MESO: Mesoscale Discussion 2053

ACUS11 KWNS 020026
SWOMCD
SPC MCD 020026
MEZ000-020600-

MESOSCALE DISCUSSION 2053
NWS STORM PREDICTION CENTER NORMAN OK
0626 PM CST SUN DEC 01 2013

AREAS AFFECTED...PORTIONS OF MAINE

CONCERNING...WINTER MIXED PRECIPITATION

VALID 020026Z - 020600Z

SUMMARY...A NARROW...NE/SW-ORIENTED CORRIDOR EXTENDING THROUGH
PORTIONS OF INTERIOR SRN/ERN MAINE IS EXPECTED TO EXPERIENCE WINTER
MIXED PRECIPITATION THIS EVENING INTO THE OVERNIGHT HOURS.

DISCUSSION...REGIONAL WATER VAPOR IMAGERY INDICATES A PAIR OF WEAKLY
PHASED MID-LEVEL SHORTWAVE IMPULSES PROGRESSING ACROSS THE
INTERNATIONAL BORDER FROM NEW ENGLAND TO THE LOWER GREAT LAKES
REGION. MEANWHILE...A 1017-MB CYCLONE IS CURRENTLY ANALYZED S OF
BOSTON ALONG A NEAR-COASTAL FRONT THAT EXTENDS NEWD FROM THE CYCLONE
CENTER AND OFF THE COAST OF NEW ENGLAND. FORCING FOR ASCENT ON THE
COOL SIDE OF THE BOUNDARY ORIGINATING FROM MODEST ISENTROPIC ASCENT
WITHIN THE NRN QUADRANT OF THE CYCLONE WILL BE AUGMENTED BY
DCVA-INDUCED ASCENT PRECEDING THE IMPULSES. AS THE SFC LOW DEVELOPS
NEWD ALONG THE BOUNDARY THROUGH THE EVENING HOURS...PRECIPITATION
RATES WILL INCREASE FROM SW TO NE ACROSS THE MCD AREA.

THE OVERLAP OF THE STRONGER ASCENT WITH SUB-FREEZING SFC
TEMPERATURES WILL BE LIMITED IN SPATIAL EXTENT -- MAINLY CONFINED TO
A 25-50-MILE-WIDE CORRIDOR -- WHERE A MIX OF FREEZING
RAIN...SLEET...AND SNOW WILL BECOME INCREASINGLY LIKELY THROUGH THE
EVENING AND CONTINUE INTO THE OVERNIGHT HOURS. SNOW WILL BE THE MOST
LIKELY PRECIPITATION TYPE WITH GREATER DISPLACEMENT FROM THE
COAST...WITH A MIX OF SLEET AND FREEZING RAIN OF GREATER CONCERN
CLOSER TO THE COAST WHERE FORECAST SOUNDINGS SUGGEST A SHALLOW WARM
LAYER ALOFT CAPABLE OF AT LEAST PARTIALLY MELTING DESCENDING
HYDROMETEORS /AS OBSERVED AROUND 950 MB PER THE 00Z GYX RAOB/.

PRECIPITATION INTENSITY WILL GENERALLY BE MODEST...WITHOUT EVEN
STRONGER DEEP ASCENT PRESENT. HOWEVER...THE ASCENT SHOULD BE
SUFFICIENT TO SUPPORT AREAS OF FREEZING RAIN RATES REACHING AROUND
0.05 INCH PER 3 HOURS...WHILE SNOWFALL RATES COULD BRIEFLY/LOCALLY
REACH 1 INCH PER HOUR. THE HIGHEST OF THESE RATES WOULD BE MORE
LIKELY AFTER 04Z AS THE SPATIAL GAP BETWEEN THE CYCLONE AND THE
AFOREMENTIONED DCVA CLOSES TO SUPPORT SOME STRENGTHENING OF THE
LOW/MID-LEVEL ASCENT.

..COHEN/DARROW.. 12/02/2013

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

ATTN...WFO...CAR...GYX...

LAT...LON 44227051 44666976 45586828 45726768 45456740 45156746
44596882 44087003 43837080 44227051

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