Quantitative Precipitation Forecast
Issued by NWS

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FOUS11 KWBC 040959
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
458 AM EST SUN DEC 04 2016

VALID 12Z SUN DEC 04 2016 - 12Z WED DEC 07 2016


DAYS 1-3...

...PACIFIC NORTHWEST/NORTHERN ROCKIES...

A STRONG COLD FRONT ASSOCIATED WITH A MID/UPPER LEVEL SHORTWAVE
DIGGING SOUTHEAST ACROSS THE REGION IS EXPECTED TO BRING HEAVY
MOUNTAIN SNOWS TO PORTIONS OF THE REGION.  THE HEAVIEST AMOUNTS
ARE EXPECTED TO FOCUS ALONG THE FRONT AS IT SLIDES SOUTH ACROSS
THE OREGON CASCADES AND NORTHERN ROCKIES ON SUN.  ONSHORE FLOW IS
EXPECTED TO SUPPORT SHOWERY CONDITIONS FURTHER TO THE NORTH ACROSS
WESTERN WA.  AS MUCH COLDER AIR FILTERS IN BEHIND THE FRONT SNOW
LEVELS ARE EXPECTED TO DROP TO NEAR THE VALLEY FLOORS OF WESTERN
WA AND OREGON...WHERE LIGHT ACCUMULATIONS ARE POSSIBLE BY SUN
NIGHT-MON MORNING.  PRECIPITATION IS EXPECTED TO DIMINISH BEHIND
THE FRONT BEFORE AN UPSTREAM SHORTWAVE DROPS INTO WESTERN
WA/OREGON ON MON...BRINGING A RENEWED CHANCE FOR HEAVY SNOWS
ACROSS THE OREGON CASCADES WITH LIGHT ACCUMULATIONS POSSIBLE IN
THE COASTAL RANGES AND VALLEYS OF WESTERN OREGON.  PRECIPITATION
IS EXPECTED TO END BY LATE TUE AS THE SHORTWAVE DIGS INTO THE
GREAT BASIN AND A SHORTWAVE RIDGE BEGINS TO BUILD ALONG THE WEST
COAST.

...NORTHERN PLAINS...

THE LEADING SHORTWAVE MOVING ACROSS THE PACIFIC NORTHWEST ON SUN
IS FORECAST TO SWING ACROSS THE NORTHERN PLAINS...ASSUMING A
NEGATIVE TILT AT IT LIFTS ACROSS THE UPPER MIDWEST...WITH A MID
LEVEL CENTER CLOSING OFF NEAR THE RED RIVER OF THE NORTH AS IT
PHASES WITH ENERGY MOVING ACROSS THE CANADIAN PRAIRIE EARLY TUE.
WITH THE BETTER DYNAMICS SHIFTING FURTHER TO THE NORTH INTO
SOUTHERN CANADA...GUIDANCE HAS BEEN BACKING OFF ON SNOW
ACCUMULATIONS ACROSS THE NORTHERN PLAINS.  EXPECT SNOW
ACCUMULATIONS EXCEEDING 4-INCHES TO BE MAINLY LIMITED TO THE
NORTHEASTERN CORNER OF NORTH DAKOTA AND NORTHWESTERN MN...WITH THE
HEAVIEST AMOUNTS ASSOCIATED WITH THE SYSTEM FALLING FURTHER TO THE
NORTH OVER SOUTHERN MANITOBA.

...UPPER MS VALLEY/GREAT LAKES...

A MID-UPPER LEVEL SHORTWAVE CURRENTLY MOVING ACROSS THE
NORTHERN-CENTRAL PLAINS IS EXPECTED TO ASSUME A NEGATIVE-TILT AS
MOVES ACROSS THE MID-UPPER MS VALLEY INTO THE GREAT LAKES SUN
AFTERNOON-EVENING.  GUIDANCE HAS SHOWN AN INCREASING CHANCE FOR
SNOW ACCUMULATIONS OF 4-INCHES OR MORE FROM EASTERN IOWA EASTWARD
INTO NORTHERN IND AND LOWER MI AS AMPLE LOW LEVEL WARM
AIR/MOISTURE ADVECTION INTERACTS WITH THE FAVORABLE FORCING ALOFT.

...CENTRAL ROCKIES/HIGH PLAINS...

THE TRAILING SHORTWAVE MOVING INTO THE PACIFIC NORTHWEST ON MON IS
EXPECTED TO APPROACH THE CENTRAL ROCKIES BY LATE TUE.  UPSLOPE
FLOW IN THE WAKE OF A COLD FRONT DROPPING SOUTH OF THE REGION IN
ADDITION TO THE FAVORABLE UPPER FORCING IS EXPECTED TO SUPPORT AT
LEAST SOME LIGHT SNOWS ACROSS THE REGION BEGINNING LATE TUE AND
CONTINUING INTO THE OVERNIGHT HOURS.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.

PEREIRA

$$





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