Quantitative Precipitation Forecast
Issued by NWS

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FOUS11 KWBC 222128
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
427 PM EST MON JAN 22 2018

VALID 00Z TUE JAN 23 2018 - 00Z FRI JAN 26 2018

...UPPER MISSISSIPPI VALLEY/GREAT LAKES...

THE DYNAMIC STORM THAT BROUGHT BLIZZARD CONDITIONS AND OVER A FOOT
OF SNOW TO PORTIONS OF THE CENTRAL PLAINS ON MONDAY WILL LIFT
THROUGH THE UPPER GREAT LAKES MONDAY NIGHT.  ALTHOUGH THE SYSTEM
SHOULD BEGIN TO GRADUALLY WEAKEN...A SWATH OF MODERATE TO HEAVY
SNOW IS STILL EXPECTED WITHIN THE DEFORMATION AXIS SETTING UP
NORTH AND WEST OF THE SURFACE LOW TRACK...ESPECIALLY OVER THE U.P.
OF MICHIGAN WHERE WINDS OFF LAKE SUPERIOR SHOULD HELP ENHANCE
SNOWFALL TOTALS.  ALSO...A NARROW TRANSITION ZONE CONTAINING SLEET
AND FREEZING RAIN WILL CONTINUE TO BE POSSIBLE WITHIN WARM
ADVECTION PRECIPITATION DEVELOPING AHEAD OF THE STORM.  THE CHANCE
FOR WINTRY PRECIPITATION SHOULD DIMINISH ACROSS THE UPPER
MISSISSIPPI VALLEY AND UPPER GREAT LAKES TUESDAY AFTERNOON WHILE
THE SYSTEM LIFTS FARTHER NORTHEASTWARD INTO SOUTHERN ONTARIO.  THE
LATEST DAY 1 (00Z TUE - 00Z WED) WPC PROBABILITIES ARE ADVERTISING
A MODERATE RISK OF GREATER THAN 4 INCH SNOWFALL ACCUMULATIONS
ACROSS MUCH OF THE U.P. OF MICHIGAN...WITH A SMALLER SLIGHT RISK
AREA OF GREATER THAN 8 INCH SNOWFALL ACCUMULATIONS CENTERED OVER
MARQUETTE.  CURRENT WPC PROBABILITIES FOR ICE ACCUMULATIONS
GREATER THAN 0.25 INCHES ARE LESS THAN 10% ACROSS THE REGION.



...NORTHEAST...

WARM ADVECTION PRECIPITATION AHEAD OF A DYNAMIC STORM LIFTING OUT
OF THE CENTRAL PLAINS ON MONDAY WILL SPREAD THROUGH THE NORTHEAST
MONDAY NIGHT.  A COLD AIR MASS IN PLACE WILL ALLOW PRECIPITATION
TO START AS SNOW ACROSS MUCH OF NORTHERN NEW ENGLAND...BUT THEN
MODEL THERMAL PROFILES SUGGEST ENOUGH WARM AIR NOSING IN ALOFT
SHOULD CAUSE SNOW TO TRANSITION TO FREEZING RAIN AND EVENTUALLY
RAIN BY TUESDAY AFTERNOON.  DAY 1 (00Z TUE - 00Z WED) WPC
PROBABILITIES ARE SHOWING THE GREATEST CHANCE FOR SNOWFALL IN
EXCESS OF 4 INCHES WILL BE ACROSS THE NORTHERN HALF OF
MAINE...WHILE THE RISK FOR ICE ACCUMULATIONS GREATER THAN 0.25
INCHES EXTENDS SOUTHWARD INTO NEW HAMPSHIRE.  THEN AS THE STORM`S
SURFACE LOW TRACKS INTO SOUTHERN CANADA AND COLD FRONT SWEEPS OFF
THE NORTHEAST COAST TUESDAY NIGHT...COOLING CONDITIONS AND
CYCLONIC FLOW ON THE BACKSIDE OF THE SYSTEM SHOULD START LAKE
EFFECT SNOW DOWNWIND OF THE GREAT LAKES...WITH WPC DAY 2 (00Z WED
- 00Z THU) PROBABILITIES CURRENTLY ADVERTISING A SLIGHT RISK OF
SNOWFALL EXCEEDING 4 INCHES DOWNWIND OF THE LOWER LAKES.


...PACIFIC NORTHWEST AND CALIFORNIA TO THE NORTHERN INTERMOUNTAIN
WEST AND ROCKIES...

A LARGE UPPER VORTEX NEAR THE GULF OF ALASKA/NORTHEASTERN PACIFIC
WILL STEER A POTENT SHORTWAVE TROUGH AND TREMENDOUS FETCH OF
PACIFIC MOISTURE INTO THE NORTHWEST ON TUESDAY.  WARM ADVECTION
AHEAD OF THE SYSTEM WILL INITIALLY RAISE SNOW LEVELS...BUT HEAVY
OROGRAPHIC SNOW IS STILL ANTICIPATED FOR THE HIGHER ELEVATIONS OF
THE OLYMPICS...WASHINGTON/OREGON CASCADES...BLUE MOUNTAINS...AND
NORTHERN BITTERROOTS.  THEN ON WEDNESDAY INTO THURSDAY...THE
ENTIRE LARGE SCALE TROUGH OVER THE EASTERN PACIFIC WILL EDGE
INLAND OVER THE WESTERN U.S..  THE LOWERING HEIGHTS...COMBINED
WITH AN ACTIVE UPPER-LEVEL JET SHOULD RESULT IN WIDESPREAD HEAVY
SNOWFALL FROM THE PACIFIC NORTHWEST AND NORTHERN CALIFORNIA TO THE
NORTHERN INTERMOUNTAIN WEST AND ROCKIES.  WPC PROBABILITIES ARE
ADVERTISING THE CHANCE FOR SNOWFALL ACCUMULATIONS TO EXCEED A FOOT
OVER MUCH OF THE HIGHER TERRAIN...WITH CONSECUTIVE DAYS OF
SNOWFALL ACCUMULATIONS EXCEEDING A FOOT POSSIBLE FOR THE
OLYMPICS...WASHINGTON CASCADES...AND SHASTA/TRINITY RANGE IN
NORTHERN CALIFORNIA.


GERHARDT




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