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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KLWX 100955
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
455 AM EST WED FEB 10 2010

.SYNOPSIS...
LOW PRESSURE WILL MOVE OFF OF THE COAST OF THE CAROLINAS TODAY AND
THEN UP THE EASTERN SEABOARD OVERNIGHT AND THURSDAY. THIS LOW
PRESSURE SYSTEM WILL BRING ANOTHER ROUND OF WINTRY PRECIPITATION TO
THE AREA...ALONG WITH GUSTY WINDS. HIGH PRESSURE WILL BUILD OVER THE
AREA FOR THE LATTER HALF OF THE WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --
QUICK UPDATE TO THE ZONES TO BUMP DOWN THE TOTAL SNOWFALL AMOUNTS
ACROSS PORTIONS OF THE CWFA...ESPECIALLY THOSE AREAS THAT
EXPERIENCED A LONG BREAK IN THE SNOW AND THOSE AREAS THAT HAVE
RECEIVED A WINTRY MIX OVERNIGHT. PRODUCTS OUT SHORTLY.


THE BIGGEST CHANGE FOR THIS UPDATE IS AN UPGRADE TO BLIZZARD WARNING
FOR THE PORTIONS OF THE CWA...STARTING LATE MORNING THRU THE AFTN.
AREAS AFFECTED EXPECTED TO BE EXTREME NERN MD...ALONG THE
MASON-DIXON LINE /AND ESPECIALLY HIGHER TERRAIN ACROSS THE WRN ZONES
LIKE THE CATOCTINS AND POTOMAC HIGHLANDS/ AND ACROSS THE HIGHER
ELEVATIONS OF THE ALLEGHENY MTNS. THE TRUE DYNAMICS OF THIS SYSTEM
WILL GEAR-UP IN THE COMING HRS THIS MORNING...AS THE UPPER LOW
SHOOTS SEWD ACROSS THE CWA AND THE COASTAL LOW QUICKLY DEEPENS JUST
OFF THE DELMARVA COAST.

EARLY INDICATIONS OF WHAT/S IN STORE AS THESE ELEMENTS COME TOGETHER
OVER THE AREA CAN BE SEEN ON REGIONAL RADAR...W/ A SFC TROF THAT IS
QUICKLY SLIDING THRU WV...NOW CROSSING THE CNTRL APLCNS AND WILL
SHORTLY BE MOVING INTO THE I-81 CORRIDOR. WIND GUSTS OF 25-35KT
COMMON W/ THE PASSAGE...ALONG W/ ABOUT A 10-15 DEGREE TEMPERATURE
DROP AND A DECENT PRESSURE SURGE ASSOCIATED W/ THE FEATURE. AS THIS
FEATURE TRUDGES ACROSS THE FOOTHILLS AND PIEDMONT LATER INTO THE
PRE-DAWN HRS...THE LOW LEVEL WAA LAYER THAT GAVE PARTS OF THE REGION
A MIXED PRECIP REGIME OVERNIGHT WILL QUICKLY BE REPLACED W/ A COLD
AIRMASS AND DRIER AIR WILL ALSO MIX-DOWN...BUT MAINLY DOWN INTO
CNTRL-SRN VA.

CURRENTLY...SCATTERED AREAS OF LIGHT-MODERATE SNOW FILLING-IN OVER
MUCH OF THE CWA BEHIND THE HEAVIER ACTIVITY FROM LATE LAST
NIGHT...THAT HAS SINCE MOVED UP INTO NJ/SRN NY. BETWEEN THE
APPROACHING UPPER LOW AND THE DEEPENING COASTAL LOW WILL BE AN AXIS
OF HIGHER MOISTURE INFLUX AND LIFT...LEADING TO BANDING OF SNOW
ACROSS THE I-95 CORRIDOR OF NRN VA-ERN MD LATER THIS MORNING. ONCE
THIS FEATURE SETS-UP...PERIODS OF HEAVY SNOW AND NEAR WHITE-OUT
CONDITIONS WILL DEVELOP /ESPECIALLY ACROSS NERD MD/. HEAVIER
SNOWFALL RATES AND STRONGER WINDS WILL BEGIN TO OVERSPREAD THESE
AREAS...AND BLIZZARD CONDITIONS WILL BECOME MORE LIKELY FROM LATE
MORNING INTO THE EARLY AFTN HRS.

THE SNOW BAND WILL BEGIN TO MOVE EWD TOWARD DELMARVA INTO THE MID
AFTN HRS...AND MUCH OF THE SNOW WILL START TO TAPER OFF ACROSS THE
CWA THRU THE LATE AFTN AND EARLY EVENING HRS. A STRONG LOW LEVEL
JET WILL BE ORIENTED OVER THE AREA FOR MUCH OF THE DAY /50-60KT AT
850MB/...HELPING TO MIX-DOWN STRONGER GUSTS AND DISSIPATE PRECIP
FASTER BEHIND THE EXITING SYSTEM. WIND GUSTS OF 30-45 MPH WILL BE
COMMON ACROSS THE REGION...BLOWING AND DRIFTING NEWLY FALLEN SNOW.
THE BLIZZARD WARNING AREAS ARE MOST COINCIDENT W/ AREAS THAT ARE
EXPECTED TO EXPERIENCE THE NEAR WHITE-OUT CONDITIONS FROM THE
STRONGEST WINDS AND HEAVIEST SNOWFALL/BLOWING SNOW AT THE SAME TIME
/CENTERED MAINLY AROUND THE LATE MORNING-EARLY AFTN/.
ELSEWHERE...SNOW MAY TAPER OFF BEFORE THE HIGHEST WINDS MOVE ACROSS
THE AREA.
-- End Changed Discussion --

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/...
UPSLOPE SNOW WILL CONTINUE FOR THE CNTRL APLCNS WELL AFTER THE
COASTAL LOW HAS MOVED OFF THE MID ATLC COAST THRU THURSDAY AFTN.
MODERATE SNOW ACCUMULATION POSSIBLE FOR THE HIGHER ELEVATIONS DURING
THIS PERIOD. E OF THE MTNS...DRY-COLD AND WINDY WX WILL REPLACE THE
EXITING LOW PRESSURE SYSTEM.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
NO MAJOR CHANGES TO THE LONG TERM PORTION OF THE FORECAST WERE MADE.

UPSLOPE SNOW SHOWERS WILL BEGIN TO WANE ON THURSDAY AS HIGH PRESSURE
BUILDS IN FROM THE WEST. HAVE KEPT POPS PRETTY HIGH ACROSS THE
WESTERN RIDGES...BUT SNOW SHOULD COMPLETELY CUT OFF BY EARLY FRIDAY.
TEMPERATURES ARE EXPECTED TO REMAIN BLO FREEZING FOR MOST LOCALES
THURSDAY AND THURSDAY NIGHT...BUT ABOVE FREEZING MAX TEMPS ARE
EXPECTED FRIDAY AND SATURDAY. A COLD FRONT COMES THROUGH THE REGION
DURING THE WEEKEND...WITH HIGH PRESSURE BUILDING IN FOR THE FIRST
PART OF NEXT WEEK.

&&

.AVIATION /10Z WEDNESDAY THROUGH SUNDAY/...
A BRIEF LULL IN THE ACTIVITY OVERNIGHT FOR THE REGION /THO ONLY A
RELATIVE LULL...AS MOST AREAS REPORTING AT LEAST LIGHT FROZEN PRECIP
AND VERY LOW CIGS AND MODERATELY LOW VSBYS. A LARGE BAND OF MODERATE
TO HEAVY SNOW WILL SET-UP OVER THE DC-BALT METRO AREA /ESPECIALLY
THE BALT METRO AREA/ LATER THIS MORNING...AS WINDS ALSO INCREASE OUT
OF THE WNW. STRONG WINDS AT THE SFC AND ALOFT EXPECTED TOWARD THE
NOON HR...AND LASTING FOR THE NEXT 24-36 HRS. GUSTS NEAR 40KT WILL
BE COMMON THROUGHOUT THE AFTN/EVENING...SUBSIDING ONLY A BIT
OVERNIGHT AND LASTING INTO THU. IFR/LOWER EXPECTED ACROSS THE REGION
FOR THE NEXT SEVERAL HRS...AS SFC CONDITIONS REMAIN MOIST AND PRECIP
/MAINLY SNOW-SOME OF THE A MIX ALSO POSSIBLE/ LINGERS JUST AHEAD OF
THE STRONG WINDS. ONCE THE WINDS MIX-IN LATER THIS AFTN...DRIER
CONDITIONS WILL CLEAR-OUT MUCH OF THE SFC MOISTURE AND DENSE OVC BY
LATER THIS EVENING...BUT AS MENTIONED WINDS AT THE SFC AND THRU THE
LOWEST FEW THOU FT WILL BE FAIRLY STRONG.

CIGS/VSBYS ARE EXPECTED TO REMAIN VFR THROUGH THURSDAY AT MOST
LOCALES. HOWEVER...BLOWING SNOW MAY LOCALLY REDUCE SOME VSBYS BLO
VFR AT TIMES WHERE WINDS ARE THE MOST GUSTY. HIGH PRESSURE BUILDS IN
FOR THE REMAINDER OF THE WEEK AND NO CIGS/VSBY RESTRICTIONS ARE
ANTICIPATED.

&&

.MARINE...
LIGHT WINDS ON THE WATERS CURRENTLY...BUT THIS WILL QUICKLY BE
REPLACED W/ GALE CONDITIONS BY LATER THIS MORNING. A STRONG LOW
PRESSURE SYSTEM AFFECTING THE REGION WILL INCREASE WINDS OVER THE
WATERS TODAY...WELL INTO THE OVERNIGHT HRS AND INTO THU.

GALE CONDITIONS ARE EXPECTED TO CONTINUE THROUGH MOST OF THURSDAY AS
LOW PRESSURE MOVES UP THE EASTERN SEABOARD. THE GRADIENT IS EXPECTED
TO LESSEN THURSDAY EVENING AND OVERNIGHT AS HIGH PRESSURE BUILDS IN
FROM THE WEST. HOWEVER...SMALL CRAFT CONDITIONS ARE LIKELY THROUGH
THIS PERIOD. TO LESSEN CONFUSION...WILL NOT TACK ON THE SCA HEADLINE
ON THE END OF THE GALE. WILL MENTION IN THE SYNOPSIS AND HAVE 20
PLUS KT IN THE TEXT.

HIGH PRESSURE BUILDS IN FOR THE LATTER PART OF THE WEEK...AND
LIGHTER WINDS ARE EXPECTED.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...WINTER STORM WARNING UNTIL 7 PM EST THIS EVENING FOR DCZ001.
MD...WINTER STORM WARNING UNTIL 7 PM EST THIS EVENING FOR MDZ009-
     013-016>018.
     WINTER STORM WARNING UNTIL 10 AM EST THIS MORNING FOR
     MDZ003>007-010-011-014-502.
     BLIZZARD WARNING FROM 10 AM THIS MORNING TO 7 PM EST THIS
     EVENING FOR MDZ003>007-010-011-014.
     BLIZZARD WARNING FROM 10 AM THIS MORNING TO 4 PM EST THIS
     AFTERNOON FOR MDZ502.
     BLIZZARD WARNING UNTIL 7 AM EST THURSDAY FOR MDZ501.
VA...WINTER STORM WARNING UNTIL 7 PM EST THIS EVENING FOR VAZ030-
     031-040-042-050>057-501-502.
     WINTER STORM WARNING UNTIL 4 PM EST THIS AFTERNOON FOR
     VAZ025>029-036>039.
     BLIZZARD WARNING UNTIL 7 AM EST THURSDAY FOR VAZ021.
WV...WINTER STORM WARNING UNTIL 7 PM EST THIS EVENING FOR WVZ052-
     053.
     WINTER STORM WARNING UNTIL 10 AM EST THIS MORNING FOR WVZ050-
     051-055-502-504.
     BLIZZARD WARNING FROM 10 AM THIS MORNING TO 4 PM EST THIS
     AFTERNOON FOR WVZ050-051-055-502-504.
     BLIZZARD WARNING UNTIL 7 AM EST THURSDAY FOR WVZ054-501-503.
MARINE...GALE WARNING UNTIL 6 PM EST THURSDAY FOR ANZ530>543.

&&

$$