Quantitative Precipitation Forecast
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FOUS11 KWBC 220854
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
454 AM EDT SUN APR 22 2018

VALID 12Z SUN APR 22 2018 - 12Z WED APR 25 2018

DAYS 1-3...

...NORTHERN INTER-MOUNTAIN WEST TO NORTHERN HIGH PLAINS...

A WAVE RACING ALONG THE NORTHERN TIER OF THE COUNTRY TOWARD
CENTRAL CANADA WILL BE FOLLOWED BY ADDITIONAL DYNAMICS COMING IN
FROM THAT PACIFIC. THIS STREAM OF UPPER DYNAMICS WILL PUSH THROUGH
THE PAC NW, AMPLIFY AND SLIDE THROUGH THE INTER-MOUNTAIN WEST LATE
TONIGHT THROUGH MONDAY BEFORE EMERGING INTO THE HIGH PLAINS.

THIS SYSTEM WILL CAPITALIZE ON ENHANCED UPSLOPE FLOW FOR HEAVY
SNOW FROM SOUTHERN MT AND NORTHERN WY...INCLUDING THE NORTHERN
TETONS/ABSAROKA AND BIG HORN MTNS, ON MON AND ACROSS EASTERN WY
INTO WESTERN PORTIONS OF SD/NE INCLUDING THE BLACK HILLS ON TUES.

WPC FOLLOWED A BLEND OF THE ECMWF AND GFS THERMALS...WEIGHTED
SOMEWHAT MORE HEAVILY TOWARDS THE ECMWF...FOR HEAVY SNOW PROBS ON
MON BUT REVERTED TO A COMPROMISE OF THE GUIDANCE BY LATE TUESDAY.
THIS IS DUE TO CONTINUED SPREAD IN THE GUIDANCE WITH RESPECT TO
PROGRESSION OF THE SYSTEM ALOFT.  THIS CLEARLY HAS CONSEQUENCES ON
THE ADVANCEMENT OF SNOW SPREADING OUT INTO THE PLAINS.

THE PROBABILITY OF ICING GREATER THAN 0.25 INCHES IS LESS THAN 10
PERCENT ON EACH OF THE THREE DAYS.

BANN





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