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MESOSCALE DISCUSSION 0026
NWS STORM PREDICTION CENTER NORMAN OK
0508 AM CST WED JAN 07 2009
AREAS AFFECTED...PARTS OF NE PA...NRN NJ...SE NY THRU MUCH OF SRN
NEW ENGLAND
CONCERNING...FREEZING RAIN
VALID 071108Z - 071415Z
STEADY MODERATE FREEZING RAIN IS EXPECTED TO DEVELOP ACROSS THE
REGION...LIKELY LEADING TO SIGNIFICANT ICING THIS MORNING.
A MID-LEVEL SHORT WAVE IMPULSE...EMANATING FROM THE BASE OF THE
LARGE-SCALE TROUGH OVER THE MISSISSIPPI VALLEY...IS NOW RAPIDLY
LIFTING NORTHEASTWARD THROUGH THE SOUTHERN/CENTRAL APPALACHIANS. AS
THIS MOTION CONTINUES...A STRONG DOWNSTREAM LOWER/MID TROPOSPHERIC
WARM ADVECTION REGIME APPEARS LIKELY TO BECOME FOCUSED IN A BELT
FROM THE LEE OF THE NORTH CENTRAL APPALACHIANS THROUGH THE LOWER
HUDSON VALLEY AND MUCH OF SOUTHERN NEW ENGLAND BY THE 13-15Z TIME
FRAME. WITHIN AN ALREADY SATURATED ENVIRONMENT...ASSOCIATED FORCING
FOR UPWARD VERTICAL MOTION IS EXPECTED TO INTENSIFY
PRECIPITATION...MUCH OF WHICH WILL BE IN THE FORM OF RAIN.
DESPITE CONTINUED DEEPENING OF THE PRIMARY SURFACE CYCLONE OVER THE
LOWER GREAT LAKES...A SECONDARY SURFACE LOW ALREADY APPEARS TO BE
DEVELOPING OFF NORTHERN MID ATLANTIC COASTAL AREAS. AND...
SUB-FREEZING BOUNDARY LAYER AIR SEEMS LIKELY TO REMAIN ENTRENCHED
ACROSS THE POCONOS...CATSKILLS...LOWER HUDSON VALLEY /MOSTLY
NORTHWEST THROUGH NORTH OF THE NEW YORK METROPOLITAN AREA/...AND
MUCH OF SOUTHERN NEW ENGLAND INLAND OF COASTAL AREAS. THIS PROBABLY
WILL ALLOW FOR A THICK COATING OF ICE ON THE ORDER OF 1/4 TO 1/2+ ON
MOST EXPOSED OBJECTS/SURFACES...AS RAIN RATES AVERAGE NEAR OR IN
EXCESS OF .10 INCH PER HOUR THROUGH MUCH OF THE MORNING HOURS.
WARMING ALOFT IS EXPECTED TO BECOME SUFFICIENT TO SUPPORT A
CHANGEOVER FROM A LIGHT WINTRY MIX TO LIGHT TO MODERATE FREEZING
RAIN NORTHWARD INTO AREAS NEAR/NORTH OF ALBANY...SOUTHERN VERMONT
AND NEW HAMPSHIRE BY 15-18Z.
..KERR.. 01/07/2009
...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...OKX...ALY...PHI...BGM...
LAT...LON 41707616 42367563 42737521 43137469 43067366 43167263
43367099 41877058 41367239 40667407 40777523 40937583
41407606 41707616
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