Quantitative Precipitation Forecast
Issued by NWS

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FOUS11 KWBC 010914
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
414 AM EST SUN FEB 01 2015

VALID 12Z SUN FEB 01 2015 - 12Z WED FEB 04 2015


...CENTRAL PLAINS/MID TO UPPER MISSISSIPPI VALLEY TO NORTHEAST...

QUITE POSSIBLY THE MOST EXTENSIVE WINTER STORM OF THE SEASON WILL
IMPACT PARTS OF THE MIDWEST INTO THE NORTHEAST ON SUN AND MON.  AN
AGGRESSIVE AND SHARP NORTHERN STREAM SHORTWAVE TROUGH WILL AMPLIFY
OVER THE NORTHERN/CENTRAL PLAINS ON SUNDAY AS IT INCORPORATES
SOUTHERN STREAM DYNAMICS AND ANOMALOUS MOISTURE CONTENT EMANATING
FROM THE SOUTHWEST. THIS WILL RESULT IN A SURFACE WAVE DEVELOPING
SUN MORNING OVER THE LOWER MO/MID MS VALLEYS. THIS LOW IS EXPECTED
DEEPEN AND TRACK EASTWARD...REACHING THE LOWER OH VALLEY BY SUN
EVENING AND THE UPPER OH VALLEY/CENTRAL APPALACHIANS BY MON
MORNING.  ANOMALOUS PWS FROM MID-HIGH LEVEL MOISTURE FROM THE
PACIFIC/SUBTROPICAL JET AND LOW-LEVEL GULF OF MEXICO MOISTURE WILL
SURGE OVER AN EXPANDING COLD SECTOR ASSOCIATED WITH A POLAR/ARCTIC
SURFACE RIDGE. THE TREND OF THE GUIDANCE OVER THE LAST FEW DAYS IS
TO GRADUALLY SHIFT NORTHWARD THE WEST TO EAST AXIS OF FROZEN
PRECIP. FOR DAY 1...SUN MORNING INTO EARLY MON...THE GUIDANCE HAS
SETTLED ON A HEAVY SNOWFALL AXIS ALONG THE MICH/IND/OH BORDERS
INTO THE LOWER LAKES REGION...WHERE A SLIGHT TO MODERATE
PROBABILITY OF A FOOT OR MORE HAS BEEN INDICATED.

THE SYSTEM IS EXPECTED TO CONTINUE TO ADVANCE STEADILY DOWNSTREAM
ON DAY 2...MON MORNING INTO EARLY TUE... WITH THE UPPER DYNAMICS
TRANSFERRING FROM THE LOWER LAKES REGION THROUGH THE NORTHEAST.
THE FORECAST CONTINUED AMPLIFICATION OF THE UPPER TROUGH AND
DOWNSTREAM SURFACE RIDGE SHIFTING OFF THE EAST COAST WILL ALLOW
WARM AIR TO SURGE INTO THE REGION...SHIFTING THE HEAVY SNOWFALL
AXIS FURTHER TO THE NORTH INTO PORTIONS OF THE NORTHEAST. A
MODERATE TO HIGH RISK FOR 8 INCHES CENTERS FROM THE UPPER HUDSON
VALLEY INTO CENTRAL AND NORTHERN NEW ENGLAND...WITH SLIGHT RISK
FOR A FOOT OR MORE ON DAY 2.

A WINTRY MIX WITH A SLIGHT RISK FOR ICE ACCUMULATIONS EXCEEDING A
QUARTER INCH IS EXPECTED TO MOVE FROM PORTIONS OF CENTRAL-SOUTHERN
PA ON DAY 1...INTO NORTHERN NJ/SOUTHEASTERN NY/SOUTHERN NEW
ENGLAND ON DAY 2.

OVERALL WPC FOLLOWED A BLEND OF THE GUIDANCE THROUGH EARLY TUE...
INCORPORATING THE NAM/GFS/ECMWF/SREFMEAN.

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

UPPER RIDGING OVER THE PACIFIC NORTHWEST WILL GIVE WAY TO A SERIES
OF LOW AMPLITUDE SHORTWAVES ARRIVING FROM THE PACIFIC TO RAISE THE
THREAT FOR HEAVY SNOWS. THE MAIN RISK APPEARS TO BE FROM THE
NORTHERN WA CASCADES TO THE NORTHERN ROCKIES. WPC FOLLOWED A BLEND
OF THE ECMWF/GFS/NAM/SREF MEAN FOR THE HEAVY SNOW PROBABILITIES
THROUGH DAY 2...DISCOUNTING THE ECMWF BY DAY 3 AS IT LOWERS
HEIGHTS ACROSS THE NORTHWEST MORE AGGRESSIVELY THAN OTHER GUIDANCE.

PEREIRA

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