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Winter Weather Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 2014Z Nov 18, 2017)
 
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Abbreviations and acronyms used in this product
 
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
314 PM EST SAT NOV 18 2017

VALID 00Z SUN NOV 19 2017 - 00Z WED NOV 22 2017


DAYS 1-3...

...PACIFIC NORTHWEST/NORTHERN ROCKIES...

HEAVY SNOWS ARE EXPECTED TO RETURN TO PORTIONS OF PACIFIC
NORTHWEST LATE SUN INTO EARLY MON AS A POSITIVELY-TILTED SHORTWAVE
TROUGH DROPS INTO THE REGION.  STRONG SOUTHWESTERLY INFLOW ALONG
THE ASSOCIATED FRONTAL BAND ALONG WITH ASCENT FORCED BY AN
APPROACHING JET STREAK ALOFT IS EXPECTED TO CONTRIBUTE TO HEAVY
ACCUMULATIONS ALONG THE NORTHERN CASCADES. THE SNOW SPREADS
SOUTHEAST SUN NIGHT INTO MON INTO THE RANGES OF ID/NORTHWEST MT AS
THE UPPER LEVEL JET MAXIMA MOVES INLAND FROM WA STATE ACROSS ID
AND MT. A HIGH RISK FOR ACCUMULATIONS OF A FOOT OR MORE EXISTS
ACROSS THE OROGRAPHICALLY FAVORED HIGHER PEAKS...WITH MANUAL
FORECASTS OF A COUPLE OF FEET OF SNOW IN PARTS OF THE NORTHERN WA
CASCADE HIGHER ELEVATIONS.  SNOW TAPERS ON TUE (DAY 3) AS THE
UPPER RIDGE DEVELOPING LEADS TO SNOW LEVELS RISING...LIMITING
POTENTIAL FOR ANY ADDITIONAL HEAVY SNOW.

...GREAT LAKES/NORTHEAST...

LOW PRESSURE IS FORECAST TO TRACK NORTHEAST ALONG THE ST LAWRENCE
VALLEY THROUGH SUNDAY BEFORE TURNING NORTH INTO LABRADOR MONDAY. 
WARM LOW LEVEL TEMPS WILL SUPPORT MOSTLY RAIN...HOWEVER THERE MAY
BE ENOUGH SHALLOW LOW LEVEL COLD AIR TO SUPPORT SOME FREEZING RAIN
AND MINOR ICE ACCUMULATIONS AT THE ONSET OF PRECIPITATION ACROSS
NORTHERN MAINE SUN MORNING BEFORE CHANGING OVER TO RAIN.  COLD AIR
ADVECTION ON THE BACKSIDE OF THE SYSTEM SUPPORTS SNOW SHOWERS
DEVELOPING ACROSS PORTIONS OF NORTHERN NY AND NEW ENGLAND.
STRONG WEST-NORTHWESTERLY FLOW IN THE WAKE OF THE SYSTEM...WITH
EMBEDDED SHORTWAVE ENERGY ALOFT...IS EXPECTED TO SUPPORT
LAKE-EFFECT SNOW SHOWERS...WITH SOME OF THE GUIDANCE SHOWING THE
POTENTIAL FOR SOME LOCALLY HEAVY ACCUMULATIONS SUN INTO EARLY MON
NEAR THE SOUTHEAST CORNER OF LAKE ONTARIO.  A FEW INCHES ARE ALSO
EXPECTED DOWNSTREAM OF LAKE ERIE...AND ALSO IN UPSLOPE AREAS OF
NORTHERN WV.

FOR DAYS 1-3...THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN
10 PERCENT.

PETERSEN