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Winter Weather Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 2047Z Mar 27, 2015)
 
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Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White


PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
447 PM EDT FRI MAR 27 2015

VALID 00Z SAT MAR 28 2015 - 00Z TUE MAR 31 2015


DAY 1...

...NORTHEAST...

A DEEP UPPER TROUGH WITH A STRONG DISTURBANCE MOVING NORTHEASTWARD
ALONG AND JUST OFF THE EAST COAST WILL DEVELOP A SIGNIFICANT
OFFSHORE CYCLONE BUT ALSO GENERATE WIDESPREAD INSTABILITY
RAIN/SNOWFALL WITH A POSSIBLE INVERTED TROUGH CONVERGENT BOUNDARY
ACROSS THE NORTHEAST.  THERE IS NO UNIFORM MODEL AGREEMENT BUT
THERE ARE CERTAINLY SIGNALS SUGGESTING THE POTENTIAL FOR MESOSCALE
SNOW DEVELOPMENT WITHIN THIS HIGHLY UNSTABLE/COLD AIRMASS.  AS
SUCH...THE BEST CHANCE FOR THIS TO DEVELOP IS FROM EASTERN LONG
ISLAND/CONNECTICUT ACROSS EASTERN NEW ENGLAND WITH ONLY A LOW
PROBABILITY FOR GREATER THAN 4 INCHES OF SNOW.  HOWEVER...LOCALLY
HEAVY SNOW IS POSSIBLE IN SMALL AREAS DIFFICULT TO PINPOINT. THE
OVERNIGHT ECMWF/ENSEMBLE MEANS CONTINUED TO DOWNPLAY THIS
POSSIBILITY ALTHOUGH THE MAJORITY OF THE OTHER OPERATIONAL
RUNS/ENSEMBLES THIS MORNING CONTINUED TO SUGGEST THE POSSIBILITY.
THE 12Z ECMWF DID INCREASE THE CHANCES FOR SNOW FROM THE EARLIER
RUN.

DAYS 1 TO 3...

...NORTHWEST/GREAT LAKES/NORTHEAST...

A STRONG SHORTWAVE/COLD FRONT WILL BRING AN END TO THE WARM
WEATHER OVER MONTANA ON SATURDAY WITH RAPIDLY DROPPING SNOW LEVELS
FROM 9000 TO ABOUT 5000 FEET WITH LOCALLY HEAVY SNOW IN THE
NORTHWESTERN CORNER OF THE STATE.  LOCAL ACCUMULATIONS OF 4 TO 8
INCHES ARE POSSIBLE IN THE HIGHEST PEAKS...AS WELL AS IN THE HIGH
PEAKS OF THE WASHINGTON CASCADES.

AS THE SYSTEM MOVES EASTWARD AND COMBINES WITH A SEPARATE TROUGH
MOVING SOUTHEASTWARD ACROSS SOUTH CENTRAL CANADA...LOW PRESSURE
WILL PASS NORTH OF THE GREAT LAKES ON DAY 2/SATURDAY EVENING INTO
SUNDAY WITH MOST OF THE SIGNIFICANT SNOW CONFINED TO NORTH OF THE
LAKES ACROSS ONTARIO...HOWEVER...THERE MAY BE SOME LIGHT FREEZING
RAIN FROM EASTERN MINNESOTA ACROSS WESTERN WISCONSIN...WHILE SNOW
DEVELOPS LATER ACROSS PORTIONS OF THE UPPER AND NORTHERN LOWER
SECTIONS OF MICHIGAN.  MOST OF THE ACCUMULATIONS WILL BE OF THE 1
TO 3 INCH VARIETY WITH A SMALL PROBABILITY OF GREATER THAN 4
INCHES OVER THE EXTREME NORTH.

BY DAY 3/SUNDAY EVENING INTO MONDAY...LOW PRESSURE CONTINUES
EASTWARD ACROSS SOUTHERN CANADA WITH SOME LIGHT SNOW STILL
POSSIBLE ACROSS PORTIONS OF NORTHERN AND WESTERN NEW YORK/NW
PENNSYLVANIA AND NORTHERN NEW ENGLAND. THERE IS STILL NO MORE THAN
A VERY LOW CHANCE OF SNOW ACCUMULATIONS GREATER THAN 4 INCHES. 

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT FOR
THE ENTIRE PERIOD.

KOCIN