SWOMCD
SPC MCD 200025
MAZ000-RIZ000-CTZ000-NYZ000-NJZ000-PAZ000-DEZ000-MDZ000-200530-
MESOSCALE DISCUSSION 2262
NWS STORM PREDICTION CENTER NORMAN OK
0625 PM CST SAT DEC 19 2009
AREAS AFFECTED...NJ...SERN PA...NRN DE...SRN NY...CT...RI...SRN MA
CONCERNING...HEAVY SNOW
VALID 200025Z - 200530Z
HEAVY SNOW WITH RATES OF 1 TO 2 IN/HR WILL PIVOT NEWD FROM THE
MID-ATLANTIC INTO SRN NEW ENGLAND THROUGH 06Z. THE MOST PERSISTENT
AREA OF HEAVY SNOW SHOULD LIE ACROSS PORTIONS OF THE NEW YORK CITY
METRO AREA...LONG ISLAND AND CT...WITH LOCALIZED RATES EXCEEDING 2
IN/HR AT TIMES. OCCASIONAL BLIZZARD CONDITIONS SHOULD COMMENCE
ACROSS THE ERN HALF OF LONG ISLAND AND SRN CT/RI/MA.
984 MB SURFACE CYCLONE CENTERED AROUND 150 SM E OF THE DELMARVA
PENINSULA HAS REMAINED NEARLY STEADY-STATE OVER THE PAST 12 HOURS.
NEVERTHELESS...AFTERNOON MODEL FORECASTS ARE CONSISTENT THAT
DEEPENING OF THIS LOW WILL OCCUR THROUGH THE 00-06Z PERIOD AS THE
MID-ATLANTIC SHORT WAVE TROUGH AMPLIFIES. THIS WILL LEAD TO
STRENGTHENING OF MID-LEVEL FRONTOGENESIS AND ISENTROPIC
ASCENT...COINCIDENT WITH THE DENDRITIC GROWTH LAYER...DEVELOPING
NEWD INTO SRN NEW ENGLAND. AS A RESULT...ONGOING MODERATE TO HEAVY
SNOW FALLING ALONG THE I-95 CORRIDOR FROM THE WASHINGTON D.C. TO NEW
YORK CITY METRO AREAS WILL PIVOT NEWD. PERSISTENT SNOWFALL RATES OF
1 TO 2 IN/HR WILL BE LIKELY FROM NJ NEWD INTO CT/RI THROUGH
06Z...WITH EMBEDDED BANDS SUPPORTING RATES BRIEFLY EXCEEDING 2
IN/HR.
AS THE OFFSHORE CYCLONE DEEPENS AND SLOWLY TRACKS NEWD...TIGHTENING
OF THE LOW-LEVEL PRESSURE GRADIENT WILL STRENGTHEN N/NELY SURFACE
FLOW. FREQUENT GUSTS AOA 35 MPH SHOULD REMAIN CONFINED TO THE ERN
PORTION OF LONG ISLAND INTO COASTAL CT/RI AND FAR SRN MA...SUPPORTED
BY 15Z SREF GUIDANCE. THIS SHOULD LEAD TO THE COMMENCEMENT OF
BLIZZARD CONDITIONS /ESPECIALLY TOWARDS 06Z/ AS HEAVIER SNOW
OVERSPREADS THIS REGION.
..GRAMS.. 12/20/2009
...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...BOX...OKX...ALY...PHI...
LAT...LON 41757040 41277122 40517312 40307364 38927489 39137558
39747596 40647533 41517433 42147307 42287187 42067084
41757040
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