MESO: Mesoscale Discussion 0040

ACUS11 KWNS 210531
SWOMCD
SPC MCD 210530
MAZ000-RIZ000-CTZ000-NYZ000-NJZ000-PAZ000-211030-

MESOSCALE DISCUSSION 0040
NWS STORM PREDICTION CENTER NORMAN OK
1130 PM CST THU JAN 20 2011

AREAS AFFECTED...PORTIONS OF THE NORTHEAST AND SRN NEW ENGLAND

CONCERNING...HEAVY SNOW

VALID 210530Z - 211030Z

BANDS OF MODERATE TO HEAVY SNOW WILL DEVELOP OVERNIGHT ALONG THE
I-84/95 CORRIDORS FROM ERN PA INTO MA. SNOWFALL RATES FROM 1 TO 2
IN/HR SHOULD OCCUR...MOST LIKELY ACROSS PORTIONS OF SRN NEW ENGLAND
AROUND OR JUST AFTER 12Z. ALTHOUGH DURATION OF HEAVY SNOW RATES IN
ANY ONE LOCATION SHOULD REMAIN RELATIVELY SHORT...HIGH TRAVEL IMPACT
ON MORNING RUSH HOUR APPEARS PROBABLE FROM THE NEW YORK CITY TO
BOSTON METRO AREAS.

05Z SURFACE ANALYSIS PLACED A 1004 MB CYCLONE OVER S-CNTRL PA WITH A
QUASI-STATIONARY/WARM FRONT DRAPED EWD TO LONG ISLAND. 00Z MODELS
ARE HIGHLY CONSISTENT WITH THE AMPLIFICATION OF AN UPPER-LEVEL SHORT
WAVE TROUGH /CURRENTLY CROSSING THE ERN GREAT LAKES AND UPPER OH
VALLEY/...RESULTING IN DEEPENING OF THE SURFACE LOW OFF THE NJ/LONG
ISLAND COAST THROUGH 12Z. STRENGTHENING LOWER-LEVEL WAA/ISENTROPIC
LIFT IN CONJUNCTION WITH MID-LEVEL DCVA WILL RESULT IN ROBUST FORCED
ASCENT DEVELOPING FROM ERN PA TO MA. THIS SUPPORTS THE AXIS OF
HIGHEST QPF/QSF DEPICTED IN THE LATEST SREF MEAN...GFS...HRRR...AND
ETA-KF CONTROL RUN OF THE SREF. SNOWFALL RATES WITHIN THIS AXIS
SHOULD REACH 1 IN/HR...WITH RATES NEAR 2 IN/HR INTO PORTIONS OF SRN
NEW ENGLAND TOWARDS 11-14Z.

THE 00Z NAM IS NOT QUITE AS ROBUST WITH INLAND QPF THAN IN PREVIOUS
RUNS WITH GREATER OFFSHORE RAINFALL DEVELOPMENT. IF THIS
OCCURS...SNOWFALL RATES AOA 1 IN/HR MAY BE RESTRICTED TO SRN NEW
ENGLAND WITH MORE MODERATE RATES WWD. HOWEVER...BASED ON RECENT IR
CLOUD-TOP COOLING AND INCREASING RADAR REFLECTIVITY FROM CNTRL MD
INTO ERN PA...SUSPECT THE NAM MAY BE AN OUTLIER WITH RESPECT TO A
PROBABLE BURST OF HEAVY SNOW OVER ERN PA/NRN NJ/SERN NY BETWEEN
07-11Z.

..GRAMS.. 01/21/2011

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...BOX...OKX...ALY...PHI...BGM...

LAT...LON 40397500 40577575 41157576 42057489 42557335 42687158
42687080 41947056 41497083 41247192 40817314 40457442
40397500

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