Quantitative Precipitation Forecast
Issued by NWS

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FOUS11 KWBC 202009
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
408 PM EDT FRI APR 20 2018

VALID 00Z SAT APR 21 2018 - 00Z TUE APR 24 2018

DAYS 1-3...

...CENTRAL ROCKIES...

A STRONG CLOSED MID TO UPPER LOW OVER THE FOUR CORNERS REGION IS
DELIVERING HEAVY SNOWFALL FOR THE CO TERRAIN THIS AFTERNOON. THIS
LARGE SCALE CIRCULATION WILL ADVANCE DOWNSTREAM AND ARRIVE INTO
THE CENTRAL TO SOUTHERN PLAINS ON SAT. THE GUIDANCE IS RATHER
UNANIMOUS IN A STEADY UPSLOPE COMPONENT REMAINING INTACT ACROSS CO
THAT SHOULD SUPPORT ADDITIONAL HEAVY SNOWFALL AMOUNTS. THE
UNCERTAINTY IN THE FORECAST IS WITH THERMALS AND WHETHER SNOWFALL
WILL SPREAD FROM THE CO ROCKIES OUT TO THE PALMER DIVIDE AND
CHEYENNE RIDGE. WPC TOOK A COMPROMISE OF THE ECMWF AND GFS FOR
PTYPE AND CARRIED MINIMAL SNOWFALL AMOUNTS.

...NORTHERN INTER-MOUNTAIN WEST...

AS A SHORT WAVE TROUGH MOVES THROUGH THE PAC NW TOWARD CENTRAL
CANADA, ADDITIONAL PAC DYNAMICS WILL REACH THE PAC NW, AMPLIFY AND
SLIDE THROUGH THE INTER-MOUNTAIN WEST LATE SUN THROUGH MON. THIS
SYSTEM WILL CAPITALIZE ON ENHANCED UPSLOPE FLOW FOR HEAVY SNOW
FROM CENTRAL ID THROUGH SOUTHERN MT INTO NORTHERN WY, WHICH
INCLUDES THE NORTHERN TETONS/ABSAROKA ND GIG HORN MTNS. WPC
FOLLOWED A BLEND OF THE ECMWF AND GFS THERMALS FOR HEAVY SNOW
PROBS.


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

MUSHER



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