Quantitative Precipitation Forecast
Issued by NWS

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116
FOUS11 KWBC 202041
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
340 PM EST MON FEB 20 2017

VALID 00Z TUE FEB 21 2017 - 00Z FRI FEB 24 2017

DAYS 1 TO 3...

...RANGES OF THE PACIFIC NORTHWEST/CALIFORNIA/GREAT
BASIN/ROCKIES...

THE ONGOING ATMOSPHERIC RIVER EVENT IMPACTING NORTHERN CA IS
EXPECTED TO CONTINUE THROUGH THE OVERNIGHT HOURS INTO TUE...WITH
ADDITIONAL HEAVY SNOWS LIKELY FOR THE SIERRA.  DAY 1 TOTALS
(ENDING 00 UTC WED) ARE LIKELY TO EXCEED 1 FOOT AND MAY REACH 2
FEET OR MORE ACROSS SOME OF THE HIGHER PEAKS OF THE NORTHERN AND
CENTRAL SIERRA.  ALTHOUGH REMOVED FROM THE DEEPER
MOISTURE...LEFT-EXIT REGION UPPER JET DYNAMICS ARE EXPECTED TO
EXTEND THE HEAVY SNOW THREAT FURTHER TO THE NORTH AS WELL INTO THE
SOUTHERN CASCADES.  MEANWHILE...SHORTWAVE ENERGY LIFTING ALONG THE
LEADING EDGE OF THE BROADER SCALE TROUGH ALONG WITH RESIDUAL
MOISTURE SPILLING EAST WILL SUPPORT HEAVY SNOWS IN THE RANGES OF
CENTRAL AND EASTERN ID...AS WELL AS NORTHWESTERN WY.

BY TUE EVENING WITH THE LEADING SHORTWAVE EJECTING WELL INLAND AND
THE ASSOCIATED FRONTAL BOUNDARY DROPPING WELL TO THE SOUTH INTO
SOUTHERN CA...EXPECT A DIMINISHING THREAT FOR WIDESPREAD HEAVY
SNOWFALL ACROSS THE WEST.  HOWEVER...POST-FRONTAL ONSHORE FLOW AND
ADDITIONAL SHORTWAVES EJECTING INLAND WILL CONTINUE TO SUPPORT
SNOW SHOWERS WITH LOCALLY HEAVY AMOUNTS POSSIBLE ACROSS THE
PREVIOUSLY HIGHLIGHTED REGIONS.

EXPECT A GROWING THREAT FOR LOCALLY HEAVY MOUNTAIN SNOWS FURTHER
TO THE SOUTH AS WELL INTO NORTHERN UT AND CO AS A LOW TO MID-LEVEL
BAROCLINIC ZONE DROPS SOUTH INTO THE REGION ON WED.  FROM LATE WED
INTO EARLY THU...SNOWS ARE EXPECTED TO CONTINUE ACROSS THIS REGION
AND SPREAD EAST INTO THE CENTRAL HIGH PLAINS AS SOUTHWESTERLY FLOW
AMPLIFIES AHEAD OF A WELL-DEFINED SHORTWAVE DIVING ACROSS THE
GREAT BASIN INTO THE CENTRAL ROCKIES.

...NORTHERN PLAINS TO LAKE SUPERIOR...

AS THE LEADING SHORTWAVE EMANATING FROM THE WESTERN U.S. TROUGH
EJECTS NORTHEASTWARD INTO THE NORTHERN PLAINS AND UPPER
MIDWEST...A STRIPE OF LIGHT SNOWS CAN BE EXPECTED NORTH OF THE
ASSOCIATED SURFACE LOW AS IT TRACKS FROM THE NORTHERN PLAINS WED
MORNING TO THE UPPER GREAT LAKES BY EARLY THU.  WPC FORECASTS
DISCOUNTED THE SLOWER AND MORE AMPLIFIED NAM
SOLUTION...DOWNPLAYING ITS STRIPE OF HEAVIER AMOUNTS IN FAVOR OF A
SOLUTION MORE IN LINE WITH THE LIGHTER ECMWF AND GFS SOLUTIONS.

THE PROBABILITY OF 0.25 INCHES OF ICE IS LESS THAN 10 PERCENT DAYS
1-3.

PEREIRA



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