Quantitative Precipitation Forecast
Issued by NWS

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FOUS11 KWBC 220827
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
326 AM EST WED NOV 22 2017

VALID 12Z WED NOV 22 2017 - 12Z SAT NOV 25 2017


DAYS 1-3...

...PACIFIC NORTHWEST/NORTHERN ROCKIES...

WITH A STRONG UPPER RIDGE IN PLACE OVER THE WESTERN U.S....SNOW
LEVELS WILL REMAIN HIGH...WITH LITTLE TO NO THREAT FOR HEAVY SNOWS
EXPECTED AWAY FROM THE HIGHEST PEAKS OF THE NORTHERN CASCADES AND
ROCKIES THROUGH EARLY THU.  THEN A WELL-DEFINED SHORTWAVE TROUGH
IS FORECAST TO MOVE ONSHORE THU...SUPPRESSING THE RIDGE...DRIVING
A COLD FRONT THROUGH THE PACIFIC NORTHWEST INTO THE NORTHERN
ROCKIES...BRINGING SNOW LEVELS DOWN LATE THU INTO EARLY FRI.
HEAVIEST ACCUMULATIONS ARE FORECAST TO FALL ALONG THE NORTHERN
WASHINGTON CASCADES WHERE WPC DAY 2 PROBABILITIES (ENDING 12 UTC
FRI) SHOW A MODERATE RISK FOR ACCUMULATIONS OF 8-INCHES OR MORE
AND A SLIGHT RISK FOR ACCUMULATIONS OF A FOOT OR MORE FOR THE
WESTERN SLOPES ABOVE 4000 FT.  PRECIPITATION IS EXPECTED TO WANE
ON FRI AND SNOW LEVELS ARE FORECAST TO LIFT ONCE AGAIN AS THE
UPPER TROUGH PROGRESSES QUICKLY TO THE EAST...WITH THE RIDGE
QUICKLY REBUILDING IN ITS WAKE.

...NORTHERN MAINE...

LOW PRESSURE DEVELOPING OFF OF THE CAROLINA COAST WED MORNING IS
FORECAST TO TRACK TO THE NORTHEAST...INTERSECTING A COLD FRONT AS
IT MOVES SOUTH OF NEW ENGLAND TOWARD THE CANADIAN MARITIMES.  THIS
IS EXPECTED TO BRING A PERIOD OF RAIN CHANGING TO SNOW ACROSS
PORTIONS OF THE NORTHERN NEW ENGLAND AS PRECIPITATION ENDS ACROSS
THE REGION LATE WED.  WITH THE BETTER FORCING LIFTING OUT TO
NORTHEAST BEFORE THE DEEPER COLD AIR ARRIVES...HEAVY SNOW
ACCUMULATIONS ARE NOT LIKELY...WITH WPC DAY 1 PROBABILITIES
(ENDING 12 UTC THU) SHOWING ONLY A SLIGHT RISK FOR ACCUMULATIONS
OF 4-INCHES OR MORE ACROSS NORTHERN MAINE.

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

PEREIRA

$$





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