Quantitative Precipitation Forecast
Issued by NWS

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FOUS11 KWBC 060938
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
437 AM EST TUE DEC 06 2016

VALID 12Z TUE DEC 06 2016 - 12Z FRI DEC 09 2016


DAYS 1-3...

...NORTH DAKOTA/MINNESOTA...

SNOWS ARE EXPECTED TO CONTINUE THROUGH THE MORNING INTO THE
AFTERNOON HOURS ON TUE ACROSS PORTIONS OF EASTERN NORTH DAKOTA AND
NORTHWESTERN MN AS AN UPPER LOW CONTINUES TO DEEPEN WHILE SPINNING
TO  THE EAST ACROSS THE REGION.  THE HEAVIEST SNOW ACCUMULATIONS
ARE EXPECTED TO FOCUS ALONG THE NORTHERN NORTH DAKOTA/MINNESOTA
BORDER...WHERE ADDITIONAL AMOUNTS OF 4-INCHES OR MORE ARE LIKELY.
BLOWING SNOWS DRIVEN STRONG NORTHWESTERLY WINDS ON THE BACKSIDE OF
THE SYSTEM ARE EXPECTED TO CREATE POOR VISIBILITIES AND HAZARDOUS
DRIVING CONDITIONS ACROSS MUCH OF NORTH DAKOTA INTO NORTHWESTERN
MN ON TUE.

...GREAT LAKES...

UPPER LOW IMPACTING THE NORTHERN PLAINS/UPPER MIDWEST ON TUE IS
FORECAST TO LIFT INTO SOUTHERN CANADA...TRANSITIONING TO AN OPEN
WAVE AS IT MOVES FROM SOUTHERN ONTARIO INTO SOUTHERN QUEBEC WED
NIGHT.  STRONG COLD AIR ADVECTION AND DEEP CYCLONIC NORTHWEST TO
WEST FLOW IN THE WAKE OF THE SYSTEM WILL SET THE STAGE FOR LAKE
EFFECT SNOWS PRODUCING LOCALLY HEAVY ACCUMULATIONS...BEGINNING WED
ACROSS UPPER MICH BEFORE EXTENDING INTO LOWER MICH AND INTO THE
LEE OF THE LOWER LAKES AS WELL BY EARLY THU.

...CENTRAL ROCKIES...

A SHORTWAVE TROUGH DIVING ACROSS THE PACIFIC NORTHWEST ON TUE WILL
APPROACH THE CENTRAL ROCKIES BY EARLY WED...PRODUCING SOME LIGHT
TO MODERATE SNOWS ALONG THE RANGES OF SOUTHEASTERN WYOMING AND
COLORADO TUE NIGHT INTO WED MORNING.  POST-FRONTAL UPSLOPE FLOW
ACCENTUATED BY A SURFACE LOW DROPPING SOUTHEASTWARD ACROSS
SOUTHERN COLORADO WILL HELP DEVELOP SNOWS FURTHER EAST OUT INTO
THE CENTRAL HIGH PLAINS.  HOWEVER...LIMITED MOISTURE AND THE
PROGRESSIVE NATURE OF THE SYSTEM ARE EXPECTED TO LIMIT
ACCUMULATIONS...WITH WIDESPREAD HEAVY ACCUMULATIONS NOT EXPECTED.

...CENTRAL APPALACHIANS TO THE NORTHEAST...

A REMNANT SHORTWAVE TROUGH ASSOCIATED WITH THE LOW CURRENTLY
LIFTING INTO THE LOWER MS VALLEY IS EXPECTED TO TRACK INTO THE MID
ATLANTIC STATES WITH ON TUE.  AN INITIAL SURFACE LOW MOVING FROM
THE TN/OH VALLEYS WILL GIVE WAY TO A LOW DEVELOPING OFF OF THE NC
COAST.  WARM MOIST AIR MOVING ACROSS THE TOP OF COLD AIR ALREADY
IN PLACE IS EXPECTED TO SUPPORT A PERIOD OF MIXED PRECIPITATION
WITH SOME LIGHT ICE ACCUMULATIONS ALONG THE MOUNTAINS OF EASTERN
WV/WESTERN VA/FAR WESTERN MD INTO SOUTHWESTERN PA ON TUE.
EVAPORATIVE COOLING WILL HELP SUPPORT SNOWS FURTHER TO THE NORTH
ACROSS NORTHERN PA INTO WESTERN AND CENTRAL NY.  MARGINAL BOUNDARY
LAYER TEMPS AND ISOTHERMAL PROFILES ALOFT CONTINUE MAKE THIS
FORECAST A CHALLENGE...HOWEVER AT LEAST LIGHT SNOW ACCUMULATIONS
APPEAR LIKELY ESPECIALLY ACROSS THE HIGHER TERRAIN OF NORTHERN PA
INTO THE SOUTHERN TIER OF NY ON TUE/TUE NIGHT.

...PACIFIC NORTHWEST TO THE NORTHERN ROCKIES...

A SHORTWAVE TROUGH IS FORECAST TO DROP SOUTHEAST ACROSS THE
REGION...PRODUCING MAINLY LIGHT PRECIPITATION ACROSS THE REGION ON
TUE.  THIS WILL BE FOLLOWED BY DRYING CONDITIONS AS A SHORTWAVE
RIDGE MOVES ACROSS THE REGION ON WED.  LOW LEVEL COLD AIR WILL
REMAIN ENTRENCHED ACROSS THE REGION HOWEVER...SETTING THE STAGE
LOW ELEVATION MIXED PRECIPITATION AS THE NEXT SYSTEM APPROACHES
THE COAST WED NIGHT.  WARM MOIST AIR MOVING ACROSS THE TOP OF THE
COLD AIR IS EXPECTED TO PRODUCE A VARIETY OF PRECIPITATION TYPES
ACROSS THE PACIFIC NORTHWEST INTO THE INTERMOUNTAIN
WEST...INCLUDING FREEZING RAIN WITH ACCUMULATING ICE IN THE BASINS
AND VALLEYS WHERE THE COLD AIR REMAINS ENTRENCHED.  EASTERLY FLOW
IN THE BOUNDARY LAYER IS EXPECTED TO HELP MAINTAIN THE COLD AIR
EAST OF THE CASCADES BEFORE SOUTHWESTERLY WINDS PREVAIL.  WHILE
WIDESPREAD HEAVY ICE ACCUMULATIONS ARE NOT EXPECTED...SEVERAL
AREAS FROM THE PACIFIC NORTHWEST INTO THE INTERMOUNTAIN WEST MAY
SEE AT LEAST SOME MINOR ICE ACCUMULATIONS LATE WED INTO THU.
MEANWHILE THE THREAT FOR HEAVY SNOWS IS EXPECTED TO INCREASE
ACROSS THE HIGHER TERRAIN OF THE NORTHERN CASCADES INTO THE
NORTHERN ROCKIES AS THE SYSTEM MOVES INLAND THU INTO EARLY FRI.

PEREIRA

$$





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