Quantitative Precipitation Forecast
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FOUS11 KWBC 012132
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
431 PM EST THU DEC 01 2016

VALID 00Z FRI DEC 02 2016 - 00Z MON DEC 05 2016

DAY 1 TO 3...


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

AN ACTIVE PATTERN WILL CONTINUE ACROSS THE NORTHWESTERN CORNER OF
THE NATION LATE THIS WEEK AND THROUGH THE WEEKEND.  INITIALLY SNOW
SHOULD BE LIGHT TO MODERATE AND MAINLY CONFINED TO THE HIGHER
ELEVATIONS OF THE CASCADES AND NORTHERN ROCKIES...BUT THEN HEAVIER
AND MORE SIGNIFICANT SNOW WILL BE POSSIBLE AS SHORTWAVE ENERGY
WITHIN THE LEADING EDGE OF AN AMPLIFYING UPPER TROUGH PROGRESSES
INTO THE NORTHWEST SATURDAY NIGHT.  STRONG SYNOPTIC FORCING
COMBINED WITH MOIST FLOW INTO THE TERRAIN AND LOWERING SNOW LEVELS
WILL BRING PERIODS OF HEAVY SNOW TO THE CASCADES...WITH THE FOCUS
FOR HEAVY SNOW SHIFTING TO THE NORTHERN ROCKIES ON SUNDAY AS THE
SHORTWAVE EJECTS EASTWARD AND A SURFACE LOW POSSIBLY DEEPENS IN
THE NORTHERN HIGH PLAINS/SOUTH CENTRAL CANADA.  WPC ENSEMBLE
GUIDANCE CURRENTLY HAS A SLIGHT RISK (AT LEAST A 10% PROBABILITY)
OF SNOWFALL EXCEEDING A FOOT OVER THE WASHINGTON CASCADES AND
NORTHERN ROCKIES DAY 3 (00Z SUN THROUGH 00Z MON)...BUT
PROBABILITIES COULD INCREASE AS MODELS COME INTO BETTER AGREEMENT
OVER THE NEXT FEW CYCLES.  FOR DETAILS ON MODEL DIFFERENCES WITH
THE SHORTWAVE...PLEASE REFER TO WPC`S PMDHMD.


...SOUTHERN ROCKIES/SOUTHERN PLAINS...

A DEEPENING TROUGH OVER THE SOUTHWEST ON FRIDAY WILL RESULT IN AN
INCREASING PRECIPITATION SHIELD ACROSS PORTIONS OF NEW MEXICO INTO
TEXAS FRIDAY INTO SATURDAY. MOST OF THIS WILL BE IN THE FORM OF
RAIN...ALTHOUGH COLD AIR WORKING IN FROM THE NORTH WILL ATTEMPT TO
CHANGE PRECIPITATION TO SNOW FROM PORTIONS OF THE OKLAHOMA AND
TEXAS PANHANDLE INTO EASTERN NEW MEXICO.  THERE REMAINS A LOT OF
UNCERTAINTY WITH REGARDS TO THE TIMING/MAGNITUDE OF THE COLD AIR
AND HOW THIS MAY OR MAY NOT OVERLAP WITH FALLING PRECIPITATION.
THE BULK OF THE LATEST MODEL GUIDANCE CONTINUES TO TREND TOWARDS
THE POTENTIAL FOR AT LEAST LIGHT ACCUMULATIONS...BUT THERMAL
PROFILES STILL SEEM MARGINAL FOR SUPPORTING SNOW IN THE LOWER
ELEVATIONS.  THE WPC ENSEMBLE BLEND CURRENTLY HAS A SLIGHT RISK
(AT LEAST A 10% PROBABILITY) OF GREATER THAN FOUR INCHES OF SNOW
EXTENDING FROM THE SOUTHERN ROCKIES OF NEW MEXICO INTO NORTH TEXAS
AND THE OKLAHOMA PANHANDLE.  PLEASE REFER TO WPC`S QPFPFD  FOR
INFORMATION ON THE HEAVY RAINFALL THREAT WITH THIS SYSTEM.


...LOWER GREAT LAKES/NEW ENGLAND...

HEAVY SNOW OVER NORTHERN MAINE SHOULD COME TO AN END THURSDAY
EVENING AS A SURFACE LOW AND PLUME OF MOISTURE LIFT FARTHER AWAY
FROM THE NEW ENGLAND COAST.  NORTHWESTERLY FLOW BEHIND THE
DEPARTING LOW PRESSURE SHOULD FOSTER RAIN AND SNOW SHOWERS
DOWNWIND OF THE LOWER LAKES AND OVER THE UPSLOPE SIDE OF THE
TERRAIN OF INTERIOR NEW ENGLAND THROUGH SATURDAY...BUT THEN
ACTIVITY SHOULD DIMINISH AS SHORTWAVE RIDGING SLIDES IN ALOFT ON
SUNDAY.  MODEL SNOWFALL OUTPUT WAS IN GOOD AGREEMENT WITH KEEPING
ACCUMULATIONS LIGHT ACROSS THE REGION...WITH ENSEMBLE GUIDANCE
SUGGESTING THE GREATEST CHANCE FOR SNOWFALL TOTALS IN EXCESS OF
FOUR INCHES WILL BE OVER THE ADIRONDACKS/TUG HILL PLATEAU OF NEW
YORK.


THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.


GERHARDT

$$





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