550 
FXUS61 KLWX 211943
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
243 PM EST SAT NOV 21 2009

.SYNOPSIS...
HIGH PRESSURE WILL REMAIN OVER THE REGION TONIGHT BEFORE SETTLING 
OVER NEW ENGLAND SUNDAY. AN AREA OF LOW PRESSURE WILL DEVELOP OFF 
THE MID-ATLANTIC COAST MONDAY BEFORE SLOWLY MOVING UP THE 
EASTERN SEABOARD MONDAY NIGHT INTO TUESDAY...BRINGING RAIN. HIGH
PRESSURE WILL BRIEFLY BUILD IN LATE TUESDAY INTO WEDNESDAY...BUT
ANOTHER COLD FRONT WILL PASS THROUGH LATE IN THE WEEK. 
&&

.NEAR TERM /THROUGH TONIGHT/...
CURRENT ANALYSIS SHOWS AN AREA OF HIGH PRESSURE OVER THE OHIO VALLEY 
THAT EXTENDS INTO THE MID-ATLANTIC. A SPLIT JET CONTINUES ACROSS THE 
CENTRAL AND EASTERN CONUS. AN UPPER-LEVEL LOW IN THE NORTHERN BRANCH 
IS MOVING INTO PENNSYLVANIA THIS AFTERNOON WHILE AN UPPER-LEVEL LOW 
IN THE SOUTHERN BRANCH TRACKS INTO THE GULF COAST STATES. 

SURFACE HIGH PRESSURE WILL CONTINUE TO BRING DRY AND SEASONABLE 
CONDITIONS TONIGHT. THE STRATO CU DECK ASSOCIATED WITH THE 
UPPER-LEVEL LOW OVER PA SHOULD DISSIPATE ACROSS MOST AREAS THIS 
EVENING WITH THE LOSS OF DAYTIME HEATING. HOWEVER...CLOUDS MAY HANG 
ON ACROSS THE NORTHWESTERN CWA INTO THE POTOMAC HIGHLANDS WHERE 
THERE IS A LITTLE MORE LOW-LEVEL MOISTURE. MIN TEMPS WILL RANGE FROM 
THE LOWER AND MID 30S IN PORTIONS OF THE POTOMAC HIGHLANDS INTO THE 
SHENANDOAH VALLEY...TO THE MID 40S IN DOWNTOWN WASHINGTON/BALTIMORE. 
&&

.SHORT TERM /SUNDAY/...
THE UPPER-LEVEL LOW CURRENTLY LOCATED OVER PENNSYLVANIA WILL SLOWLY 
TRACK SOUTH INTO OUR REGION WHILE THE SURFACE HIGH BUILDS TOWARD NEW 
ENGLAND SUNDAY. THE SOUTHERN BRANCH SYSTEM WILL TRACK INTO THE 
SOUTHEASTERN CONUS...BUT IT SHOULD REMAIN FAR ENOUGH TO OUR SOUTH 
NOT TO HAVE ANY IMPACT ON OUR WEATHER THROUGH SUNDAY. 

A LOW-LEVEL NORTH-NORTHEAST FLOW AROUND HIGH PRESSURE TO OUR NORTH 
WILL KEEP DRY CONDITIONS IN PLACE ALONG WITH SUNSHINE. MAX TEMPS 
WILL TOP OFF IN THE MID TO UPPER 50S ACROSS MOST LOCATIONS...BUT 
UPPER 40S IN THE HIGHER ELEVATIONS.  
&&

.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
GDNC TRENDING MUCH SLOER...HOLDING OFF PCPN SUN NGT AS STRONG HIPRES 
OVR NEW ENGLND RDGS DWN ATLC CST. EMPHASIS OF RAFL NOW MON-MON 
NGT...AS A WK WV IN THE SRN STREAM SPILLS MSTR NWD...AND EVENTUALLY 
SPAWNS CSTL LOW. WAA ON SRN DOORSTEP SUNSET SUN...AND CLDS WL 
THICKEN/LWR THRU EVE. WL BRING POPS INTO GRIDS LT SUN EVE/SUN 
OVNGT...SPCLY SRN CNTYS WHICH IS NEARER TRIGGERING MECHANISM.

BY MON-MON NGT...ENERGY WL TRANSFER OFF CST. PCPN WL BE IN RESPONSE 
TO DVLPG LOW...MOSTLY IN DEFORMATION ZN. HV LINGERED A CHC INTO 
TUE...SPCLY NRN CNTYS. HWVR...CAA SHUD BE ABLE TO MIX OUT THE DEEP 
MSTR. BUT...FLOW WONT GO WLY...AND AS SUCH AM AFRAID WL HOLD ONTO A 
PRTL MARINE DECK INTO MIDWK. PER XTNDD DSCN 2 PARAGRAPHS DWN...FCST 
AT THIS PT BECOMES A BIT MORE UNCERTAIN...AND GRIDDED DETAILS BECOME 
BROADER IN SCOPE.

PER TEMPS...HV LMTD DIURNAL SWINGS IN RESPONSE TO CLDCVR NXT CPL 
DAYS...GOING ON HIGH SIDE FOR MIN-T...AND LOW END FOR MAXT. DID 
SHADE DWNWD MON NGT SINCE CWFA WL BE AFFECTED BY CAA BY THEN.

WE/VE ENTERED THE TIME OF YEAR WHEN SPLIT FLOW WRECKS HAVOC ON MDL 
SOLNS. IT APPEARS WE/RE ENTERING SUCH A PD. THE MAIN FCST CHALLENGES 
REVOLVE ARND S/WV ENERGY DIGGING INTO TROF ACRS THE PLAINS...LKLY 
CUTTING OFF AN UPR LOW...AND THEN TRAVERSING THE CONUS AS ADDTL 
PIECES OF S/WV ENERGY DIVE INTO THE TROF AXIS. GFS AND GGEM DEEPER 
AND QUICKER W/ H5 LOW...WHICH IS ALMOST CONTRADICTORY. WL TAKE A 
HIGHLY ENSEMBLED APPROACH...LEANING ON STEADIER ECMWF. REGARDLESS... 
WL HV AN UPR TROF IN THE NEIGHBORHOOD /PRBLY CNTRD OVR THE GRTLKS/ 
THIS THXGVG...WHICH MEANS THE XTNDD FCST WL START OUT WARM...THEN HV 
A CFP COOL CWFA OFF. THERE ALSO WL BE THE SUPPORT FOR PCPN-- RA AT 
1ST...BUT HGTS/TKNSS/H8 TEMPS WUD SUPPORT AT LEAST SOME SNW...SPCLY 
FOR THE MTNS BY THU NGT..WHICH MAY CONT INTO FRI ACRS WRN UPSLP 
AREAS. POP FCST LOW CONFIDENCE ATTM...BUT WL CONT TO BE MONITORED 
DUE TO POTL TRVL IMPACTS. THE WRN UPSLP ASPECT TO THE FCST THE MOST 
SOLID.
&&

.AVIATION /20Z SATURDAY THROUGH THURSDAY/...
PATCHY BR MAY BRING A BRIEF PERIOD OF MVFR VSBYS EARLY SUNDAY 
MORNING...OTHERWISE VFR CONDITIONS ARE EXPECTED TONIGHT THROUGH 
SUNDAY. LIGHT NORTHERLY WINDS ARE EXPECTED TONIGHT...WINDS SHOULD  
REMAIN BELOW 10 KNOTS SUNDAY WITH THE DIRECTIONS VEERING TOWARD THE  
NORTHEAST. 

VFR SUN EVE...AS CLDS THICKEN/LWR FM S-N. FLGT RESTRICTIONS PSBL 
OVNGT AS RA SPREADS IN. RESTRICTIONS PREVALENT MON-MON NGT AS LOPRES 
PASSES E OF TERMINALS. 

SHUD BE A BREAK TUE-WED...THO MARINE LYR CUD POTENTIALLY HOLD ON. 
THEN...ANTHR STORM SYSTEM MVS IN WED NGT-THU...FLLWD BY COLD AIR BY 
END OF WK.
&&

.MARINE...
HIGH PRESSURE OVER THE WATERS TONIGHT WILL BUILD TOWARD THE NORTH 
SUNDAY. NORTHERLY WINDS TONIGHT WILL VEER TOWARD THE NORTHEAST 
DURING THE DAY SUNDAY. WIND SPEEDS WILL REMAIN BELOW SCA CRITERIA. 

WK WV OF LOPRES TRACKS ACRS SERN CONUS SUN NGT...AND 
TRANSFERS/DEEPENS OFF DELMARVA MON-MON NGT. WNDS INCR DURING THIS 
PD...W/ SCA CONDS PSBL.

IN WAKE OF THIS LOW AND IN ADVC OF NXT STORM SYSTM...N WNDS VEER 
ELY. MORE PCPN WL SPREAD IN MIDWK...BUT SCA NOT XPCTD ATTM.
&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...BJL
NEAR TERM...BJL
SHORT TERM...BJL
LONG TERM...HTS
AVIATION...BJL/HTS
MARINE...BJL/HTS