FXUS61 KLWX 020849
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
349 AM EST WED DEC 2 2009

.SYNOPSIS...
AN INTENSIFYING LOW PRESSURE SYSTEM WILL TRACK FROM THE WESTERN GULF 
COAST THROUGH THE TENNESSEE VALLEY TODAY...BEFORE MOVING THROUGH THE 
OHIO VALLEY AND INTO UPSTATE NEW YORK TONIGHT. HIGH PRESSURE BUILDS 
IN THURSDAY NIGHT AND FRIDAY. A COASTAL DISTURBANCE DEVELOPS OFF THE 
CAROLINAS SATURDAY. HIGH PRESSURE TO RETURN FOR SUNDAY AND MONDAY.
&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
SURFACE HIGH PRESSURE HAS MOVED OFF INTO THE WESTERN ATLANTIC THIS 
MORNING. LOW PRESSURE HAS FORMED ALONG THE GULF COAST...AND WILL 
MOVE NORTHEAST DURING THE DAY TODAY. THE RAIN SHIELD ASSOCIATED WITH 
THE LOW PRESSURE CENTER HAS BEGUN TO OVERSPREAD THE CAROLINAS AND IS 
APPROACHING SOUTHERN VIRGINIA EARLY THIS MORNING. 

THICK CIRRUS HAS MOVED NORTH IN ADVANCE OF THE LOWER CLOUDS AND 
PRECIPITATION THIS MORNING...HELPING KEEP TEMPERATURES IN THE MIDDLE 
30S TO MIDDLE 40S ACROSS THE CWFA...SOME 5 TO 10 DEGREES WARMER THAN 
LAST NIGHTS READINGS. CLOUDS WILL CONTINUE TO THICKEN THIS 
MORNING...AND CIGS WILL LOWER. RAIN SHOULD BE ON THE DOORSTEP IN THE 
SW CWFA BY 12Z THIS MORNING...AND WILL CONTINUE TO SPREAD NE DURING 
THE DAY. TRIED TO TIME THE ONSET OF PRECIP EARLY THIS MORNING...BUT 
JUST WENT CATEGORICAL FOR THE REMAINDER OF THE AFTERNOON. RAINFALL 
COULD BECOME MODERATE AT TIMES ACROSS THE CENTRAL FOOTHILLS OF 
VIRGINIA BY THE LATE AFTERNOON. 

AHEAD OF THE SURFACE LOW...WINDS ALOFT WILL BEGIN TO STRENGTHEN. SE 
WINDS SUSTAINED OF AROUND 25 TO 30 KT...WITH GUSTS TO 40 KT ARE 
POSSIBLE ACROSS THE HIGHER TERRAIN. HAVE HOISTED A WIND ADVISORY FOR 
THE POTOMAC HIGHLANDS...AND ALONG SKYLINE DRIVE BEGINNING AT 10 AM 
AND GOING THROUGH THE EVENING.
&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/...
THE LOW PRESSURE SYSTEM WILL MOVE INTO THE OHIO VALLEY 
OVERNIGHT...PUSHING A FRONT THROUGH THE CWFA AFTER 06Z. WINDS ARE 
EXPECTED TO SHIFT AROUND TO THE WEST TOWARDS SUNRISE. THE HIGHER 
WINDS ALOFT WILL ALSO SHIFT TO THE NE OVERNIGHT...AND HAVE EXPIRED 
THE WIND ADVISORY AT 10 PM...AGAIN THE HIGHEST WINDS ARE EXPECTED IN 
THE HIGHER TERRAIN. 

MODELS HAVE CONTINUED TO PRODUCE SOME INSTABILITY ALONG THE FRONT 
OVERNIGHT. HAVE KEPT THE MENTION OF THUNDER OVERNIGHT FOR AREAS 
ALONG AND EAST OF THE BLUE RIDGE. WITH STRONG WINDS ALOFT...EVEN 
SHOWERS (AND DEFINITELY ANY THUNDERSTORMS) COULD PRODUCE SOME HIGHER 
WIND GUSTS IN THE LOWER ELEVATIONS.
&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
THURSDAY MORNING...LOW CENTER OVER UPSTATE NY AND QUICKLY MOVING NE. 
ANY LINGERING SHOWERS TO CLEAR THE BAY BY MID MORNING /IF NOT 
EARLIER/ AS DRYSLOT/DOWNSLOPING CUTS OFF PRECIP. UPSLOPE PRECIP 
PERIOD BEGINNING OUT WEST AS FLOW BECOMES WLY. DENSE PRESSURE 
GRADIENT CONTINUES THROUGH THURSDAY WITH WINDS 25 TO 30 MPH  
EXPECTED THROUGH THE AFTERNOON /35 MPH GUSTS ACROSS THE ENTIRE CWA 
THURSDAY MORNING NOT OUT OF THE QUESTION/.

LATER THURSDAY THROUGH FRIDAY. OUT WEST...UPSLOPE RAIN FOR THE 
ALLEGHENY FRONT THROUGH THE AFTERNOON HOURS BEFORE A CHANGEOVER TO 
SNOW IN THE EVENING. ACCUMULATION BEGINS BY MIDNIGHT. UP TO A COUPLE 
INCHES OF SNOWFALL EXPECTED FOR PRIME UPSLOPE LOCALES AT THIS TIME 
AS GUIDANCE CONTINUES TO INDICATE WINDS SOUTH OF WEST AFTER SUNRISE 
FRIDAY...CUTTING OFF GREAT LAKES MOISTURE SOURCE.

EAST OF THE ALLEGHENY FRONT...PARTLY CLOUDY CONDITIONS IN 
DOWNLSOPING FLOW ALLOWS TEMPERATURES TO DROP TO AROUND 30F FOR THE 
WESTERN VALLEYS AND LOW TO MID 30S EAST OF THE BLUE RIDGE /40F NEAR 
SHORE/. THE JET STREAM INTENSIFIES OVERHEAD FRIDAY...EXPECT HIGH/MID 
CLOUD COVER TO THICKEN THROUGH THE DAY LIMITING TEMPERATURES TO THE 
UPPER 40S /MID TO UPPER 40S FOR VALLEYS/.

SATURDAY...DEEP CENTRAL CONUS TROUGH ROTATES FROM POSITIVE TILT DOWN 
THE SOUTHERN PLAINS FRIDAY TO A NEGATIVE TILT TO THE SERN CONUS BY 
SATURDAY MORNING. SOME WEAK FRONTOGENESIS ALONG BAROCLINIC ZONE  ON 
APPALACHIAN SPINE /BELOW THE JET/ COULD SQUEEZE OUT SOME SNOW FOR 
BLUE RIDGE AND WEST LATE FRIDAY NIGHT/EARLY SATURDAY MORNING /WENT 
FOR SCHC/. BROAD CYCLOGENESIS OFF THE CAROLINA COAST EXPECTED SAT 
MORNING. SOME AREAS/BANDED PRECIP EXTENDING NORTHWEST INTO THE CWA 
EXPECTED...TEMPERATURES COLD ENOUGH FOR SNOW EXCEPT OVER THE BAY. 
INCLUDED SOME LOW CHANCES FOR SNOW OR RAIN/SNOW MIX...IMPACT 
POTENTIAL LOOKS LOW AT THIS TIME...THOUGH THE SITUATION WILL 
CONTINUE TO BE MONITORED CLOSELY.

SUNDAY AND INTO NEXT WEEK...TROUGH AXIS PUSHES OFF THE COAST 
/PUSHING LOW WELL OUT TO SEA/ AS A RIDGE BUILDS OVER THE ERN CONUS. 
TEMPERATURES SUNDAY/MONDAY AROUND EARLY DECEMBER NORMALS OF UPPER 
40S FOR MAXES AND LOW 30S FOR MINS. THE NEXT DISTURBANCE LOOKS TO BE 
TUESDAY AT THE EARLIEST.
&&

.AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
CONDITIONS REMAIN VFR EARLY THIS MORNING...BUT EXPECT CIGS/VSBYS TO 
BEGIN LOWERING DURING THE MID MORNING FOR KCHO...AND LATE 
MORNING/EARLY AFTERNOON FOR THE REMAINDER OF THE TERMINAL SITES. 
MVFR CIGS/VSBYS WILL BE WIDESPREAD IN RAIN THIS AFTERNOON AND EARLY 
THIS EVENING. VSBYS MAY LOWER TO IFR VALUES WITH THE HEAVIEST RAIN 
DURING THE LATE EVENING AND OVERNIGHT HOURS...WITH THE CHANCE FOR 
THUNDERSTORMS. 

GUSTY SWLY WINDS /25 TO POSSIBLY 30 KT/ THURSDAY MORNING AS FRONT 
PUSHES THROUGH AND LOW PRESSURE CENTER LIFTS THROUGH UPSTATE NEW 
YORK. WINDS BECOME WESTERLY FOR THE AFTERNOON WITH GUSTS 20 TO 25 
KT. HIGH PRESSURE/VFR THEN THROUGH FRIDAY. LATER FRIDAY INTO 
SATURDAY...MID LEVEL CLOUDS THICKEN AND LOW IN ADVANCE OF UPPER 
TROUGH. COULD BE ENOUGH LIFT FOR SNOW /MIX WITH RAIN NEAR SHORE INCL 
DCA/BWI/ ON SATURDAY. HIGH PRESSURE/VFR SUNDAY AND MONDAY.
&&

.MARINE...
LOW PRESSURE WILL MOVE OUT OF THE LOWER MISSISSIPPI RIVER VALLEY 
INTO THE OHIO RIVER VALLEY TODAY AND TONIGHT. THE PRESSURE GRADIENT 
IS EXPECTED TO BEGIN TIGHTENING LATER THIS AFTERNOON...WITH 
SUSTAINED SE WINDS INCREASING...ALONG WITH THE GUST POTENTIAL. GUSTS 
TO 25 KT WILL BECOME MORE LIKELY LATER THIS AFTERNOON. BUFKIT 
SOUNDINGS DO SHOW THE POTENTIAL FOR GUSTS NEAR GALE FORCE OVERNIGHT 
FOR THE LOWER TIDAL POTOMAC AND BAY. WILL GO AHEAD AND ISSUE A GALE 
WARNING FOR THOSE AREAS. 

STRONG LOW PRESSURE SYSTEM LIFTS AWAY FROM THE MID ATLANTIC THURSDAY 
MORNING...ANY LINGERING SHOWERS OVER THE WATERS END MID MORNING. 
STRONG SCA WINDS CONTINUE THROUGH WEDNESDAY MORNING WITH SWLY THEN 
WLY FLOW IN THE WAKE OF THE SYSTEM. SCA EXPECT TO CONTINUE THROUGH 
MOST OF THURSDAY NIGHT. HIGH PRESSURE/MORE TRANQUIL FRIDAY AS CLOUD 
COVER THICKENS. 

A COASTAL LOW DEVELOPS OFF THE CAROLINAS SATURDAY...INTENSITY OF 
WHICH IS YET TO BE SEEN IN GUIDANCE. EXPECT MORE SCA/S OVER THE 
WEEKEND.
&&

.TIDES/COASTAL FLOODING...
WATER LEVELS CONTINUE TO RISE OVERNIGHT...WITH ANOMALIES AROUND A 
FOOT ABOVE PREDICTED VALUES THIS MORNING. CBOFS AND THE 
EXTRATROPICAL MODEL DO KEEP ANY TIDAL ANOMALIES FOR THIS MORNINGS 
EARLY HIGH TIDE (THE LOWER OF THE TWO TODAY) BELOW ANY CRITICAL 
THRESHOLD VALUES. HOWEVER...THE LATE AFTERNOON/EARLY EVENING HIGH 
TIDE MAY APPROACH MINOR COASTAL FLOODING VALUES. WATER LEVELS SHOULD 
REMAIN ABOVE NORMAL VALUES INTO THURSDAY. 

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...WIND ADVISORY FROM 10 AM THIS MORNING TO 10 PM EST THIS 
     EVENING FOR MDZ501.
VA...WIND ADVISORY FROM 10 AM THIS MORNING TO 10 PM EST THIS 
     EVENING FOR VAZ021-025-026-029-030-036>040.
WV...WIND ADVISORY FROM 10 AM THIS MORNING TO 10 PM EST THIS 
     EVENING FOR WVZ054-501-503.
MARINE...SMALL CRAFT ADVISORY FROM 1 PM THIS AFTERNOON TO 6 PM EST THIS 
     EVENING FOR ANZ530>534-537>543.
     SMALL CRAFT ADVISORY FROM 4 AM TO 6 PM EST THURSDAY FOR 
     ANZ530>534-537>543.
     GALE WARNING FROM 6 PM THIS EVENING TO 4 AM EST THURSDAY FOR 
     ANZ530>534-537>543.
     SMALL CRAFT ADVISORY FROM 1 PM THIS AFTERNOON TO 6 PM EST 
     THURSDAY FOR ANZ535-536.

&&

$$
LISTEMAA/BAJ