FXUS61 KLWX 060902
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
402 AM EST SUN DEC 6 2009

.SYNOPSIS...
HIGH PRESSURE FROM THE OHIO VALLEY MOVES INTO THE MID ATLANTIC
THROUGH MONDAY AFTERNOON. A DRY BACK DOOR COLD FRONT MOVES ACROSS
THE REGION MONDAY NIGHT...BEFORE HIGH PRESSURE RETURNS ON
TUESDAY. THIS HIGH PRESSURE SYSTEM THEN MOVES OVER NEW
ENGLAND...SETTING UP A COLD AIR DAMMING SITUATION TUE NIGHT AS
PRECIPITATION APPROACHES FROM A MIDWEST STORM SYSTEM HEADS TOWARDS
THE ST. LAWRENCE VALLEY. COLD HIGH PRESSURE BUILDS THURSDAY INTO
FRIDAY. &&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
SFC HIPRES CNTRD BTWN CVG AND HTS ATTM. ITS IMPACT BEING FELT ACRS 
CWFA HWVR...AS SKIES HV CLRD ACRS MUCH OF AREA. THE ONLY XCPTN HAS 
BEEN THE APPLCHNS...BUT EVEN THERE CLDS HV BEEN SCATTERING OUT AS 
INVSN HGTS SINK.

HIPRES WL AFFECT CWFA DURING THE DAYLIGHT HRS UNDER H5 ZNL FLOW. THE 
MELTING BLANKET OF SNW MAY BE ENUF PERMIT A FEW DIURNALLY DRIVEN 
STCU TO FORM...BUT DEWPT DEPRESSIONS/DVM SUFFICIENT TO KEEP THAT 
THREAT LMTD. 

THE BIGGER DEAL WL BE TEMPS. HV KEPT MAXT ON THE LOW END OF 
GDNC...AS THERE/S NO BIG WAA SURGE AND ANY ENERGY WL INITIALLY BE 
DIVERTED TO THE MELTING SNWPACK.
&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/...
XPCT TEMPS TO TUMBLE THIS EVNG UNDER MOCLR SKIES...NIL WND...AND 
DEWPTS IN THE TEENS. HWVR...AN APPCHG UPR JET WL SUPPORT A CI SHIELD 
OVNGT...WHICH WL INHIBIT THE PLUNGE. NONETHELESS...MIN-T FCST NEAR 
THOSE DEWPTS... AND A CPL DEG UNDER MOS MEAN AWAY FM THE URBAN 
DOWNTWNS AND THE RELATIVELY WARMER BAY.
&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
TWO THINGS IN THE EXTENDED WORTH NOTING. FIRST IS THE POTENTIAL
FOR A COLD AIR DAMMING FREEZING PRECIP EVENT OF FZRA AND IP ON TUE
NIGHT INTO EARLY WED MORNING. 850-700MB THICKNESS VALUES FROM THE
GFS ARE TOO WARM TO SUPPORT SNOW...AND 1000-850MB THICKNESS AND
925MB TEMP OFF THE GFS SHOWS TRAPPED COLD AIR. AREAS SOUTH AND
EAST OF BALT/WASH METRO AREAS WILL LIKELY BE ALL RAIN.

OTHER ITEM IS THE COLD AIR BEHIND THIS FRONTAL SYSTEM...WHICH WILL
DROP THU NIGHT TEMPS DOWN INTO THE LOWER TEENS IN THE MOUNTAINS TO
EVEN THE LOWER 20S IN THE METRO AREAS. ANOTHER CHANCE FOR SOME
LIGHT WINTERY PCPN AS THE WEEKEND NEARS.

&&

.AVIATION /09Z SUNDAY THROUGH THURSDAY/...
VFR CONDS WL PREVAIL THRU VALID PD. NW WNDS AOB 10 KT THIS MRNG WL 
BECOME L/V TNGT.

LONG RANGE...FZRA AND IP LIKELY FOR MUCH OF THE REGION ON TUE
NIGHT INTO EARLY WED MRNG.
&&

.MARINE...
LRG AREA OF HIPRES OVR THE MIDWEST STARTING TO IMPACT WATERS. GUSTY 
WNDS AT DC AND NRNMST BAY HV SUBSIDED ENUF TO DROP SCA. ATTM... 
SUSTAINED 15-20 KT WNDS ELSW PRECLUDE DROPPING HEADLINES FURTHER. 
BUFKIT SNDGS SUGGEST MOMENTUM TRANSFER WL DETERIORATE TWD 12Z IN 
RESPONSE TO BLDG HIGH. WRF-ARW4 HOLDS ONTO WNDS A LTL LONGER. WRF 
GDNC ATTM CAN BE A BIT HIGH... AND HV SIDED W/ THE MORE CONSERVATIVE 
MDL SNDGS. WL STRETCH SCA TIL 12Z...AND MONITOR TRENDS.

EVENTUALLY...HIPRES WL RULE...W/ LGT WINDS /AOB 10 KT/ THRU TNGT.
&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 7 AM EST THIS MORNING FOR 
     ANZ531>534-537>543.

&&

$$
SYNOPSIS...JEL
NEAR TERM...HTS
SHORT TERM...HTS
LONG TERM...JEL
AVIATION...HTS 
MARINE...HTS