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V-day snow threat (THE GAINES BOMBER) ( Forecast/ Model/Discussion thread)


Mitchell Gaines

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I agree with Gorse. Someone is going to pop a 5" or 6" snowfall out of this, but outside of the best forcing, accumulations will be limited.

I don't think moisture will be an issue with this system, temps will be. A potent h5 low and southern low in mid february usually have no problems in generating moisture. Though if the surface track ticks south to coming off ne nc then it would put the best lift south of us and hinder the snow chances needed to cool the BL.

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From Paul Kocin at HPC early this morning...

 

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD
235 AM EST TUE FEB 12 2013

VALID 12Z TUE FEB 12 2013 - 12Z FRI FEB 15 2013

...DAYS 1 TO 2...TUESDAY MORNING TO THURSDAY MORNING...

...SOUTHERN PLAINS TO CENTRAL APPALACHIANS/NRN MID-ATL
STATES/SOUTHERN NEW ENGLAND...

A PROGRESSIVE SHORTWAVE TROUGH WILL MOVE EAST NORTHEASTWARD FROM
NEW MEXICO ON TUESDAY MORNING TOWARD THE TENNESSEE VALLEY BY
WEDNESDAY MORNING AND THEN CONTINUE EAST NORTHEASTWARD AND WILL BE
SOUTHEAST OF SOUTHERN NEW ENGLAND BY THURSDAY MORNING. THIS SYSTEM
APPEARS TO BE A RELATIVELY FAST MOVER...BUT ALSO HAS TRENDED
NORTHWARD OVER THE PAST COUPLE DAYS/AS WELL AS MORE DEVELOPED AS
IT MOVES TOWARD THE EAST COAST.  WHILE ITS FAST MOVEMENT LIKELY
PRECLUDES SNOWFALL ACCUMULATIONS GREATER THAN 8 INCHES AT THIS
POINT IN THE FORECAST...SEVERAL AREAS ARE FORECAST TO RECEIVE AT
LEAST LOW TO MODERATE PROBABILITIES OF 4 TO 8 INCHES...BOTH IN
NORTHERN TEXAS/WESTERN OKLAHOMA AND FROM THE MOUNTAINS OF WEST
VIRGINIA ACROSS THE MIDDLE ATLANTIC STATES INTO EXTREME SOUTHERN
NEW ENGLAND.

THE 00Z MODEL RUNS HAVE TRENDED CLOSER TO EACH OTHER WITH THE SNOW
POSSIBILITIES ON DAY 1/TUESDAY FOR THE PANHANDLE OF TEXAS INTO
WESTERN OKLAHOMA. WHILE THE EARLIER OPERATIONAL RUNS OF THE ECMWF
HAVE REMAINED DRIER OVER THIS AREA...THE 00Z RUN HAS NOW INCREASED
WITH PRECIPITATION AMOUNTS...WITH A GENERAL .5 TO 1.0 PRECIP MAX
IN THE AREA...SOME OF WHICH IS RAIN VS SNOW. AS A RESULT OF ALL
THE MODEL AGREEMENT THERE IS AN AREA OF MEDIUM TO HIGH
PROBABILITIES OF GREATER THAN 4 INCHES ACROSS WESTERN OKLAHOMA/NE
TEXAS PANHANDLE...AS WELL AS A LOW PROBABILITY OF GREATER THAN 8
INCHES.

MODEL DIFFERENCES HAVE ALSO NARROWED OVER THE PAST COUPLE DAYS ON
THE RANGE OF SOLUTIONS FOR THE SYSTEM AS IT APPROACHES THE EAST
COAST ON DAY 2. THE 00Z OPERATIONAL RUNS HAVE SLOWED THE FORWARD
MOVEMENT OF THE LOW FROM THE MORNING RUNS... WITH A CONSIDERABLE
LACK OF SPREAD OF SOLUTIONS BY DAY 2. THE 00Z GEFS MEAN AND 21Z
ENSEMBLE MEAN BOTH HAD SIMILAR SOLUTIONS WITH RESPECT TO MEAN
PRECIPITATION AND SUGGEST 4 TO 8 INCH SNOWS FROM NORTHERN WEST
VIRGINIA/NORTHERN MARYLAND ACROSS SE PA/MUCH OF NEW JERSEY/LONG
ISLAND AND EXTREME SOUTHERN NEW ENGLAND.  THE 12Z ECMWF ENSEMBLE
MEANS ARE ABOUT A THIRD DRIER...WHICH HAS BEEN THE PATTERN FOR THE
PAST FEW DAYS.


BY THURSDAY MORNING...THE 12Z NAM/GFS/UKMET/ HAVE NEARLY EXACT
SURFACE LOW POSITIONS SE OF NEW ENGLAND...WITH THE 00Z CANADIAN
SLIGHTLY NORTH AND THE 00Z ECMWF SLIGHTLY SOUTH.  BOTH 00Z
GFS/UKMET HAVE SOLUTIONS PRACTICALLY ON TOP OF EACH OTHER.  WHILE
THERE IS CONFIDENCE THAT SNOW IS LIKELY TO FALL IN PHILADELPHIA TO
NEW YORK CITY...THERE IS LESS CONFIDENCE IN ALL SNOW IN WASHINGTON
D.C./BALTIMORE WITH RAIN CHANGING TO SNOW MORE LIKELY.
THERE IS
ALSO CONFIDENCE THAT IF IT PRECIPITATES IN BOSTON...IT WILL BE
SNOW...BUT THERE IS LESS CONFIDENCE WHETHER BOSTON WILL SEE
SIGNIFICANT SNOW.  THE 00Z ECMWF CONTINUES TO BE THE DRIEST OF THE
OPERATIONAL RUNS OVER THE MID ATLANTIC AND IS A TAD SOUTH OF THE
OTHER MODELS AS THE LOW REACHES THE MID ATLANTIC COAST.    THE 00Z
NAM HAS RUN SLIGHTLY COLDER THAN ITS 18Z RUN AND HAS SNOW FROM
WASHINGTON D.C. TO NEW YORK CITY BUT SOUTH OF BOSTON. AS A
RESULT...THE 00Z GFS/UKMET WERE FOLLOWED MORE CLOSELY WITH RESPECT
TO THE GENERATION OF SNOWFALL PROBABILITIES.

THE BULK OF THE SNOW WILL FALL ACROSS THE MID ATLANTIC STATES AND
SOUTHERN NEW ENGLAND FROM WEDNESDAY EVENING TO THURSDAY MORNING.

 

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To Mt Holly guys:  The AFD mistakingly indicates snow changing to rain from north to south for the V storm rather than the opposite.

 

 

AFTER SUNSET ON WEDNESDAY, WE ARE ANTICIPATING A GRADUAL CHANGE
FROM SNOW TO RAIN, GENERALLY FROM NORTH TO SOUTH
, AS THE SURFACE
FLOW BACKS FROM THE EAST TO THE NORTH. AS PRECIPITATION RATES
INCREASE, COLD AIR WILL LIKELY BE DRAWN DOWN FROM ALOFT ALSO
HELPING TO BRING ABOUT THE CHANGE TO SNOW.

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To Mt Holly guys:  The AFD mistakingly indicates snow changing to rain from north to south for the V storm rather than the opposite.

 

 

AFTER SUNSET ON WEDNESDAY, WE ARE ANTICIPATING A GRADUAL CHANGE

FROM SNOW TO RAIN, GENERALLY FROM NORTH TO SOUTH, AS THE SURFACE

FLOW BACKS FROM THE EAST TO THE NORTH. AS PRECIPITATION RATES

INCREASE, COLD AIR WILL LIKELY BE DRAWN DOWN FROM ALOFT ALSO

HELPING TO BRING ABOUT THE CHANGE TO SNOW.

 

Oops, will fix that. Thanks for catching it.

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