000 FXUS61 KLWX 220015 AAA AFDLWX AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 715 PM EST SAT NOV 21 2009 .SYNOPSIS... HIGH PRESSURE WILL REMAIN OVER THE REGION TONIGHT BEFORE SETTLING OVER NEW ENGLAND SUNDAY. LOW PRESSURE WILL DEVELOP OFF THE MID- ATLANTIC COAST MONDAY BEFORE MOVING SLOWLY UP THE EAST COAST MONDAY NIGHT INTO TUESDAY...BRINGING RAIN. HIGH PRESSURE WILL BUILD BRIEFLY LATE TUESDAY INTO WEDNESDAY...BUT A COLD FRONT WILL PASS THROUGH LATE IN THE WEEK. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... BKN-OVC CLD CVRG RMNS SLOW TO ERODE OVER CNTRL PORTIONS OF FCST AREA. HAVE RESTRUCTURED CLD GRIDS TNGT AND INTRODUCED FOG INTO WX GRIDS. OTHERWISE...FCST GENLY IN GOOD SHAPE. TEXT PRODUCTS HAVE BEEN UPDATED. PREV DISCUSSION FOLLOWS... 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 /6 AM SUNDAY MORNING THROUGH 6 PM 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 /00Z SUNDAY THROUGH THURSDAY/... LIGHT VRB-NLY WINDS XPCD TNGT. CIGS AROUND 5 KFT MAKING SLOW WWD PROGRESS. THESE CLDS XPCD TO LINGER THRU THIS EVE AT KMRB/KIAD BUT WILL ERODE LATE THIS EVE. CLDS MAY BE REPLACED BY PATCHY MVFR FOG AS RGN WILL BE FOUND IN SWRN QUADRANT OF BROAD SFC HIPRES CNTRD IN NEW ENGLAND. INCRG CLDS SUN AFTN AS ENELY FETCH BGNS TO TRANSPORT ATLC MSTR WWD. 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... SFC HIPRES BUILDS ACRS NEW ENGLAND TNGT. NO HAZARDS XPCD THRU SUN AS WINDS VEER SLGTLY FROM NLY TO NELY. SUSTAINED WINDS AOA 10 KT XPCD SUN AMID MOSTLY SUNNY SKIES. 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. && $$ UPDATE...KRAMAR PREV DISCUSSION...LASORSA/HTS