Quantitative Precipitation Forecast
Issued by NWS

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FOUS11 KWBC 220915
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
515 AM EDT FRI APR 22 2016

VALID 12Z FRI APR 22 2016 - 12Z MON APR 25 2016


DAYS 1-3...

...CALIFORNIA/PACIFIC NORTHWEST/GREAT BASIN...

LATE SEASON SNOW WILL BE POSSIBLE ACROSS THE HIGHER ELEVATIONS OF
NORTHERN CALIFORNIA AND THE GREAT BASIN FRIDAY INTO SATURDAY AS A
DEEP UPPER LOW PROGRESSES INLAND OVER THE WESTERN U.S..  THE
HIGHEST ACCUMULATIONS SHOULD BE OVER THE SIERRA NEVADA...WHERE
LOWERING TEMPERATURES WITH THE APPROACHING HEIGHT FALLS...COMBINED
WITH STRONG WINDS BEHIND THE ASSOCIATED SURFACE FRONT...WILL BRING
MODERATE TO LOCALLY HEAVY SNOW TO THE FAVORED SLOPES OF THE
TERRAIN.  RIDGING SLIDING THROUGH ALOFT SHOULD BRIEFLY SUPPRESS
ACTIVITY ON SATURDAY..BUT THEN ADDITIONAL SNOW WILL BE POSSIBLE
WITH AN UPPER TROUGH AMPLIFYING OVER THE WESTERN U.S. SUNDAY INTO
MONDAY.  SNOW WITH THIS SECOND SYSTEM SHOULD BE MOSTLY LIGHT AND
FOCUSED IN THE HIGHER ELEVATIONS OF THE CASCADES AND CENTRAL GREAT
BASIN.

IN ORDER TO ACCOUNT FOR SOME OF THE MODEL SPREAD WITH THE EXACT
LOCATION AND AMOUNTS OF SNOWFALL ACROSS THE CASCADES AND CENTRAL
GREAT BASIN SUNDAY INTO MONDAY...A COMPROMISE OF THE GFS/ECMWF WAS
USED AS A STARTING POINT FOR THE WPC FORECAST.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.


DAYS 2-3...

...NORTHERN ROCKIES/ADJACENT HIGH PLAINS...

ACCUMULATING SNOW IS EXPECTED OVER THE HIGHER ELEVATIONS OF THE
NORTHERN ROCKIES AS THE CORE OF AN UPPER LOW CROSSES WYOMING ON
SATURDAY AND PROGRESSES INTO THE NORTHERN HIGH PLAINS ON SUNDAY.
THE HIGHEST SNOWFALL TOTALS SHOULD FOCUS ALONG THE RANGES OF
SOUTHWESTERN MONTANA AND NORTHWESTERN WYOMING...WHERE A SURFACE
LOW DEEPENING IN THE LEE OF THE ROCKIES WILL BRING MOIST LOW LEVEL
FLOW INTO THE TERRAIN AND FORCE PERIODS OF HEAVY UPSLOPE SNOW
ACROSS THE REGION.  DEPENDING ON HOW MUCH CONDITIONS COOL ON THE
BACK SIDE OF THE SYSTEM...AN AXIS OF ACCUMULATING SNOW COULD
SPREAD OUT INTO THE NORTHERN HIGH PLAINS AS THE SURFACE LOW TRACKS
TOWARDS THE MISSISSIPPI VALLEY SUNDAY NIGHT.

MODEL GUIDANCE CONTINUES TO SHOW A LARGE AMOUNT OF SPREAD AND
UNCERTAINTY WITH THE POTENTIAL FOR ACCUMULATING SNOW OVER THE
NORTHERN HIGH PLAINS SUNDAY NIGHT...SO A MULTI-MODEL BLEND WAS
USED AS A STARTING POINT FOR THE WPC FORECAST.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.


GERHARDT

$$





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