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Winter Weather Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 0726Z Oct 28, 2014)
 
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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
326 AM EDT TUE OCT 28 2014

VALID 12Z TUE OCT 28 2014 - 12Z FRI OCT 31 2014


DAY 1...

...PACIFIC NORTHWEST...

THE PROBABILITY OF 4 INCHES OF SNOW IS CONFINED TO THE HIGHER
ELEVATIONS OF THE NORTHERN CASCADES OF WASHINGTON FOR DAY 1...WITH
A 3-WAY BLEND INVOLVING THE GFS/ECMWF/SREF MEAN PREFERRED FOR
LIQUID EQUIVALENT AMOUNTS AND THERMAL PROFILES AS THE SHORTWAVE
TROUGH CURRENTLY ENTERING THE PACIFIC NORTHWEST COAST MOVES INLAND
AND WEAKENS.  ELSEWHERE...THE PROBABILITY OF 4 INCHES OF SNOW IS
LESS THAN 10 PERCENT.

DAY 2...

THE PROBABILITY OF SIGNIFICANT SNOW AND ICE IS LESS THAN 10
PERCENT.

DAY 3...

THE PROBABILITY OF 4 INCHES OF SNOW IS BETWEEN 1 AND 10 PERCENT
ACROSS THE UPPER PENINSULA OF MICHIGAN AS WELL AS NORTHERN
MICHIGAN LATE DAY 3 AS LAKE ENHANCEMENT AND LAKE EFFECT
PRECIPITATION DEVELOP IN RESPONSE TO STEEPENING LOWER LEVEL LAPSE
RATES AND STRENGTHENING LOWER LEVEL WINDS CROSSING THE WARM WATERS
OF THE LAKES.  SEVERAL OF THE DETERMINISTIC SOLUTIONS...INCLUDING
THE NAM/GFS/ECMWF... SUPPORT BETWEEN 40 AND 70 PERCENT. 
HOWEVER...THE ENSEMBLE MEMBER SPREAD IS VERY HIGH...WITH THE 03Z
SREF MEAN SUGGESTING 1 INCH OR LESS AND THE ECMWF ENSEMBLE MEAN
AND GEFS MEAN LESS THAN 1 INCH.  FAVORABLE INFLUENCES OF THE LAKES
FOR PRECIPITATION ALMOST SEEMS CERTAIN.  HOWEVER...A LOT OF
VARIABLES FOR SNOW REMAIN TO BE RESOLVED...INCLUDED THE DETAILS OF
THE ASSOCIATED SHORTWAVE TROUGH OVER THE MORE DATA SPARSE REGION
OF NUNAVUT...ANY INTERACTIONS THIS TROUGH MAY HAVE WITH ANOTHER
TROUGH OVER BRITISH COLUMBIA...AS WELL AS SUFFICIENTLY COLD
BOUNDARY LAYER TEMPERATURES FOR PERSISTENT SNOWS CLOSE TO THE
LAKES.   

JAMES