Quantitative Precipitation Forecast
Issued by NWS

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FOUS11 KWBC 250927
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
526 AM EDT MON APR 25 2016

VALID 12Z MON APR 25 2016 - 12Z THU APR 28 2016

DAYS 1-3...

...CENTRAL GREAT BASIN TO THE CENTRAL/NORTHERN ROCKIES AND
ADJACENT HIGH PLAINS...

AN ACTIVE PATTERN ACROSS THE WESTERN U.S. WILL CONTINUE TO BRING
LATE SEASON SNOWFALL ACROSS THE HIGHER ELEVATIONS OF THE CENTRAL
GREAT BASIN AND CENTRAL/NORTHERN ROCKIES EARLY THIS WEEK.  THE
HEAVIEST AND MOST WIDESPREAD SNOW WILL BE WITH A LARGE SCALE UPPER
TROUGH AMPLIFYING INTO THE SOUTHWEST ON MONDAY...WHICH IS EXPECTED
TO EDGE TROUGH THE ROCKIES ON TUESDAY BEFORE PIVOTING OUT INTO THE
GREAT PLAINS ON WEDNESDAY.  STRONG LOW-MID LEVEL FORCING ALIGNING
OVER NORTHEAST NEVADA AND SOUTHWEST IDAHO SHOULD BRING PERIODS OF
HEAVY SNOW ALONG THE FAVORED TERRAIN EARLY MONDAY...BUT THEN THE
FOCUS FOR HEAVY SNOW WILL SHIFT EASTWARD INTO THE NORTHERN/CENTRAL
ROCKIES WHERE INCREASINGLY DIVERGENT FLOW ALOFT WILL COUPLE WITH
OROGRAPHICS/UPSLOPE FLOW LATE MONDAY INTO TUESDAY.  THE THREAT FOR
HEAVY SNOW SHOULD GRADUALLY DIMINISH ON WEDNESDAY WHILE THE UPPER
TROUGH LIFTS OUT INTO THE PLAINS AND THE ASSOCIATED SURFACE LOW
TRACKS TOWARDS THE MIDDLE MISSISSIPPI VALLEY.

THERE IS STILL A LOT OF UNCERTAINTY WITH THE EXACT
LOCATIONS/AMOUNTS OF SNOWFALL ACROSS THE CENTRAL GREAT BASIN AND
CENTRAL/NORTHERN ROCKIES SINCE MODELS HAVE YET TO LOCK IN ON THE
TIMING/AMPLITUDE DETAILS OF INDIVIDUAL SHORTWAVE IMPULSES EMBEDDED
IN THE LARGE SCALE TROUGH.  ALSO...MARGINAL THERMAL PROFILES ADD
TO THE FORECAST UNCERTAINTY WITH POSSIBLE ACCUMULATING SNOW ACROSS
THE NORTHERN/CENTRAL HIGH PLAINS.  TO ACCOUNT FOR THE LARGE AMOUNT
OF SPREAD IN MODEL GUIDANCE...THE WPC FORECAST STARTED WITH A
MULTI-MODEL BLEND.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.


...NORTHEAST...

HIGH PRESSURE HOLDING STRONG OVER THE NORTHEAST COULD ALLOW FOR
SNOW WITHIN THE NORTHERN EDGE OF WARM ADVECTION PRECIPITATION
DEVELOPING AHEAD OF SHORTWAVE ENERGY APPROACHING THE REGION MONDAY
NIGHT INTO TUESDAY.  THE WPC FORECAST STARTED WITH AN AGREEABLE
NAM/GFS/ECMWF...WHICH ALL SUGGESTED THE GREATEST CHANCE FOR ANY
ACCUMULATIONS SHOULD BE OVER THE ADIRONDACKS AND PORTIONS OF THE
GREEN AND WHITE MOUNTAINS.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.


GERHARDT

$$





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