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Winter Weather Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 0808Z Nov 20, 2017)
 
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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
308 AM EST MON NOV 20 2017

VALID 12Z MON NOV 20 2017 - 12Z THU NOV 23 2017


DAYS 1-3...

...PACIFIC NORTHWEST/NORTHERN ROCKIES...

A SHORTWAVE TROUGH MOVING INTO THE PACIFIC NORTHWEST MON MORNING
WILL SPILL SOUTHEAST ACROSS THE TOP OF A BUILDING RIDGE...BRINGING
MOUNTAIN SNOWS WITH LOCALLY HEAVY ACCUMULATIONS TO PORTIONS OF THE
NORTHERN ROCKIES FROM CENTRAL IDAHO TO WESTERN MONTANA AND WESTERN
WYOMING MON INTO MON NIGHT.  THE UPPER RIDGE WILL CONTINUE TO
BUILD ACROSS THE WESTERN U.S. ON TUE...GREATLY LIMITING THE THREAT
FOR ANY WIDESPREAD HEAVY SNOWS.  HOWEVER...ENTRENCHED LOW LEVEL
COLD AIR MAY SUPPORT A PERIOD OF FREEZING RAIN WITH MINOR ICING
ACROSS SOME OF THE INTERIOR VALLEYS OF THE PACIFIC NORTHWEST ON
TUE...PARTICULARLY EAST OF THE CASCADES WHERE SEVERAL GUIDANCE
MEMBERS SHOW LOW LEVEL EASTERLY FLOW SUPPORTING A STRONG LOW LEVEL
INVERSION WITH SUBFREEZING SURFACE TEMPERATURES.  LITTLE TO NO
THREAT FOR WIDESPREAD HEAVY SNOWS IS FORECAST TO CONTINUE ACROSS
THE REGION THROUGH WED INTO EARLY THU AS THE UPPER RIDGE REMAINS
IN PLACE. 

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

PEREIRA