FXUS61 KLWX 030900
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
400 AM EST THU DEC 3 2009
.SYNOPSIS...
DEEP LOW PRESSURE OVER LAKE ERIE WILL TRACK NORTHEAST TO NEW ENGLAND
TODAY. ATMOSPHERIC PRESSURE BUILDS NOW THROUGH FRIDAY NIGHT. A
COASTAL LOW DEVELOPS OFF THE CAROLINAS SATURDAY BEFORE TRACKING
NORTHEAST OFF THE MID ATLANTIC COAST SATURDAY NIGHT. HIGH PRESSURE
WILL RETURN FOR SUNDAY AND MONDAY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
08Z REG SURFACE OBS PUTS THE 988 MB LOW CENTER OVER LAKE
ERIE...THOUGH HERE AT KIAD WE HAVE 995 MB...QUITE THE BROAD SYSTEM.
DRY SLOT HAS PUNCHED INTO WRN HALF OF THE CWA PER WV BAND /KCHO
REPORTING ONLY MID LEVEL CLOUDS ATTM/. THUS...SHOWERS TO CONTINUE TO
LIFT OUT OF THE CWA OVER THE NEXT COUPLE HOURS. WRAP AROUND SWLY
WINDS THE LINGERING CONCERN WITH THIS SYSTEM. 25 TO 30 KT FROM THE
NC PIEDMONT TO SOUTHERN APPALACHIANS WILL SHIFT NORTH ACROSS THE CWA
THROUGH THE MORNING HOURS...THEN SLACKEN TO 15 TO 20 KT FOR THE
AFTERNOON HOURS AS THE GRADIENT WEAKENS.
UPSLOPE RAIN BEGINS THIS MORNING /ECHOES CURRENTLY OVER SRN WV AND
WRN KY TO MOVE TOWARD THE ALLEGHENY FRONT/. COLD AIR JUST ENTERING
OH SPREADS EAST THROUGH THE DAY UNDER THE UPPER TROUGH. HIGHEST
ELEVATIONS ALONG WESTERN SLOPES OF ALLEGHENY FRONT TO SEE SNOW
FLAKES THIS AFTERNOON MIX IN. ACCUMULATING SNOW TO WAIT UNTIL THIS
EVENING WHEN THE CHANGEOVER TO SNOW COMPLETES.
DOWNSLOPING FLOW AND BREAKS AS CLOUDS TRANSITION TO WAVE CLOUDS FROM
THE WESTERN RIDGES TO WARM AREA A BIT DESPITE CRASHING
DEWPOINTS...UPPER 50S INLAND EAST OF THE BLUE RIDGE AND LOW 60S NEAR
SHORE TODAY /MID TO UPPER 50S FOR WRN VALLEYS/.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
TONIGHT...UPSLOPE SNOW FOR ALLEGHENY FRONT...AROUND AN INCH OF
ACCUMULATION. TIMING OF SNOW CHANGEOVER AND MOISTURE AVAILABILITY
KEYS TO WHETHER TWO INCHES /AND A WINTER WX ADVISORY/ IS POSSIBLE.
THINKING TRANSITION WILL BE THIS EVENING AND INTENSITY TO DROP OFF
THROUGH THE NIGHT...SO NO ADVISORY AT THIS TIME.
EAST OF THE ALLEGHENY FRONT...WHETHER THE BALT-DC METRO AREAS REACH
32F DEPENDS ON MIXING AND HIGH CLOUD COVER...THINKING MID 30S ATTM.
FRIDAY...HIGH PRESSURE BUILDING IN. HOWEVER...MOSTLY SUNNY MORNING
GIVES WAY MID/HIGH CLOUD COVER AS PRECURSOR TO COASTAL DEVELOPMENT
OFF CAROLINAS FOR SATURDAY BUILDS NWARD BY FRIDAY AFTERNOON/EVENING.
UPPER 40S TO NEAR 50F MAXT.
UPSLOPE SNOW TAPERS OFF COMPLETELY FRIDAY MORNING.
&&
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
NOT MANY CHANGES TO THE LONG TERM FORECAST MADE. POPULATED WITH NEW
WIND/MAX AND MIN T GRIDS FOR FRIDAY NIGHT INTO SATURDAY.
RIDGE OF HIGH PRESSURE ACROSS THE CWFA WILL SHIFT SLIGHTLY TO THE
NORTH EARLY SATURDAY AS A COASTAL LOW PRESSURE SYSTEM EMERGES OFF
THE SOUTHEAST US COAST. THE LOW CENTER IS EXPECTED TO MOVE UP THE
MIDDLE ATLANTIC COAST THROUGH SUNDAY. HIGH PRESSURE BUILDS IN LATE
SUNDAY AND REMAINS ACROSS THE AREA THROUGH TUESDAY. THE NEXT
FRONTAL/LOW PRESSURE SYSTEM IS EXPECTED FOR MID WEEK.
TEMPERATURES FOR SATURDAY ARE NOT EXPECTED TO RISE MUCH OUT OF THE
30S FOR MOST LOCALES...WITH LOWER SOUTHERN MARYLAND IN THE LOWER
40S. SNOW SHOWERS ARE EXPECTED IN THE HIGHER ELEVATIONS...WITH A
RAIN/SNOW MIX MOST EVERYWHERE ELSE. LOWER SOUTHERN MARYLAND MAY STAY
WARM ENOUGH FOR ALL RAIN.
&&
.AVIATION /09Z THURSDAY THROUGH MONDAY/...
LAST ROUND OF GUSTY CONVECTIVE SHOWERS /WINDS 25 TO 30 KT/ TO MOVE
THROUGH BALT-DC METRO AREAS THROUGH 5 AM OR SO.
STRONG SWLY WINDS WITH GUSTS 25 TO 30 KT BEHIND FROPA THROUGH MIDDAY
BEFORE DIMINISHING AS GRADIENT SLACKENS AND WINDS TURN WLY THIS
AFTERNOON.
SUB VFR CONDITIONS EXPECTED ON SATURDAY AS A LOW PRESSURE CENTER
MOVES UP THE EAST COAST. NO VSBY/CIG RESTRICTIONS EXPECTED FROM
SUNDAY THROUGH TUESDAY.
&&
.MARINE...
LAST ROUND OF CONVECTIVE SHOWERS TO MOVE THROUGH DC AND NORTH OF
DRUM POINT BEFORE SUNRISE.
DROPPED GALE WARNING PER OBS SWLY 25 TO 30 KT OUTSIDE OF CONVECTIVE
GUSTS. STRONG SCA CONDITIONS THROUGH THE AFTERNOON BEFORE THE
GRADIENT BEGINS TO SLACKEN...SCA NOW UP THROUGH TONIGHT /ALL ZONES
TONIGHT EXCEPT UPPER TIDAL POTOMAC AND PATAPSCO/ WITH NLY CHANNELING
POSSIBLE LATE TONIGHT MAINTAINING THREAT TO MARINE INTERESTS.
NWLY WINDS CONTINUE FRIDAY...10 TO 15 KT...BEFORE A COASTAL SYSTEM
DEVELOPS OFF THE CAROLINAS ON SATURDAY.
SMALL CRAFT CONDITIONS ARE POSSIBLE SATURDAY AND SUNDAY AS A LOW
PRESSURE SYSTEM MOVES UP THE EASTERN SEABOARD.
&&
.TIDES/COASTAL FLOODING...
POSITIVE DEPARTURES UP TO 1.5 FEET DECREASE TODAY AS WINDS BECOMES WESTERLY.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EST FRIDAY FOR ANZ530>534-537-
539>543.
SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS EVENING FOR ANZ535-
536-538.
&&
$$
BAJ/LISTEMAA
