000 FXUS61 KLWX 280142 AAA AFDLWX AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 942 PM EDT WED MAY 27 2009 .SYNOPSIS... A WARM FRONT SLOWLY LIFT NORTH ACROSS THE REGION OVERNIGHT AND A COASTAL LOW PRESSURE SYSTEM WILL MOVE JUST OFF THE MID ATLANTIC COAST INTO EARLY THURSDAY. A COLD FRONT WILL MOVE THROUGH THE AREA FROM THURSDAY NIGHT INTO FRIDAY...WITH UNSETTLED CONDITIONS POSSIBLE UNTIL THEN. A SECONDARY COLD FRONT APPROACHES SATURDAY AND CROSSES THE AREA IN THE MIDDLE PART OF THE WEEKEND. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... MARINE HAS BUT ERODED FROM THE SLOWLY MOVING WARM FRONT THAT HAS TREKKED BACK NWD ACROSS THE MID ATLC. THERE ARE LINGERING EFFECTS OF THE MARINE LAYER UP ACROSS THE LEE SIDE OF THE MD BLUE RIDGE TO JUST W OF THE BALT METRO AREA. THE REST OF THE AREA...ESPC ACROSS THE REST OF THE MID ATLC PIEDMONT REGION HAS CLEARED OUT. WINDS HAVE DIED DOWN TO NEARLY CALM CONDITIONS AND THE NEAR SATURATED SFC CONDITIONS ARE AIDING IN THE DEVELOPMENT OF SCATTERED AREAS OF FOG. A BROKEN AREA OF 5-7KFT DECKS INCOMING FROM THE SW...WHICH SHOULD HELP TO KEEP WIDESPREAD DENSE FOG FROM DEVELOPING...AT LEAST IN THE NEXT FEW HOWEVER...A CASE CAN BE MADE FOR AREAS ADJACENT TO THE WRN SIDE OF BAY FOR AT LEAST SMALL SCALE AREAS OF DENSE FOG. MUCH OF THE RAINFALL COMING INTO THE CENTRAL APLCNS FROM THE WINDWARD SIDE OF THE MTNS ARE MEETING A STEADY DEMISE...W/ LITTLE OF IT MAKING THE TREK INTO THE CNTRL SHENANDOAH VLY. THE ONE EXCEPTION HAS BEEN THE POTOMAC HILANDS...WHICH HAVE RECEIVED A DECENT AMOUNT OF RAINFALL OVER THE PAST SEVERAL HRS /NEARLY AN INCH OVER THE NWRN 3 ZONES AND ISOLATED AREAS NEAR 2 INCHES/. THIS IS GOOD FOR AN AREA THAT ALL BUT MISSED OUT ON THE ACTIVITY A COUPLE OF DAYS AGO. THE COASTAL LOW...NOW JUST OFF THE VA TIDEWATER REGION HAS CONTINUED TO REINFORCE COOLER ENELY FLOW. BUT W/ THIS FLOW DEPLETED AND SUN ALREADY SET...CONDITIONS ARE RIPE FOR ANOTHER PSEUDO MARINE LAYER TO DEVELOP...NOT SO MUCH W/ ELY FLOW REINFORCING LOW STRATUS DECK BUT A NEAR SFC INVERSION SETTING UP W/ WHAT LITTLE HEATING TOOK PLACE THIS AFTN. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/... WL BE OFF TO A FOGGY/DREARY START TMRW...BUT AS CSTL SFC LOW KICKS NWD...THE SLY H8 FLOW SHUD FINALLY BE ABLE TO ERODE THE MARINE LYR. APPCHG CDFNT FM MIDWEST WL ALSO ASSIST IN SHARPENING FLOW AND ERODING MARITIME AMS. GIVEN THE HUMID NATURE OF THE AIR TO OUR S/W...THAT WL LEAD TO TSRA DVLPMNT. HWVR...NAM STBLTY FIELDS STILL REFLECT IMPACT OF THE STBL WEDGE NEAR BAY...SO AM RELUCTANT TO BRING TSRA INTO BALT. THE BETTER SUPPORT WL BE INVOF CDFNT...SO HIER POPS /CAT/ WL BE W OF I-95...AND WL BE TAPERING OFF TO CHC SE. MOS MAXT SIMLR TO PRVS FCST...AND MATCHES OBS IN UPR OHVLY ATTM. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... ACTIVE PATTERN PERSISTS INTO FRIDAY. WHILE THE FOCUS OF STORM ACTIVITY THURSDAY SHOULD BE LATE AFTERNOON/EVENING...PWAT VALUES IN THE 1.8IN RANGE AND CONTINUED SURFACE BASED INSTABILITY /AT LEAST FROM DC AND SOUTH/WEST WITH POSSIBLE STABLE MARINE LAYER STILL EAST AND NORTH OF DC/ KEEP WIDESPREAD SHOWERS WITH THUNDER THROUGH THE MIDNIGHT TIMEFRAME. SHOWERS WITH LESS LIKELIHOOD OF THUNDER PERSIST THROUGH THE NIGHT AS A SLOWING COLD FRONT ENTERS THE AREA FROM THE WEST. UPR TROF DESCENDS ACROSS THE ERN CONUS SATURDAY. GFS/EURO IN AGREEMENT THAT THE AMPLIFICATION OF THE TROF IS GREAT ENUF TO BRING A COUPLE WEAK REINFORCING COLD FRONTS ACROSS THE MID ATLANTIC AREA OVER THE WEEKEND. GIVEN W/NW FLOW WITH THE FRONT WENT WITH CHC POPS FOR UPSLOPE PROCESSES ACROSS WESTERN RIDGES SATURDAY...SATURDAY NIGHT...AND INTO SUNDAY WITH SCHC FOR TSTMS EAST OF THE RIDGES TO THE BAY SATURDAY AFTERNOON/EARLY EVENING. SEMI ACTIVE PATTERN LOOKS TO CONTINUE WITH ANOTHER COLD FRONT CROSSING THE AREA EARLY NEXT WEEK. && .AVIATION /01Z THURSDAY THROUGH MONDAY/... THE MARINE LAYER HAS BROKEN UP INTO A RANDOM ASSORTMENT OF SCT-BKN 2-3KFT CIGS BUT MUCH OF THE REGION HAS PRETTY MUCH CLEARED OUT. AREAS THAT STILL STAY MOSTLY CLOUDY INTO THE OVERNIGHT HRS ARE THE SHENANDOAH VLY AND CLOSER TO THE MD/PA BORDER. SOME OF THESE MID- LOW CLOUDS WILL STREAM INTO THE PIEDMONT REGIONS...BUT NOT BEFORE AREAS OF FOG BEGIN TO DEVELOP AND SPREAD ACROSS THE I-95 CORRIDOR. TAF SITES ACROSS THE MID ATLC ARE EXPECTED TO EXPERIENCE AT LEAST A FEW HRS OF IFR OR LOWER VSBYS...POSSIBLY CIG HEIGHTS FROM THIS FOG AS WELL...BUT CLOSER TO THE PRE-DAWN HRS. THIS ACTIVITY EXPECTED TO HANG ON A BIT...EVEN AFT SUNRISE. TYPICALLY W/ CALM CONDITIONS AND SCTD CLOUD DECKS...IT TAKES A COUPLE MORE HRS TO CLEAR OUT SFC CONDITIONS TILL 15-16Z. AFTER A DREARY START...CONDS WL SLOWLY IMPV DURING THE MRNG HRS. THE MORNING PUSH WL BE IMPACTED BY IFR OR LWR. VFR MAY BRIEFLY RTN BY 16Z...BUT MAY BE LATER...PENDING PROGRESS OF WMFNT. THEN...SCT-NMRS SHRA/TSRA WL DVLP IN WARM SECTOR IN ADVC OF CDFNT. PARTICULARLY UNSETTLED PATTERN CONTINUES INTO FRIDAY AHEAD OF A COLD FRONT THAT CROSSES THE AREA ON FRIDAY. SHOWERS AND THUNDERSTORMS CONTINUE INTO THURSDAY NIGHT. A COUPLE OF WEAK COLD FRONTS CROSS THE AREA OVER THE WEEKEND WITH FEW SUBVFR CONDS EXPECTED...PERHAPS ON SATURDAY AFTERNOON. ANOTHER FRONT LOOKS TO AFFECT THE AREA EARLY NEXT WEEK. && .MARINE... NO MARINE HAZARDS XPCTD. WNDS NEAR CALM OR JUST INTO THE 5KT RANGE. XPCTG FOG TO DVLP IN MARINE AMS OVNGT. WMFNT TO PUSH N TMRW /IT HAS BETTER SUPPORT THAN IT DID TDA/...ALLWG FLOW TO VEER SLY BY AFTN. THEN... SCT-NMRS SHRA/TSRA WL DVLP IN WARM SECTOR IN ADVC OF CDFNT. SELY WINDS AROUND 15 KT CONTINUE TOMORROW EVENING IN ADVANCE OF A COLD FRONT APPROACHING FROM THE WEST. PRECIPITATION CHANCES /THUNDER GIVING WAY TO SHOWERS TOMORROW NIGHT/ CONTINUE UNTIL FRONT CROSSES THE WATERS ON FRIDAY. WLY/NWLY WINDS AFTER A COUPLE OF WEAK COLD FRONTS CROSSING FROM THE WEST OVER THE WEEKEND. ANOTHER FRONT LOOKS TO AFFECT THE AREA EARLY NEXT WEEK. && .TIDES/COASTAL FLOODING... NO CHG TO WATER LVLS. MOST OB SITES STILL REPORTING TIDAL ANOMALIES A HALF FOOT TO FOOT ABOVE NORMAL /BUT CLOSER TO HALF A FOOT/. WATER LEVELS ARE FORECAST TO REMAIN BELOW MINOR TIDAL FLOODING AND NO INTENSE WIND COMPONENT EXPECTED TO INCREASE THESE ANOMALIES AGAIN THRU AT LEAST THE NEXT 24 HRS...SO WILL TAKE OUT THE TIDES UP TO 1 FT WORDING IN CWF. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ UPDATE...GMS PREV DISCUSSION...HTS/BAJ