Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 210749 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 349 AM EDT SUN SEP 21 2014 .SYNOPSIS... LOW PRESSURE WILL TRACK NORTH ALONG THE SOUTHEAST AND MID ATLANTIC COASTS TODAY. A COLD FRONT WILL CROSS THE REGION LATE THIS AFTERNOON INTO THIS EVENING...FOLLOWED BY A RETURN OF HIGH PRESSURE MONDAY THROUGH WEDNESDAY. && .NEAR TERM /THROUGH TONIGHT/... DEVELOPING LOW PRESSURE WILL MOVE ALONG THE CAROLINA COAST THIS MORNING BEFORE HEADING OUT TO SEA THIS AFTERNOON. RAINBANDS ASSOCIATED WITH THIS SYSTEM ARE EXPECTED TO REMAIN TO THE SOUTH AND EAST OF THE FORECAST AREA. SOME PATCHY FOG IS STILL POSSIBLE EARLY THIS MORNING BUT WESTERLY WINDS WILL HELP MIX OUT THE BOUNDARY LAYER AFTER SUNRISE WITH REMAINING FOG BURNING OFF. BEHIND THE DEPARTING LOW...WESTERLY WINDS WILL AID IN DOWNSLOPE WARMING ACROSS THE REGION. AFTERNOON HIGH TEMPERATURES ARE EXPECTED TO REACH THE 80S IN MOST LOCATIONS...ESPECIALLY EAST OF THE BLUE RIDGE. DAYTIME HEATING COMBINED WITH AN APPROACHING COLD FRONT WILL HELP TOUCH OFF SCATTERED AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS FIRST OVER THE POTOMAC HIGHLANDS AND I-81 CORRIDOR THEN SPREADING EAST ACROSS THE METRO AREAS LATE THIS AFTERNOON AND INTO THE EVENING. SOME OF THE STORMS COULD PRODUCE DAMAGING WINDS ALTHOUGH AN ISOLATED THREAT. CONVECTIVE THREAT WILL END BY MID EVENING. A FEW SHOWERS MAY REMAIN OVER THE POTOMAC HIGHLANDS. COOLER AND DRIER AIR WILL FILTER INTO THE REGION OVERNIGHT WITH TEMPERATURES COOLING BACK TO THE 40S TO 50S WEST AND UPPER 50S TO MIDDLE 60S EAST. && .SHORT TERM /MONDAY THROUGH MONDAY NIGHT/... HIGH PRESSURE WILL BUILD INTO THE MIDDLE ATLANTIC ON MONDAY BRINGING PLENTY OF SUNSHINE AND PLEASANT TEMPERATURES. AFTERNOON HIGHS MAINLY IN THE 60S TO LOWER 70S CAN BE EXPECTED ALONG WITH LOWS IN THE UPPER 30S TO LOW 40S WEST TO THE MID 40S TO 50S EAST OF THE BLUE RIDGE. && .LONG TERM /TUESDAY THROUGH SATURDAY/... SFC HIPRES WL BE ACROSS MOST OF THE ERN CONUS THRU THE END OF THE WK. H5 RDG WL BE BLDG TOO. AT FIRST GLANCE...THAT WUD SEEM LIKE A CUT-N-DRY FCST. HWVR...THERE IS A CATCH. ECMWF GDNC SUGGESTING A CUTOFF LOW IN THE MIDST OF THE H5 RDG...OR IN OTHER WORDS...A WEAKNESS IN THE HGT PTTN. THERE/S RATHER POOR AGREEMENT ON A FEATURE SO SUBTLE SVRL DAYS OUT. HWVR...SFC FLOW WL BE NLY TUE BUT VEER ELY WED-THU...AS THE CENTER OF THE SFC HIGH WL BE ATOP NEW ENGLAND/NYS BY THEN. AT THE VERY LEAST...CANNOT RULE OUT AN INCREASE IN MSTR AND MAYBE A SPRINKLE OR TWO /OR A PATCH OF DZ?/. SO AT THIS JUNCTURE...WL KEEP TUE SUNNY...BRING CLDS INLAND WED... AND OFFER UP SOME LOW END POPS /20-30 PCT/ WED NGT-THU. CHOOSING A STRATIFORM PCP CHARACTER. AM THINKING AS THE UPR RDG BLDS TO THE W OF THE AREA...THAT MAY BE ENUF TO ALLOW SFC RDGG TO RETROGRADE. IF THAT DOES HPPN...THEN WE/LL LOSE THE ONSHORE FLOW...AND THE MARINE AMS WL LOSE ITS GRIP ON THE RGN. DONT HV THE HIEST OF CONFIDENCE IN THIS OUTLOOK...BUT DONT WANT TO CARRY A PROLONGED PD OF LOW POPS UNDER HIPRES W/O A CLEARER SIGNAL. CAN SAY THIS...HIER HGTS WL LEAD TO WARMER TEMPS. MAXT TUE-THU NOT FAR OFF FM BAY WATER TEMPS...WHICH IS ABT 5 OR 6 DEGF COOLER THAN CLIMO. WE/LL BE BACK NEAR NORMAL AGN FRI-SUN. && .AVIATION /08Z SUNDAY THROUGH THURSDAY/... PATCHY EARLY MORNING FOG WILL GIVE WAY TO VFR CONDITIONS BY MID MORNING. SCATTERED SHOWERS AND THUNDERSTORMS WILL DEVELOP THIS AFTERNOON AND EVENING AHEAD OF A COLD FRONT. SOME IMPACT TO THE TERMINALS MAY BE POSSIBLE...ESPECIALLY 18-00Z. PATCHY FOG COULD REDEVELOP LATE TONIGHT INTO EARLY MONDAY. OUTLOOK... MON-TUE...VFR UNDER HIPRES. WED-THU...ONSHORE FLOW MAY BRING A STRATUS DECK INLAND. FLGT RESTRICTIONS PSBL...BUT CONFIDENCE LOW. && .MARINE... WINDS WILL REMAIN BELOW SCA LEVELS TODAY EXCEPT WHERE SHOWERS AND THUNDERSTORMS DEVELOP LATE THIS AFTERNOON INTO THIS EVENING. SCA CONDITIONS ARE EXPECTED BEHIND A COLD FRONT OVERNIGHT THROUGH MONDAY. NLY FOW TUE WL VEER ELY FOR WED-THU. GDNC SUGGESTING ELY FLOW MAY BE STIFF...POTENTIALLY SUPPORTING SCA CONDS OVER A PORTION OF THE WATERS /MID BAY/. && .TIDES/COASTAL FLOODING... TIDAL DEPARTURES...WHICH ROSE DRAMATICALLY YDA...HAVE SINCE LESSENED AS HIGH TIDE ROLLS IN. AS A RESULT...TIDES MAXING OUT RIGHT NEAR MINOR CRITERIA AT SOLOMONS/PINEY POINT/ANNAPOLIS. THE TIDE IS IN AA COUNTY RIGHT NOW. THUS WL BE ABLE TO CANX ADVY FOR CALVERT AND SAINT MARYS. FURTHER...SINCE DEPARTURES LOWER...DO NOT BELIEVE THRESHOLDS WILL BE MET AT BALTIMORE. WILL CANCEL THAT ONE AS WELL. DO NOT HAVE A GOOD FEEL FOR THE UPPER POTOMAC RIGHT NOW...SO WILL ALLOW THOSE ADVYS TO CONTINUE. THE PM TIDE WILL BE A BIT MORE OF A CHALLENGE TO FORECAST. IT WILL BE THE LOWER ASTRONOMICAL TIDE. SWLY WINDS WILL BECOME WLY...SO PERHAPS WE WILL GET A PINCH OF RELIEF FROM THAT. AND...BASELINE DEPARTURES GOING IN APPEAR TO BE BELOW +1. ALL SAID...WL FOLLOW THE PREMISE THAT REACHING CAUTION STAGE PROBABLE BUT MINOR THRESHOLD LESS LIKELY. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...COASTAL FLOOD ADVISORY UNTIL 9 AM EDT THIS MORNING FOR DCZ001. MD...COASTAL FLOOD ADVISORY UNTIL 8 AM EDT THIS MORNING FOR MDZ014. VA...COASTAL FLOOD ADVISORY UNTIL 9 AM EDT THIS MORNING FOR VAZ054. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM 4 AM TO 6 PM EDT MONDAY FOR ANZ530>543. && $$ SYNOPSIS...HTS NEAR TERM...KRW SHORT TERM...KRW LONG TERM...HTS AVIATION...HTS/KRW MARINE...HTS/KRW TIDES/COASTAL FLOODING...HTS

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