FXUS61 KLWX 300159
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
859 PM EST SUN NOV 29 2009
.SYNOPSIS...
HIGH PRESSURE WILL MOVE OFF THE EASTERN SEABOARD TONIGHT. A COLD
FRONT WILL MOVE ACROSS THE REGION ON MONDAY WITH SHOWERS. HIGH
PRESSURE RETURNS TUESDAY...BUT LOW PRESSURE WILL IMPACT THE REGION
WEDNESDAY INTO THURSDAY. CANADIAN HIGH PRESSURE WILL BUILD
OVERHEAD LATE IN THE WEEK.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
COLD FRONT WILL WAIT TIL MON...BUT SOME WAVES OF SHOWERS WILL
PROCEED IN THE FLOW AHEAD OF THE FROPA. A FEW SHOWERS IN EAST
CENTRAL VA MAY SKIRT THE LOWER POTOMAC...CENTRAL BAY...AND LOWER S
MD BETWEEN 10 AND 11PM. ALSO A BAND OF SHOWERS IS MOVING IN ON
WESTERN MD AND EASTERN WV AND SHOULD REACH THE E CONTINENTAL
DIVIDE AROUND 10PM. IT IS LIKELY TO WEAKEN A BIT AS IT GETS E OF
THE MTNS. OTHER THAN THOSE TWO AREAS TO FOLLOW...DONT SEE A LOT
AFFECTING US RAINWISE THRU THE NIGHT. HAVE ADJUSTED ALL GRIDS
ACCORDINGLY AND TO CURRENT TRENDS. WINDS BEGINNING TO TOUCH SMALL
CRAFT VALS ON THE BAY.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
BY THE PRE-DAWN HRS MON...RAIN SHOWERS ARE EXPECTED TO BE PUSHING
INTO THE POTOMAC HIGHLANDS AND THE ALLEGHENY FRONT. A WEAK
PRE-FRONTAL BAND WELL AHEAD OF THE MAIN AREA OF SHOWERS...MAY MOVE
THRU EARLY /11-14Z/ THOUGH THIS MAY END UP SCATTERING OUT AS IT
MOVES INTO THE PIEDMONT. BY MID MORNING...A FAIRLY SOLID BAND OF
RAIN SHOWERS WILL LIKELY BE PUSHING THRU THE AREA...INTO THE LATE
MRNG AND EARLY AFTERNOON ACROSS THE ERN ZONES. BY MID AFTN...A BIT
OF REDEVELOPMENT AND SLIGHTLY HIGHER QPFS FOR LOCALES NEAR THE BAY
W/ A BETTER SLY MOISTURE SURGE AND INCREASED FORCING AS THE BASE OF
THE UPPER TROF PUSHES INTO THE APLCNS AND HELPS STRENGTHEN THE LOW
LEVEL WAA AREA JUST OFFSHORE.
OVERALL THE QPF FOR THE MID ATLC REGION WILL BE LIGHT W/ THIS
ACTIVITY...ESPECIALLY W/ A NE TO SW ORIENTED FRONT AND WEAK FORCING
AND SFC MOISTURE CONVERGENCE. WITH THE CLOUDS AND PRECIP...TEMPS
WILL BE MODERATED NOT ONLY FROM THE OVERNIGHT LOWS ONLY INTO THE 40S
TONIGHT...SO HIGHS WILL PEAK INTO THE 50S ON MON AFTN.
&&
.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
COLD FRONT AND ITS ASSOCIATED SHOWERS RAPIDLY MOVE OFF THE COAST
EARLY MONDAY EVENING...ALLOWING FOR MUCH OF THE CWA TO DRY OUT.
EXCEPTION WILL BE ACROSS THE HIGHLANDS WHERE AN UPSLOPE COMPONENT
WILL ALLOW PRECIPITATION CHANCES TO LINGER. COLDER TEMPERATURES WILL
MEAN A CHANGEOVER TO SNOW SHOWERS...AND THE MOST LIKELY TIME FRAME
FOR LIGHT UPSLOPE ACCUMULATIONS ALONG FAVORED SLOPES LOOKS TO BE
FROM 06Z TO 12Z TUESDAY.
SURFACE HIGH PRESSURE BUILDS ACROSS THE MID ATLANTIC AND SOUTHEAST
STATES ON TUESDAY...THEN MOVES OFF THE COAST TUESDAY NIGHT INTO
EARLY WEDNESDAY.
AS HAS BEEN ADVERTISED FOR DAYS...NEW LOW PRESSURE DEVELOPS IN THE
GULF OF MEXICO ALONG THE TAIL END OF THE FRONT THAT MOVES THROUGH
THE CWA MONDAY. LOW PRESSURE IS FORECAST TO TRACK NORTHWARD INTO THE
MID ATLANTIC DURING THE MID WEEK. MODELS ARE CONVERGING ON A MORE
INLAND SOLUTION WITH LOW PRESSURE TRACKING UP THE APPALACHIANS.
REGARDLESS OF THE EXACT TRACK...LOW PRESSURE WILL BRING A RAIN EVENT
TO THE CWA. CLOUDS WILL THICKEN UP WEDNESDAY...AND RAIN WILL START
TO BREAK OUT IN THE AFTERNOON ACROSS THE SOUTHERN PORTION OF THE
CWA. RAIN WILL THEN EXPAND NORTH TO INFILTRATE THE REMAINDER OF THE
CWA DURING THE EVENING HOURS. CATEGORICAL POPS RESIDE ACROSS ENTIRE
CWA WEDNESDAY NIGHT. RAINFALL TOTAL AOA AN INCH MAY RESULT. IN
ADDITION...WITH A SLIGHTLY SLOWER EXODUS OF THE LOW/RAIN...POPS HAVE
BEEN INCREASED ON THURSDAY MORNING BEFORE A DRY SLOT WOULD LIKELY
WORK INTO THE CWA.
IN THE WAKE OF LOW PRESSURE...ANOTHER ROUND OF UPSLOPE SNOW SHOWERS
CAN BE EXPECTED THURSDAY NIGHT INTO FRIDAY. EAST OF THE MTNS SHOULD
BE DRY...BUT PRESENCE OF AN UPPER TROUGH WILL LIKELY KEEP SOME
CLOUDS AROUND. HIGH PRESSURE IS FORECAST TO BUILD BACK ON SATURDAY.
&&
.AVIATION /02Z MONDAY THROUGH FRIDAY/...
VFR CONDITIONS THRU EARLY MON. NO WX CONCERNS OVERNIGHT...ONLY
MID-UPPER CLOUD DECKS STREAMING IN FROM THE WEST. S-SWLY WINDS WILL
REMAIN LIGHT /5-10KT/ ACROSS THE MID ATLC...A THO A FEW LOCALES WILL
INTERMITTENTLY GUST NEAR 15KT. EARLY MONDAY MORN...CIGS WILL DROP TO
NEAR MVFR AND BY MID MORNING...SCATTERED RAIN SHOWERS AND HI-END
MVFR CIGS /2-3KFT/ WILL BE COMMON THRU AT LEAST EARLY AFTN. BY
MID-LATE AFTN...MUCH OF THE ACTIVITY WILL BE PUSHING INTO THE
CHESAPEAKE BAY REGION AND EVENTUALLY OFF THE COAST INTO THE
EVENING HRS. SFC WINDS WILL STRENGTHEN AFTER THE COLD FRONT MOVES
THRU /MID-LATE AFTN/ AND PICK UP FROM THE NW INTO 15-20KT RANGE.
NORTHWEST WINDS SETTLE IN BEHIND A COLD FRONT MONDAY NIGHT INTO
TUESDAY. HIGH PRESSURE TUESDAY MOVES OFF THE COAST TUESDAY NIGHT
INTO WEDNESDAY. LOW PRESSURE NEAR THE GULF COAST WILL LIFT NORTH
INTO THE MID ATLANTIC WEDNESDAY NIGHT/THURSDAY. RAIN ASSOCIATED WITH
LOW PRESSURE MAY LEAD TO IFR CONDITIONS WEDNESDAY NIGHT/THURSDAY.
&&
.MARINE...
A COLD FRONT WILL CROSS THE WATERS ON MONDAY AFTN/EVENING. THE SFC
PRESSURE GRADIENT WELL AHEAD OF THE FRONT...HAS BEGUN TO
STRENGTHEN OVER THE BAY. SCA CONDITIONS ARE EXPECTED FOR THE
MIDDLE/LOWER PORTIONS OF THE BAY STARTING AROUND 9PM AND LASTING
THRU MUCH OF THE OVERNIGHT HRS. BY THE PRE- DAWN HRS MONDAY...WINDS
WILL WEAKEN A BIT FOR MUCH OF THE BAY /EXCEPT THE LOWER MD
BAY/...THEN PICK-UP AGAIN TOWARD LATE AFTN AND EARLY EVENING
BEHIND THE COLD FRONT.
NORTHWEST WINDS WILL LIKELY BE IN SMALL CRAFT ADVISORY RANGE ACROSS
MUCH OF THE WATERS MONDAY NIGHT...POSSIBLY LASTING INTO TUESDAY.
WINDS SHOULD RELAX TUESDAY NIGHT INTO WEDNESDAY...BUT LOOK TO PICK
BACK UP WEDNESDAY NIGHT INTO THURSDAY AS LOW PRESSURE MOVES ACROSS
THE AREA.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EST MONDAY FOR ANZ531>533-
539>542.
SMALL CRAFT ADVISORY FROM 6 PM MONDAY TO 6 PM EST TUESDAY FOR
ANZ530>533-538>542.
SMALL CRAFT ADVISORY UNTIL 6 PM EST TUESDAY FOR ANZ534-537-543.
&&
$$
SYNOPSIS...BPP/GMS
NEAR TERM...CS
SHORT TERM...GMS
LONG TERM...BPP
AVIATION...BPP/GMS/CS
MARINE...BPP/GMS/CS
