FXUS61 KLWX 302011
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
311 PM EST MON NOV 30 2009

.SYNOPSIS...
HIGH PRESSURE WILL BUILD IN BEHIND A COLD FRONT TONIGHT...AND LAST
INTO TUESDAY. LOW PRESSURE WILL APPROACH THE MID ATLANTIC ON
WEDNESDAY...AND MOVE THROUGH THE REGION WEDNESDAY NIGHT AND
THURSDAY. HIGH PRESSURE RETURNS ON FRIDAY. 

&&

.NEAR TERM /THROUGH TONIGHT/...
A BRIEF LULL BEHIND THE INITIAL WAVE OF PRECIP HAS BROUGHT...MORE 
PRECIP. MORE WIDESPREAD COVERAGE BULLS-EYED OVER THE N CNTRL VA 
PIEDMONT...A REDEVELOPMENT THAT MODELS SUGGESTED WOULD HAPPEN CLOSER 
TO THE BAY...THO HIGH FORECAST POPS THIS AFTN WERE EXPECTED FROM THE 
SLOW-MOVING RESIDUAL ACTIVITY WELL TO THE WEST OF THE AREA /ACROSS 
CNTRL WV/. BETWEEN THE INITIAL WAVE OF PRECIP AND THIS LEFTOVER  
REGION...BOUNDARY LAYER CONDITIONS HAVE BEEN MUCH CLOSER TO 
SATURATION AND THE WEAK OVERALL LIFT BETWEEN THESE AREAS HAS ALLOWED 
MORE BANDS OF LIGHT RAIN TO KEEP DEVELOPING FROM THE SHENANDOAH VLY 
TO THE BAY. 

PART OF THE OVERALL FORCING HAS BEEN THE PASSAGE OF AN EMBEDDED COLD 
FRONT THAT IS CURRENTLY MOVING SOUTHEAST OF MD I-95. EXPECTING TO 
SEE A CONTINUED INCREASE IN SHOWER ACTIVITY OVER THE AFOREMENTIONED 
AREAS E OF THE BLUE RIDGE THRU EARLY EVENING. AFTERWHICH...THE 
GRADUAL DECREASE IS EXPECTED...W/ THE NRN SHENANDOAH VLY CLEARING 
OUT FIRST...THEN EVENTUALLY DOWN TOWARD THE SE. SOME RESIDUAL 
SHOWERS AND A FEW MIXED-IN SNOW FLAKES POSSIBLE ACROSS THE HIGHEST 
ELEVATIONS AND SHELTERED VLYS OF THE CNTRL APLCNS. THE DECENT 
FORWARD SPEED OF THE DEVELOPING PRECIP LATE THIS AFTERNOON WILL 
STILL ONLY BE LIGHT IN TERMS OF QPF.

&&

.SHORT TERM /TUESDAY/...
OVERNIGHT LOWS WILL DROP BACK INTO SIMILAR CONDITIONS FROM TWO 
NIGHTS AGO /NEAR FREEZING/. THE COLDEST TEMPS WON/T SETTLE IN 
UNTIL THE PRE-DAWN HRS THO...SINCE THE CLOUDS-PRECIP WILL TAKE A 
BIT LONGER TO EXIT THE REGION.

DRYING WILL BEGIN AREAWIDE OVERNIGHT...W/ THE UPPER TROF AXIS 
FINALLY MAKING IT/S TREK E OF CNTRL APLCNS AND ACROSS THE REST OF 
THE MID ATLC BY THE PRE-DAWN HRS. A WEAK EMBEDDED UPPER SHORTWAVE 
WILL THEN SLIDE BY JUST TO THE NORTH...W/ LITTLE MORE THAN BREEZY 
CONDITIONS DURING THE AFTN HRS. THE LIGHT PRECIP WILL STAY WELL TO 
NORTH OF THE AREA. 

AS THIS WAVE PASSES BY...MUCH OF THE CLOUD COVER WILL ALSO REMAIN 
NORTH OF THE AREA...W/ THE SRN ZONES CLEARING OUT AND THE NRN HALF 
OF THE REGION W/ A FEW PASSING MID-LOW STRATUS. WLY WINDS WILL KEEP 
TEMPS MODERATED TUE...ONLY CLIMBING INTO THE L50S FOR MUCH OF THE 
AREA.

&&

.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
HIGH PRESSURE MOVES OFF THE EASTERN SEABOARD TUESDAY NIGHT AS LOW 
PRESSURE NEAR THE GULF COAST STRENGTHENS. RETURN FLOW WILL INCREASE 
MOISTURE...AND CWA IS LIKELY TO HAVE A DECK OF HIGH/MID CLOUDS TO 
START WEDNESDAY MORNING WELL IN ADVANCE OF LOW PRESSURE. CLOUDS WILL 
LOWER THROUGHOUT THE DAY WEDNESDAY...AND RAIN WILL LIKELY START 
ACROSS THE HIGHLANDS/SHENANDOAH VALLEY AREA DURING THE AFTERNOON 
HOURS. RAIN WILL EXPAND NORTH THROUGH THE REST OF THE CWA DURING THE 
EVENING. CATEGORICAL POPS ARE IN PLACE. 

THERE REMAINS SOME DISAGREEMENT REGARDING THE EXACT TRACK OF THE 
CYCLONE. GENERAL TREND IS FOR A MORE WESTERN TRACK. INITIAL SURGE OF 
ISENTROPIC LIFT WILL PRODUCE RAIN...BUT CWA MAY ALSO BECOME WARM 
SECTORED...WHERE ISOLATED THUNDERSTORMS MAY ALSO BE POSSIBLE 
WEDNESDAY NIGHT INTO THURSDAY MORNING BEFORE A DRY SLOT WOULD CUT 
OFF RAIN ACROSS THE CWA. NAM AND GFS INDICATE QUITE A BIT OF 
SHEAR...AND NAM ALSO SHOWS A LITTLE CAPE...SO ITS HARD TO RULE OUT 
THUNDER ESPECIALLY EAST OF THE MTNS. 12Z NAM IS ALSO SLOWER THAN THE 
12Z GFS AND ITS TIMING WAS PREFERRED. 

EXPECT COLDER TEMPERATURES TO MOVE IN THURSDAY NIGHT AND FRIDAY 
ACROSS THE CWA. EAST THE MTNS WILL CLEAR OUT SOME...ALTHOUGH CLOUDS 
AND SOME SNOW SHOWERS CAN BE EXPECTED ACROSS FAVORED SLOPES OF THE 
HIGHLANDS. 

12Z GFS HAS TRENDED MORE PESSIMISTIC FOR FRIDAY NIGHT AND 
SATURDAY...WITH A STRONGER WAVE BECOMING NEGATIVELY TILTED AS IT 
MOVES INTO THE MID ATLANTIC REGION AS SURFACE LOW PRESSURE MOVES UP 
THE EASTERN SEABOARD. 12Z CANADIAN INDICATED A SIMILAR TREND. 12Z 
ECMWF ALSO SEEMS TO TREND THAT WAY. HOWEVER...MANY OF THE 21Z GEFS 
ENSEMBLES MEMBERS ARE NOT AS ROBUST. HAVE DECENT CONFIDENCE IN A 
COLDER THAN NORMAL PATTERN IN PLACE...BUT LOW CONFIDENCE IN CHANCES 
OF PRECIP. GIVEN THE UNCERTAINTY OF THE LATTER...NO LARGE CHANGES 
WILL BE MADE AND HAVE STUCK CLOSE TO HPC. HOWEVER...IF THE 
OPERATIONAL 12Z GFS/CANADIAN HOLD...THEN SOME RAIN/SNOW COULD BE 
POSSIBLE ACROSS THE MID ATLANTIC IN THE FRIDAY NIGHT/SATURDAY TIME 
FRAME. STAY TUNED...

OTHERWISE...HIGH PRESSURE RETURNS OVER THE WEEKEND WITH A COLDER 
THAN NORMAL PATTERN CONTINUING. UNSETTLED CONDITIONS COULD COME 
BACK EARLY NEXT WEEK.

&&

.AVIATION /20Z MONDAY THROUGH SATURDAY/...
WITH A COLD FRONT NOW PUSHING SE OF I-95...MORE AREAS OF RAIN HAVE 
FILLED-IN BEHIND...KEEPING THE AREA MOIST OVER THE NEXT SEVERAL HRS. 
THE COMPLETE EXIT OF PRECIP WILL LIKELY BE LATER THIS EVENING INTO 
THE LATE NIGHT HRS...W/ A LINGERING ARM OF STEADY RAIN REACHING BACK 
INTO WV AT THIS HR. THE LOWEST LEVELS NOT INCREDIBLY MOIST...SO 
CIGS/VSBYS STILL ABLE TO REMAIN IN THE LOWEST VFR CATS /ONLY 
DROPPING IN THE HIGH-END MVFR FOR A BRIEF PERIOD UNDER HEAVIER RA 
ACTIVITY/. BRIEF GUSTY WINDS SHOULD ALSO BE TAKEN INTO ACCOUNT...W/ 
A WEAK 20-30KT JET A COUPLE THO FT UP.

OVERNIGHT...CONDITIONS WILL IMPROVE AS THIS ACTIVITY MOVES OFF THE 
MID ATLC COAST AND HIGH PRESSURE BRIEFLY BUILDS IN ON TUE. A WEAK 
UPPER WAVE WILL PASS WELL TO THE NORTH OF THE REGION TUE AFTN...THO 
THIS WILL ONLY BRING A PERIOD OF BREEZY SFC WINDS TO THE AREA TUE 
AFTN AND NO PRECIP.

HIGH PRESSURE MOVES AWAY TUESDAY NIGHT INTO EARLY 
WEDNESDAY...ALLOWING LOW PRESSURE TO APPROACH THE MID ATLANTIC. LOW 
PRESSURE WILL PRODUCE RAIN WEDNESDAY NIGHT INTO THURSDAY...WITH IFR 
CONDITIONS LIKELY. HIGH PRESSURE RETURNS FRIDAY. 

&&

.MARINE...
A COLD FRONT WILL CONTINUE DOWN THE LENGTH OF THE BAY/TP THRU THE 
REST OF THE AFTN AND INTO EARLY THIS EVENING. STEADY RAIN SHOWERS 
WILL CONTINUE THRU THIS PERIOD AS WELL...INTO LATER TONIGHT ALSO. 
OVERNIGHT...THE RAIN WILL MOVE OFF THE ATLC COAST...THO GUSTY WINDS 
WILL MOVE-IN BEHIND...MAINLY ACROSS THE MIDDLE PORTIONS OF THE BAY. 
SCA UP FOR THE WATERS EXCEPT THE 2 WRN ZONES OF THE TP...AS SCA 
WINDS OVERALL EXPECTED TO BE MARGINAL...AND THESE LOCALES DO NOT 
APPEAR THEY WILL REACH CRITERIA OTHER THAN A BRIEF INTERMITTENT GUST 
THRU THE OVERNIGHT HRS AND INTO TUE AFTN.

HIGH PRESSURE MOVES OFF THE EASTERN SEABOARD TUESDAY NIGHT INTO 
EARLY WEDNESDAY. LOW PRESSURE LIFT NORTH THROUGH THE MID ATLANTIC 
WEDNESDAY NIGHT INTO THURSDAY. GUSTY WINDS AT LEAST TO SMALL CRAFT 
ADVISORY LEVELS /AND POSSIBLY GALE FOR A PERIOD/ ARE EXPECTED AS LOW 
PRESSURE PASSES BY WEDNESDAY INTO THURSDAY.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 4 PM EST TUESDAY FOR ANZ530>533-
     538>542.
     SMALL CRAFT ADVISORY UNTIL 4 PM EST TUESDAY FOR ANZ534-537-543.

&&

$$
SYNOPSIS...GMS/PELOQUIN
NEAR TERM...GMS
SHORT TERM...GMS
LONG TERM...PELOQUIN
AVIATION...GMS/PELOQUIN
MARINE...GMS/PELOQUIN