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February 12-13 Storm, Part III: Trilogy ends and then Obs thread soon!

stormtracker

By stormtracker,
in Mid Atlantic

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StudentOfClimatology

StudentOfClimatology

Posted
Posted

Very detailed AFD just out of LWX:

DEWPOINTS IN THE SINGLE DIGITS AND TEENS UP UNTIL THE

PRECIP ARRIVES FROM THE SOUTH. IMPORTANT BECAUSE IT WILL HELP KEEP

TEMPS /SFC AND THROUGHOUT THE COLUMN/ BELOW FREEZING AND PRECIP WILL

BE ALL SNOW AS IT COMES IN LATE TONIGHT.

LATE TONIGHT INTO EARLY THU...

THE HEFTY AMOUNTS OF CLOUD DEBRIS COMING IN JUST AHEAD OF THE PRECIP

SHIELD WILL MAKE EASILY OVERCOME THE DRY MID LEVELS WITHIN A

RELATIVELY BRIEF FEW HRS LATER THIS AFTN. NOW W/ SOME NEAR TERM

HI-RES MODELS COMING ONTO THE SCOPE...SOME MORE EXACT TIMING CAN BE

ASSESSED. BY THE LATE AFTN HRS...WHAT WILL LIKELY BE A LARGE SECTION

OF VIRGA WILL SPREAD NWD TOWARD THE AREA - ENCOMPASSING THE SRN TIER

OF THE CWA NEAR THE I-64 CORRIDOR TOWARD THE LATE AFTN HRS - 4-6PM

OR SLIGHTLY LATER. WITHIN A COUPLE OF HRS AFTER THIS...LIGHT SNOW

WILL LIKELY REACH THE SFC AND GRADUALLY INCREASE IN INTENSITY THRU

THE REST OF THE EVE/NIGHTTIME HRS.

THIS INITIAL WAVE OF PRECIP WILL BE FAIRLY SOLID AS IT COVERS THE

CAROLINAS AND MUCH OF SRN VA BEFORE COASTAL LOW TRANSITION TAKES

PLACE. THE AXIS OF PRECIP WILL BE MORE WEST-TO-EAST...THEN PIVOTING

NE-SW AS THE TRANSITION TAKES PLACE. LARGE-SCALE ASCENT AND PLENTY

OF GULF MOISTURE IS IN PLACE. FOR ONE...THE ECMWF AND RELATED

ENSEMBLES HAVE BEEN CONSISTENT W/ LITTLE WAVERING OVER TOTAL QPFS

WHICH RANGE BETWEEN 0.5-1.0" LIQUID EQUIV ACROSS THE AREA - MUCH OF

THAT ARRIVING W/ THIS FIRST BATCH OF PRECIP WRAPPED AROUND THE HEAD

OF THE DEVELOPING COASTAL LOW PRES SYSTEM. THE EURO IS ALSO

MAINTAINING A LONGER RESIDENCE TIME FOR THE STORM SYSTEM - KEEPING

PRECIP AROUND WELL INTO THE NIGHTTIME HRS ON THU. THE GFS/NAM HAVE

BEEN LEANING ON THE LIGHTER SIDE OF QPF AND SHOWING A SLIGHTLY

FASTER EXIT TO THE SYSTEM...MIDDAY/EVE THU. THE 06Z NAM HOWEVER HAS

SPLASHED A BIT HIGHER QPF ONTO THE PREV RUN HOWEVER AND LOOKS MORE

LIKE THE ECM SOLN.

THURSDAY...

LATEST SREF SNOW RATIOS SHOW A BROAD 10-12:1 REGIME FROM THE I-95

CORRIDOR AND WEST - WHILE THE BAY TO I-95 IS SPREAD BETWEEN 5-10:1.

AS W/ MOST WINTRY COASTAL STORM SYSTEMS...MIXING OF SLEET/RAIN

WITHIN 50-100 MILES OF THE SFC LOW ALWAYS A FACTOR FOR OUR REGION.

THE DAYTIME HRS OF THU WILL BE NO DIFFERENT W/ PERIODS OF MIXED

PRECIP ALONG AND E OF THE I-95 CORRIDOR FROM MID MRNG THRU LATE EVE

W/ THE POSSIBLE BRIEF CHANGING OVER TO ALL SNOW W/ WHAT LITTLE

PRECIP IS STILL LEFTOVER AT THAT TIME. EVEN W/ THE POTENTIAL FOR

RANGE OF ACCUMULATING SNOW ACROSS SRN MD/COUNTIES ALONG THE BAY AND

PARTS OF THE ERN DC METRO SUBURBS FROM THE FIRST WAVE OF PRECIP...

TOTAL AMOUNTS MAY BE LOWERED FROM THE MIXING OF RAIN/SLEET AND EVEN

SFC TEMPS WAVERING AROUND OR JUST ABOVE FREEZING FOR ANY LENGTH OF

TIME MIDDAY.

THIS WILL BE LESS OF AN ISSUE THE TIER OF COUNTIES JUST WEST OF I-95

IN NRN VA AND MD...AND THIS CONTINUES TO BE THE QPF AXIS FOR MANY

GUIDANCE MEMBERS AS WE NEAR THE ONSET OF THE SYSTEM. AS THE

"COMMA-HEAD" PRECIP ZONE OF THE LOW PRESSURE SYSTEM PIVOTS ALONG THE

ERN SEABOARD INTO THU MRNG/AFTN...THIS IS THE TIME PERIOD WHERE MORE

INTENSE SNOW BANDS CAN DEVELOP - INCREASING SFC WINDS AND DROPPING

VSBYS. THIS IS ALSO WHEN DRIER AIR CAN GET ENTRAINED INTO PARTS OF

THE SYSTEM AND BEGIN TO CUT OFF PRECIP IN CERTAIN AREAS - WHILE

ENHANCING NEARBY BANDS. THIS MAKES THE SECOND PHASE OF THIS SYSTEM

TRICKY TO FORECAST...WHERE AREAS THAT RECEIVED MODEST SNOWFALL

AMOUNTS BEFORE IT CAN GET ANOTHER QUICK FEW INCHES DEPENDING ON

WHERE THE MOST INTENSE BAND(S) SETS UP AND HOW LONG IT LASTS.

FOR THE CURRENT FORECAST CYCLE UPDATE...INCREASE SNOWFALL TOTALS

WITHIN THE AXIS THAT IS CENTERED ON THE BLUE RIDGE - W/ JUST OVER A

FOOT OF STORM-TOTAL SNOW ACROSS THIS AREA AND TAPERING OFF ON

EITHER SIDE. THE ENTIRE CWA OUTSIDE OF ST MARYS AND CALVERT CO ARE

UNDER A WINTER STORM WARNING BEGINNING LATE TONIGHT AND LASTING THRU

MID-LATE IN THE DAY ON THU.

-- End Changed Discussion --

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wxmeddler

wxmeddler

Posted
Posted

Hot off the press:


PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
432 AM EST WED FEB 12 2014

VALID 12Z WED FEB 12 2014 - 12Z SAT FEB 15 2014
....
THIS LOW WILL INTENSIFY RAPIDLY
AND TRACK NORTHEASTWARD UP ALONG THE MID ATLANTIC/NORTHEAST
COAST... AS THE PHASED TROUGH ASSUMES A NEGATIVE TILT. THE
GUIDANCE ALL HAVE THIS FORECAST SCENARIO OF A CLASSIC COASTAL
WINTER STORM BUT STILL DIFFER ON SOME OF THE IMPORTANT DETAILS...
MAINLY THE CRITICAL THERMAL PROFILES AND IF THE TREMENDOUS
ATLANTIC INFLOW HAS AN IMPACT OR NOT ON THE RAIN/SNOW LINE. LIKE
THE LAST FEW NIGHTS... WPC STAYED VERY CLOSE TO A BLEND/COMPROMISE
OF THE GFS/ECMWF AND SREF MEAN ON SYNOPTIC SCALE FEATURES BUT
CLOSER TO THE ECMWF/SREF MEAN FOR THERMAL PROFILES... AS THE GFS
APPEARS TO CONTAIN SOME FEEDBACK ALONG THE IMMEDIATE COASTLINE
THAT IS NOT ONLY IMPACTING THERMALS BUT KEEPING QPF AMOUNTS LOWER
OVER THE MID-ATL REGION. THUS WPC STILL EXPECTS A HEALTHY AXIS OF
HEAVY DEFORMATION/DYNAMIC COOLING SNOWFALL JUST WEST OF I95 OR
MORE SNOW FOR DC/BALT UP THROUGH ERN PA INTO INTERIOR NEW ENGLAND.

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stormtracker

stormtracker

Posted
  • Author
Posted

Hot off the press:

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION

NWS WEATHER PREDICTION CENTER COLLEGE PARK MD

432 AM EST WED FEB 12 2014

VALID 12Z WED FEB 12 2014 - 12Z SAT FEB 15 2014

....

THIS LOW WILL INTENSIFY RAPIDLY

AND TRACK NORTHEASTWARD UP ALONG THE MID ATLANTIC/NORTHEAST

COAST... AS THE PHASED TROUGH ASSUMES A NEGATIVE TILT. THE

GUIDANCE ALL HAVE THIS FORECAST SCENARIO OF A CLASSIC COASTAL

WINTER STORM BUT STILL DIFFER ON SOME OF THE IMPORTANT DETAILS...

MAINLY THE CRITICAL THERMAL PROFILES AND IF THE TREMENDOUS

ATLANTIC INFLOW HAS AN IMPACT OR NOT ON THE RAIN/SNOW LINE. LIKE

THE LAST FEW NIGHTS... WPC STAYED VERY CLOSE TO A BLEND/COMPROMISE

OF THE GFS/ECMWF AND SREF MEAN ON SYNOPTIC SCALE FEATURES BUT

CLOSER TO THE ECMWF/SREF MEAN FOR THERMAL PROFILES... AS THE GFS

APPEARS TO CONTAIN SOME FEEDBACK ALONG THE IMMEDIATE COASTLINE

THAT IS NOT ONLY IMPACTING THERMALS BUT KEEPING QPF AMOUNTS LOWER

OVER THE MID-ATL REGION. THUS WPC STILL EXPECTS A HEALTHY AXIS OF

HEAVY DEFORMATION/DYNAMIC COOLING SNOWFALL JUST WEST OF I95 OR

MORE SNOW FOR DC/BALT UP THROUGH ERN PA INTO INTERIOR NEW ENGLAND.

looks like vinyl and others arguing this last night were right after all.

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