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Winter Weather Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 0836Z Nov 17, 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
336 AM EST FRI NOV 17 2017

VALID 12Z FRI NOV 17 2017 - 12Z MON NOV 20 2017


DAYS 1-3...

...CENTRAL ROCKIES...

UPPER FORCING ASSOCIATED WITH A POSITIVELY-TILTED TROUGH MOVING
ACROSS THE WESTERN U.S. ALONG WITH LOW TO MID LEVEL FRONTOGENESIS
WILL SUPPORT ADDITIONAL HEAVY SNOWS ACROSS PORTIONS OF THE CENTRAL
ROCKIES...WITH WPC DAY 1 PROBABILITIES INDICATING AT LEAST A
SLIGHT RISK FOR ACCUMULATIONS OF 8-INCHES OR MORE ACROSS THE
MOUNTAINS OF NORTHERN UTAH TO FAR SOUTHERN WYOMING...CENTRAL
COLORADO AND FAR NORTHERN NEW MEXICO.  THE HEAVIEST AMOUNTS ARE
EXPECTED TO FOCUS ACROSS CENTRAL COLORADO...WITH WPC PROBABILITIES
SHOWING A MODERATE TO HIGH RISK FOR ACCUMULATIONS OF A FOOT OR
MORE ACROSS THE ELK MOUNTAINS AND SAWATCH RANGE.  SNOWS ARE
EXPECTED TO DIMINISH BY SAT MORNING AS THE TROUGH SHIFTS EAST INTO
THE PLAINS...FOLLOWED BY AN UPPER RIDGE MOVES ACROSS THE WESTERN
U.S.

...PACIFIC NORTHWEST AND THE NORTHERN ROCKIES...

HEAVY SNOWS ARE EXPECTED TO RETURN TO THE REGION BY LATE SUN AS
THE AFOREMENTIONED RIDGE GIVES WAY TO ANOTHER POSITIVELY TILTED
UPPER TROUGH DROPPING SOUTHEAST INTO THE REGION.  HEAVY MOUNTAIN
SNOWS ARE POSSIBLE FROM THE OLYMPICS AND CASCADES TO PORTIONS OF
THE NORTHERN ROCKIES...WITH HEAVY AMOUNTS MOST LIKELY OVER THE
NORTHERN CASCADES WHERE WPC DAY 3 PROBABILITIES (ENDING 12 UTC
MON) ARE SHOWING A MODERATE RISK FOR ACCUMULATIONS OF A FOOT OR
MORE FOR AREAS ABOVE 3000 FT.

...GREAT LAKES TO THE NORTHEAST...

AS THE AFOREMENTIONED TROUGH TRAVERSING THE WESTERN U.S. ON FRI
MOVES INTO THE CENTRAL U.S. ON SAT...A SURFACE LOW IS FORECAST TO
DEVELOP OVER THE CENTRAL PLAINS AND TRACK TO THE NORTHEAST ACROSS
THE OH VALLEY.  WPC PREFERRED THE MORE NORTHERLY LOW TRACKS OF THE
GFS AND ECMWF...WHICH WOULD SUPPORT MOSTLY RAIN...WITH ONLY MINOR
SNOW ACCUMULATIONS ACROSS THE GREAT LAKES REGION ON SAT.  THE NAM
WITH ITS MORE SOUTHERLY LOW TRACK AND HEAVIER SNOW AMOUNTS ACROSS
THE OH VALLEY INTO THE NORTHEAST WAS LARGELY DISCOUNTED.  AS THE
LOW LIFTS INTO SOUTHERN QUEBEC ON SUN...STRONG WEST-NORTHWESTERLY
FLOW BEHIND THE TRAILING COLD FRONT WILL SUPPORT LAKE-EFFECT SNOW
SHOWERS...WHICH ARE EXPECTED TO SUPPORT AT LEAST SOME LIGHT
ACCUMULATIONS IN THE LEE OF THE LAKES.

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

PEREIRA