Quantitative Precipitation Forecast
Issued by NWS

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FOUS11 KWBC 252137
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
435 PM EST SUN JAN 25 2015

VALID 00Z MON JAN 26 2015 - 00Z THU JAN 29 2015

DAYS 1 TO 3...

...OHIO VALLEY/CENTRAL APPALACHIANS/MID-ATLANTIC/NEW YORK/NEW
ENGLAND...

A SHORTWAVE TROUGH AND ASSOCIATED AREA OF LOW PRESSURE MOVING EAST
FROM THE MID MS VALLEY IS FORECAST TO CROSS THE OHIO/TENNESSEE
VALLEYS AND CENTRAL APPALACHIANS OVERNIGHT. THIS SYSTEM WILL BE
AMPLIFYING AS IT CROSSES THE MID-ATLANTIC REGION ON MONDAY AT
WHICH POINT IT WILL BE FOCUSING STRONG CYCLOGENESIS EAST OF THE
VIRGINIA CAPES THROUGH THE DAY. THE MODELS SHOW A WELL-DEFINED
BAND OF STRONGER LOW TO MID LEVEL FRONTOGENESIS JUST NORTH OF THE
SURFACE LOW TRACK THROUGH TONIGHT AND EARLY MONDAY BEFORE THE
ENERGY BEGINS TRANSFERRING TO THE COASTAL LOW DEVELOPMENT JUST OFF
THE MID-ATLANTIC COAST.  SUNDAY...AND THIS WILL RESULT IN A SWATH
OF SEVERAL INCHES OF  SNOWFALL ACROSS THE UPPER OH
VALLEY...CENTRAL APPALACHIANS AND NORTHERN PORTIONS OF THE
MID-ATLANTIC STATES. THE HEAVIEST AMOUNTS ARE GENERALLY FORECAST
FOR THE HIGHER TERRAIN OF WESTERN MD AND SOUTHWEST PA WHERE COLDER
TEMPERATURES COUPLED WITH UPSLOPE WILL TEND TO ENHANCE AMOUNTS A
BIT MORE.

THE LATEST MODELS THOUGH ARE INSISTING THAT THIS STORM WILL EVOLVE
INTO A HIGH IMPACT WINTER STORM/BLIZZARD MONDAY NIGHT AND TUESDAY
FOR PORTIONS OF THE NORTHERN MID-ATLANTIC...EASTERN NEW YORK AND
ADJACENT AREAS OF NEW ENGLAND. THIS INCLUDES MAJOR METROPOLITAN
AREAS ALONG THE I-95 CORRIDOR FROM PHILADELPHIA NORTHEAST THROUGH
NEW YORK CITY AND UP TO BOSTON. THE MODELS DEPICT A POWERFUL
DEFORMATION ZONE DEVELOPING AND SPREADING INLAND IN RESPONSE TO
RAPIDLY DEEPENING LOW PRESSURE OFF THE MID-ATLANTIC COAST THAT
WILL LIFT NORTHEAST TO NEAR THE BENCHMARK BY EARLY TUESDAY BEFORE
THEN SLOWING DOWN AND ONLY GRADUALLY LIFTING TO NEAR THE GULF OF
MAINE ON WEDNESDAY. THE INTERIOR AREAS OF THE NORTHEAST ALONG AND
ADJACENT THE I-95 CORRIDOR ARE EXPECTED TO SEE VERY INTENSE
SNOWFALL AS VERY STRONG FRONTOGENETIC FORCING...ATLANTIC MOISTURE
TRANSPORT AND UPPER JET DYNAMICS COMBINE FOR INTENSE SNOWFALL
RATES. ASIDE FROM THE FAVORABLE SYNOPTIC SCALE SET-UP...THE SET-UP
IS PERFECT ON THE SMALLER SCALE FOR MESOSCALE BANDING FEATURES
THAT WILL INCLUDE A CONVECTIVE ELEMENT TO THE SNOWFALL. THE LATEST
GUIDANCE TENDS TO FAVOR THE BEST LIKELIHOOD FOR THIS TO BE AROUND
NEW YORK CITY NORTHEAST TOWARD THE BOSTON AREA ALONG WITH AREAS
JUST WEST OF THIS LINE. THE RESULT WILL BE EVEN HEAVIER SNOWFALL
RATES THAT COULD BE ON THE ORDER OF 2 TO 4 INCHES/HR AND WILL
RESULT IN VERY HEAVY STORM TOTALS. ADDITIONALLY THERE IS A
LIKELIHOOD FOR BLIZZARD CONDITIONS TO IMPACT MANY AREAS FROM
CENTRAL/NORTHERN NEW JERSEY NORTH UP ACROSS SOUTHEAST NEW YORK AND
ALL OF SOUTHERN AND EASTERN NEW ENGLAND DUE TO THE EXPECTATION OF
HIGH WINDS. THE STORM SHOULD GRADUALLY WEAKEN LATER TUESDAY AND
BEGIN TO PULL AWAY BY LATER WEDNESDAY FROM THE NORTHEAST...BUT
HEAVY SNOWFALL ASSOCIATED WITH THE AFOREMENTIONED DEFORMATION ZONE
WILL EXTEND THROUGH ALL OF NEW ENGLAND. STORM TOTAL AMOUNTS AS
HIGH AS 1 TO 3 FEET CAN BE EXPECTED...WITH THE HEAVIEST AMOUNTS
GENERALLY FROM NEAR NEW YORK CITY UP TO NEAR BOSTON.


...UPPER GREAT LAKES...

ANOTHER IN A SERIES OF SHORTWAVES/CLIPPERS WILL ADVANCE SOUTHEAST
OUT OF CANADA AND INTO THE UPPER MIDWEST TONIGHT AND MONDAY. A NEW
STREAK OF WARM ADVECTION AND LOW LEVEL CONVERGENCE OVER LAKE
SUPERIOR AND ADJACENT LAND AREAS INCLUDING THE U.P. OF MICHIGAN
WILL FAVOR A BAND OF ACCUMULATING SNOWFALL. THE LACK OF AVAILABLE
MOISTURE AND OVERALL FORCING SHOULD PREVENT AMOUNTS FROM BEING TOO
HEAVY...BUT A FEW INCHES CAN BE EXPECTED.


...SIERRA-NEVADA/GREAT BASIN/ROCKIES...

AN UPPER LOW THAT IS CURRENTLY SITUATED JUST WEST OF THE BAJA
PENINSULA IS FORECAST TO GRADUALLY LIFT NORTH ON MONDAY IN
RESPONSE TO AN UPSTREAM TROUGH DIGGING ACROSS THE EASTERN PACIFIC.
AS THE UPPER TROUGH MOVES NORTH ACROSS SOUTHERN CALIFORNIA MONDAY
NIGHT A DIVERGENCE MAXIMA ALOFT IS EXPECTED TO CROSS SOUTHERN
CALIFORNIA INTO THE SOUTHERN SIERRA RANGE. LOW LEVEL SOUTHEAST
WINDS TRANSPORT MOISTURE INTO THE MOUNTAINS
THERE SHOULD BE SEVERAL INCHES OF SNOW FOR THE HIGHER ELEVATIONS
OF THE SOUTHERN TO CENTRAL SIERRA-NEVADA.

THE UPPER TROUGH WILL SHEAR DOWNSTREAM LATER TUESDAY AND WEDNESDAY
ACROSS THE GREAT BASIN AND INTO THE NORTH-CENTRAL ROCKIES. THE
ENERGY ALOFT COUPLED WITH FAVORABLE MID LEVEL MOISTURE TRANSPORT
AND UPSLOPE FLOW WILL FAVOR LOCALLY HEAVY SNOWFALL FOR THE
NORTHERN PORTIONS OF THE WASATCH AND INTO THE TETONS. THE WESTERN
COLORADO HIGH COUNTRY WILL ALSO SEE ACCUMULATING SNOW. SNOW
AMOUNTS LOCALLY ARE EXPECTED TO EXCEED 6 INCHES FOR THESE AREAS.


THE PROBABILITY OF 0.25 INCH OR GREATER ICING IS LESS THAN 10
PERCENT.

ORRISON

$$





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