Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 260221 AAB AFDLWX AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 1021 PM EDT MON AUG 25 2014 .SYNOPSIS... HIGH PRESSURE WILL CENTER OVER THE REGION TONIGHT AND PERSIST THROUGH WEDNESDAY BEFORE A WEAK COLD FRONT PASSES THROUGH THE AREA WEDNESDAY NIGHT. HIGH PRESSURE WILL CROSS THE NORTHERN MID-ATLANTIC THURSDAY AND LINGER OFFSHORE INTO THE WEEKEND. && .NEAR TERM /THROUGH TUESDAY/...
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UPDATE...CANCELLED COASTAL FLOOD ADZY FOR THE WASHINGTON CHANNEL AREA. MUCH OF THE ERN SEABOARD IS UNDER A LARGE AREA OF SFC HIGH PRESSURE...A FUNCTION OF THE TILTED UPPER RIDGE AXIS. THIS IS THE ERN EXTENT OF THE LARGE UPPER RIDGE THAT KEPT MUCH OF THE SRN HALF OF THE CONUS MOIST/HOT OVER THE PAST FEW DAYS AND IT IS NOW LEANING OVER THE EAST COAST. THE EFFECTS OF THIS PORTION OVERHEAD ARE MINIMAL COMPARED TO AREAS FURTHER SOUTH - SINCE WE ARE ON THE NRN EDGE OF IT WHICH IS BEING SHEARED AWAY/MIXED OUT BY THE FAST- MOVING UPPER TROUGH SLIDING JUST N OF THE GREAT LAKES REGION. MORE VALLEY FOG POSSIBLE OVERNIGHT AS TEMPERATURES DROP INTO THE U40S-L50S WEST OF THE BLUE RIDGE. AREAS E OF THE BLUE RIDGE DECOUPLED CONDITIONS WILL ALLOW TEMPERATURES TO DROP INTO THE MID TO U50S...M/U60S NEARSHORE AND URBAN AREAS. TUESDAY... CENTERED DIRECTLY OVER THE MID ATLC...THE SFC HIGH WILL PIVOT SLOWLY OVER THE AREA TONIGHT INTO TMRW KEEPING CONDITIONS ABOUT AS CALM/QUIET AS THEY CAN BE FOR LATE AUG. WINDS TMRW AT THE SFC WILL BE CIRCLING THE AREA IN A CLOCKWISE FASHION...ALBEIT ONLY A FEW KTS AT BEST - W/ NEAR CALM WIND IN THE MIDDLE. THIS FLOW WILL KEEP THE HIGHER DEWPOINTS LIMITED TO THE COASTLINE AND ALLOW FOR RELATIVELY DRIER AIR TO FUNNEL IN FROM THE NORTH. HIGHS WILL AGAIN TOP OUT IN THE L-M80S...W/ THE HIGHEST VALUES IN THE METRO DC/BALT AREAS.
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&& .SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/... WEDNESDAY...WEAK COLD FRONT APPROACHES FROM THE NORTHWEST THROUGH THE DAY. BETTER MIXING AND 18C 850MB TEMPS SHOULD ALLOW MAX TEMPS AROUND 90F. ISO/SCT THUNDERSTORMS ARE EXPECTED THAT EVENING WITH THE ACTIVITY AS INSTABILITY INCREASES WITH LI OF -3 TO -5. && .LONG TERM /THURSDAY THROUGH MONDAY/... A STALLED FRONTAL BOUNDARY SOUTH AND EAST OF THE AREA WILL BRING A CHANCE OF SHOWERS TO THE SOUTHERN PORTIONS OF THE POTOMAC HIGHLANDS AND SHENANDOAH VALLEY THURSDAY AFTERNOON AND EVENING. HIGH PRESSURE WILL BUILD INTO THE MID ATLANTIC FROM THE NORTH THURSDAY NIGHT AND REMAIN THROUGH FRIDAY...FORCING THE SURFACE BOUNDARY FURTHER SOUTH AND KEEPING THE ENTIRE CWA DRY. AS THIS HIGH PRESSURE MOVES EAST THE SURFACE BOUNDARY WILL RETURN NORTH...BRINGING A CHANCE OF RAIN TO THE AREA DURING THE DAY SATURDAY. WARM AND HUMID AIR WILL FILL IN AS THIS FRONT MOVES THROUGH THE AREA DURING THE DAY...LEADING TO INCREASED INSTABILITY AND A CHANCE OF THUNDERSTORMS SATURDAY EVENING. A SHORTWAVE TROUGH WILL LIFT A SURFACE LOW THROUGH THE GREAT LAKES REGION AND ACROSS THE NORTHEAST SUNDAY. THE ASSOCIATED COLD FRONT WILL APPROACH...AND STALL OVER OR NEAR THE AREA BY SUNDAY AFTERNOON...BRINGING THE CHANCE FOR SHOWERS AND THUNDERSTORMS TO THE MID-ATLANTIC SUNDAY AFTERNOON THROUGH MONDAY. TEMPS WILL BE NEAR TO SLIGHTLY BELOW NORMAL FRIDAY AND SATURDAY...WITH HIGHS IN THE LOWER TO MID 80S AS WE STAY ON THE COOL SIDE OF THE SURFACE BOUNDARY. HIGHS WILL INCREASE TO A COUPLE OF DEGREES ABOVE NORMAL...IN THE UPPER 80S...AS THE BOUNDARY MOVES TO OUR NORTH AND PREFRONTAL SOUTHERLY FLOW TAKES OVER SATURDAY AND SUNDAY. LOWER 80S SHOULD RETURN FOR THE BEGINNING OF THE WORKWEEK AFTER THE COLD FRONT MOVES THROUGH. && .AVIATION /02Z TUESDAY THROUGH SATURDAY/... HIGH PRESSURE/VFR INTO WEDNESDAY OUTSIDE OF MORNING FOG - MAINLY FOR KMRB/KCHO. WEAK COLD FRONT CROSSES WEDNESDAY NIGHT WITH SCT TSRA. CONFIDENCE IS LOW IN THE OCCURRENCE OF ANY HAZARDS TO AVIATION IN THE LONG TERM. && .MARINE... LIGHT ELY FLOW OVERNIGHT. ONSHORE FLOW CONTINUES THROUGH TOMORROW AS HIGH PRESSURE PERSISTS TO THE NORTH. LIGHT AND VARIABLE FLOW UNDER THE HIGH LATE TUESDAY INTO WEDNESDAY. WEAK COLD FRONT CROSSES THE WATERS WEDNESDAY NIGHT BRINGING SCATTERED THUNDERSTORMS. CONFIDENCE IS LOW IN THE OCCURRENCE OF ANY MARINE HAZARDS THROUGH THE LONG TERM. && .TIDES/COASTAL FLOODING...
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WATER LEVEL DEPARTURES HAVE SLOWLY BEEN RECEDING THIS EVENING...AND ARE BEGINNING TO SLIDE BELOW 1 FT ABOVE NORMAL. TIDES FOR THE MON PM CYCLE HAVE BEEN COMING IN UNDER THE THRESHOLD FOR MINOR FLOODING. THE PREFERRED HIGH TIDE IS TUESDAY MORNING. HOWEVER...BASED ON TRENDS THIS EVENING...CONFIDENCE IS TOO LOW IN REACHING MINOR CRITERIA TO ISSUE AN ADVISORY AT THIS TIME. THE TIDE CYCLE REACHES PT LOOKOUT AT 222 AM...AND SPREAD NORTH TO THE UPR TIDAL POTOMAC BY 930-945 AM...AND THE NORTHERN BAY BY 11 AM. WE WILL CONTINUE TO MONITOR. IF LATER INFO PAINTS A DIFFERENT PICTURE...A SHORT FUSED ADVY MAY STILL BE POSSIBLE.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE.
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&& $$ UPDATE...GMS PREV DISCUSSION...BAJ/CEB

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