANSITION ONLY SLOWLY NWD/NWWD
THROUGH LATE TODAY. BROAD AND QUASI-BANDED HEAVY SNOW FIELD SHOULD
GRADUALLY DECAY ON ITS SWRN FLANK...AND DEVELOP/INTENSIFY AND PIVOT
COUNTERCLOCKWISE FROM NRN MD/SERN PA TO SOUTH SHORE OF LONG ISLAND
THROUGH LATER THIS AFTERNOON.
SREF PROBABILITY MATCHED-MEAN /PMM/ 3-HOUR SNOWFALL TOTALS WERE USED
TO ARRIVE AT THE 1-2 INCH AND 2 INCH PLUS PER HOUR RATES DEPICTED IN
THE MD GRAPHIC. FURTHERMORE...AS BOMBOGENESIS OCCURS OFFSHORE...THE
INCREASING PRESSURE GRADIENT WILL LEAD TO STRONG WINDS AOA 35 MPH
FROM DELMARVA NWD TOWARDS LONG ISLAND. THIS IS SUPPORTED BY THE 00Z
NSSL 4 KM WRF SHOWING MAX 1 HOURLY WINDS BETWEEN 30-40 KTS OVER THIS
CORRIDOR. THUS...CONSIDERABLE FALLING...BLOWING...AND DRIFTING SNOW
WILL RESULT IN BLIZZARD CONDITIONS WITH VISIBILITIES NEAR ZERO IN
THE HEAVIEST SNOW BURSTS.
..SMITH/CARBIN.. 12/19/2009
...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...OKX...PHI...BGM...AKQ...CTP...LWX...
LAT...LON 39127892 40467719 40917595 41227425 41117293 40697292
39697441 38617598 38537640 38207695 38337796 39127892
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