Quantitative Precipitation Forecast
Issued by NWS

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FOUS11 KWBC 012055
QPFHSD

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

VALID 00Z MON FEB 02 2015 - 00Z THU FEB 05 2015


...GREAT LAKES TO NORTHEAST...

THE START OF POSSIBLY THE MOST EXTENSIVE WINTER STORM OF THE
SEASON IS IMPACTING PARTS OF THE MIDWEST TODAY... INCLUDING THE
BLIZZARD CONDITIONS AROUND CHICAGO METRO AREA.. AND SHOULD BEGIN
TO AFFECT PARTS OF THE GREAT LAKES INTO THE NORTHEAST FOR MON. AN
AGGRESSIVE AND SHARP NORTHERN STREAM SHORTWAVE TROUGH
INCORPORATING SOUTHERN STREAM DYNAMICS AND ANOMALOUS MOISTURE
CONTENT IS AMPLIFYING OVER THE WRN OH VALLEY. A SURFACE LOW
ORGANIZING OVER IL AT THE MOMENT IS EXPECTED DEEPEN AND TRACK
NORTHEASTWARD...REACHING WRN PA BY MON MORNING. ANOMALOUS PWS FROM
MID-HIGH LEVEL MOISTURE FROM THE PACIFIC/SUBTROPICAL JET AND
LOW-LEVEL GULF OF MEXICO MOISTURE IS SURGING OVER AN EXPANDING
COLD SECTOR ASSOCIATED WITH A POLAR/ARCTIC SURFACE RIDGE. THE
UPPER DYNAMICS OF THIS SYSTEM SHOULD TRANSFER TO THE NORTHEAST
COAST MON AFTN/EVENING TO ALLOW A COASTAL LOW TO FLOURISH UP THE
NORTHEAST COAST. THE OVERALL AMPLIFICATION OF THIS UPPER TROUGH
AND DOWNSTREAM SURFACE RIDGE RETREATING RAPIDLY OFF THE EAST COAST
WILL ALLOW WARM AIR TO SURGE NORTH...WITH THE CONSENSUS OF THE 12Z
GUIDANCE SHIFTING THE HEAVY SNOWFALL AXIS FURTHER TO THE NORTH.
THE HEAVIEST SNOWFALL SUN TO MON EVENING WILL BE FROM SRN LOWER MI
THROUGH WRN NY INTO THE INTERIOR PARTS OF THE NORTHEAST AND UP THE
NEW ENGLAND COAST. WPC GENERALLY FOLLOWED A BLEND OF THE GUIDANCE
AS THE OVERALL FORECAST SPREAD HAS NARROWED SIGNIFICANTLY AND THE
LARGEST SNOWFALL PROBS ISSUED WILL BE A LOW TO MODERATE RISK FOR
12 INCHES FROM SWRN NY/EXTREME NWRN PA INTO THE HUDSON VALLEY
ACROSS INTERIOR NEW ENGLAND OR SRN NH/VT AND NRN MA TO COASTAL
MAINE.

...PACIFIC NORTHWEST INTO THE NRN INTER-MOUNTAIN WEST...

UPPER RIDGING OVER THE BEGINNING OF THE WEEKEND FOR THE PACIFIC
NORTHWEST IS GIVING WAY RAPIDLY WITH A SHORT WAVE ARRIVING INTO
THE REGION TODAY FOLLOWED BY A SERIES OF LOW AMPLITUDE PAC
IMPULSES TO RAISE THE THREAT FOR HEAVY SNOWS. THE MAIN RISK
APPEARS TO BE AWAY FROM THE CONSTANT MOISTURE PLUME/PAC MOISTURE
TRANSPORT ARRIVING INTO OR/NRN CA THE NEXT COUPLE OF DAYS AND MORE
TOWARD FAVORABLE OROGRAPHICS AND STATIONARY POLAR BOUNDARY
STRETCHING FROM THE NRN TO CENTRAL ROCKIES. WPC FOLLOWED A BLEND
OF THE ECMWF/GFS FOR THE HEAVY SNOW PROBABILITIES FROM THE WA
CASCADES INTO THE NRN ROCKIES/BITTERROOTS AND TETONS/NRN CO
ROCKIES... WHILE STRETCHING INTO THE COLD SECTOR ACROSS ERN MT/WY
AND WRN NE.

...GREAT LAKES/OH VALLEY LATE TUES/EARLY WED...

WEAK SHORT WAVE IMPULSE STREAKING ACROSS THE FAIRLY ZONAL FLOW
FROM THE WEST COAST INTO THE PLAINS... WILL BEGIN TO DEEPEN A BIT
LATE TUES INTO WED AHEAD OF A DIGGING UPPER TROUGH AND SURGE OF
ARCTIC AIR. THIS WILL RESULT IN A SMALL POCKET OF WARM ADVECTION
LIGHT SNOW FROM LAKE MI TO LAKES ERIE/ONTARIO. THE SMALL SCALE
NATURE OF THIS FEATURE ON A DAY 3 INTRODUCES SOME MODEL SPREAD BUT
WPC STAYED CLOSELY TO A BLEND OF THE GFS/ECMWF TO INTRODUCE LOW
PROB OF 4 INCHES ACROSS PARTS OF THE REGIONS.

MUSHER

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