Quantitative Precipitation Forecast
Issued by NWS

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FOUS11 KWBC 282104
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
404 PM EST SUN DEC 28 2014

VALID 00Z MON DEC 29 2014 - 00Z THU JAN 01 2015


DAYS 1-3...

...WESTERN U.S....

DURING THE DAY 1 PERIOD...LATE SUN-LATE MON...MODELS SHOW
SHORTWAVE ENERGY CONTINUING TO SLIDE INTO THE BASE OF A LONGWAVE
TROUGH THE GREAT BASIN AND CENTRAL ROCKIES...PRODUCING MAINLY
LIGHT-MODERATE SNOWS ACROSS THE CENTRAL ROCKIES.  WITH LIMITED
MOISTURE...WIDESPREAD ACCUMULATIONS EXCEEDING 8-INCHES ARE NOT
EXPECTED.  MEANWHILE...DEEP NORTHWESTERLY-WESTERLY FLOW IS
EXPECTED TO PERSIST THROUGH THE EARLY PART OF THE PERIOD ALONG THE
PACIFIC NORTHWEST COAST...FOSTERING ADDITIONAL LIGHT-MODERATE
SNOWS ALONG THE NORTHERN-CENTRAL CASCADES INTO THE BLUE MOUNTAINS.
 HERE ALSO...WIDESPREAD ACCUMULATION EXCEEDING 8-INCHES ARE NOT
EXPECTED.

ON DAY 2...LATE MON-LATE TUE...ANY LINGERING SNOW THREAT ACROSS
THE NORTHWESTERN U.S. IS EXPECTED TO END AS AN ARCTIC HIGH SETTLES
INTO THE REGION AND DEEP NORTHEASTERLY FLOW DEVELOPS TO THE NORTH
OF A LOW CLOSING OFF ALONG THE CA-NV BORDER.  EXPECT ANY
SIGNIFICANT SNOWS IN THE WEST TO BE LIMITED TO THE CENTRAL ROCKIES
AND ADJACENT HIGH PLAINS WHERE MID-UPPER DYNAMICS AND OROGRAPHICS
MAY SQUEEZE OUT WHAT LIMITED MOISTURE THERE IS TO PRODUCE SOME 4+
INCH ACCUMULATIONS.

ON DAY 3...LATE TUE-LATE WED...AS THE AFOREMENTIONED UPPER LOW
CONTINUES TO DEEPEN AND SETTLE INTO SOUTHERN CA...BACKING FLOW
ALONG THE COAST IS EXPECTED TO INTRODUCE SOME DEEPER MOISTURE INTO
SOUTHERN CA AND THE SOUTHWEST...PRODUCING LIGHT-MODERATE
PRECIPITATION ACROSS THE REGION.  WHILE THE HEAVIEST SNOW
ACCUMULATIONS ARE EXPECTED TO CENTER ALONG THE SOUTHERN
SIERRA...SOUTHERN CA COASTAL RANGES...MT CHARLESTON IN SOUTHERN
NV...THE SOUTHERN WASATCH AND ALONG THE MOGOLLON RIM IN
NORTHERN-CENTRAL AZ...THIS HAS THE POTENTIAL TO BECOME A
HIGH-IMPACT EVENT AS SNOW LEVELS DROP TO AROUND 2000 FT IN SOME
AREAS ON NEW YEARS EVE.

THE WPC SNOW FORECAST IS MAINLY A REFLECTION OF WPC QPF AND A
BLEND OF THE GFS/ECMWF THERMAL FIELDS.

...CENTRAL APPALACHIANS/MID ATLANTIC STATES...

A LEADING SHORTWAVE DROPPING INTO THE WESTERN U.S. TROUGH IS
FORECAST TO PROGRESS ACROSS THE CENTRAL APPALACHIANS/MID ATLANTIC
STATES ON TUE.  THE NAM/SREF REMAIN AT ODDS WITH REMAINING
GUIDANCE...SHOWING A MORE AMPLIFIED WAVE AND HIGHER AMOUNTS
SPREADING ACROSS THE REGION.  WPC PREFERRED THE FLATTER
CONSENSUS...WITH THE THREAT FOR ANY AMOUNTS EXCEEDING 4-INCHES
LIMITED TO THE HIGHER REACHES OF THE CENTRAL-FAR WESTERN VA AND
CENTRAL WV MOUNTAINS.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.

PEREIRA

$$





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