Area Forecast Discussion
Issued by NWS Sterling, VA

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KLWX 170058 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 858 PM EDT SAT AUG 16 2014 .SYNOPSIS... A WEAK COLD FRONT WILL APPROACH THE REGION TONIGHT. THE COLD FRONT WILL THEN BECOME STATIONARY OVER THE SOUTHERN CHESAPEAKE BAY THROUGH MONDAY. LOW PRESSURE OVER THE OHIO VALLEY WILL APPROACH THE AREA LATE MONDAY...AND RIDE EAST ALONG THE STATIONARY FRONT BEFORE FINALLY MOVING EAST OF DELMARVA TUESDAY. A BOUNDARY WILL THEN REMAIN STALLED SOUTH OF THE WATERS FOR THE MIDDLE PORTION OF NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... WEAK COLD FRONT CONTINUES TO PUSH SOUTHWARD ACROSS THE GREAT LAKES REGION. THIS FRONT AND ASSOCIATED UPPER WAVE WILL CONTINUE TO APPROACH THROUGH TONIGHT AND TOMORROW MORNING. THE UPPER SUPPORT WILL OUTRUN THE SFC BOUNDARY...LEAVING IT SLOW-MOVING OR STALLED BY SUNDAY AFTERNOON. BOTH THE GLOBAL MODELS AND HI-RES MODELS HAVE BACKED OFF ON THE IDEA OF PRECIP TONIGHT...AND ARE ALSO KEEPING THE PRECIP OVER PA FURTHER NORTH OWING TO THE SLOW MOVEMENT OF THE SFC BOUNDARY. HOWEVER...PLENTY OF HIGH AND MID CLOUDS ARE STREAMING INTO THE AREA AND THIS WILL CONTINUE THROUGHOUT THE NIGHT. INCREASED SKY COVER THIS EVENING AND KEPT IT HIGH ALL NIGHT. WITH THIS INCREASE IN SKY COVER ALSO COMES A LIKELY INCREASE IN LOW TEMPS TONIGHT...NUDGED CLOSER TO THE WARMER SIDE OF THE GUIDANCE SUITE. FAST FACT...THE YEAR-TO-DATE RAINFALL TOTAL AT BWI IS 37.50 INCHES. THIS IS THE SIXTH WETTEST JAN 1 THROUGH AUG 15 ON RECORD IN BALTIMORE. MEANWHILE...MARTINSBURG...HAGERSTOWN...AND CHARLOTTESVILLE ARE ALL BELOW NORMAL FOR THE YEAR-TO-DATE. && .SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/... WIDELY VARYING GUIDANCE BETWEEN THE 12Z NAM AND THE 12Z ECMWF AND 12Z GFS...WITH THE NAM BEING THE OUTLIER FOR SUNDAY. THUS HAVE DISCOUNTED THE NAM FOR SUNDAY. BOTH THE ECMWF AND GFS HAVE A QPF FROM 12-00Z IN THE EASTERN PANHANDLE OF WV AND THE CENTRAL SHEN VALLEY. ELSEWHERE IT LOOKS DRY BUT CANT RULE OUT A SCATTERED SHOWER OR THUNDERSTORM AS INSTABILITY RETURNS. SUNDAY NIGHT WILL BE PRECIP FREE AS WE ONCE AGAIN STABILIZE WITH AN ONSHORE FLOW...BUT WILL BE OVERCAST AS SFC LOW APPROACHES FROM WEST. && .LONG TERM /MONDAY THROUGH SATURDAY/... ACTIVE WEATHER RETURNS TO THE MID-ATLANTIC FOR THE COMING WORKWEEK. A FAIRLY HIGH AMPLITUDE YET LOCALIZED H5 SHORTWAVE/VORT MAX WILL BRING A SURFACE LOW ACROSS THE OHIO VALLEY MONDAY MORNING AND INTO THE MID-ATLANTIC BY MONDAY EVENING. THERE IS SOME MODEL DISAGREEMENT IN THE TRACK OF THE LOW ACROSS THE APP MTNS AND INTO THE MID-ATLANTIC...WITH THE NAM BISECTING THE CWA WITH THE LOW WHILE THE OTHER GLOBAL MODELS TAKE IT A BIT FURTHER SOUTH. THERE IS FAIRLY GOOD AGREEMENT HOWEVER IN THE TIMING AND EFFECTS OF THE SYSTEM...WITH A PLUME OF PW AROUND 1.8 INCHES COMING THROUGH OVERNIGHT MONDAY AND INTO THE MORNING TUESDAY. PERIODS OF MODERATE TO HEAVY RAIN AND AN ISOLATED THUNDERSTORM ARE POSSIBLE WITH THE SYSTEM...THOUGH CONFIDENCE IS LOW IN THE THREAT FOR FLOODING AT THIS POINT. A WEAK SURFACE BOUNDARY WILL REMAIN STALLED NEAR THE AREA IN THE WAKE OF THE LOW TUESDAY EVENING. CLOSE TO 1000 J OF CAPE IS POSSIBLE TUESDAY...BUT MAY REQUIRE SOME BREAKS IN THE CLOUDS IN ORDER TO BE FULLY REALIZED. HAVE THUNDERSTORMS IN THE FORECAST TUESDAY EVENING GIVEN THE INSTABILITY AND AND THE LOCATION OF THE STALLED BOUNDARY NEAR OUR AREA. THE SEVERE THREAT SEEMS LOW AT THIS TIME AS INSTABILITY AND SHEAR WILL BE MODEST AND ANY STORMS THAT DO FORM SHOULD DIE OUT SHORTLY AFTER SUNSET DUE THE LOSS OF THE DIURNAL INSTABILITY ENHANCEMENT. SHOWERS AND THUNDERSTORMS WILL RETURN ONCE AGAIN DURING THE DAYTIME WEDNESDAY AS AN UPPER LEVEL SHORTWAVE WILL BRING A WAVE OF LOW PRESSURE INTO THE MID-ATLANTIC RIDING ALONG THE STALLED SURFACE BOUNDARY. CHANCE POPS WILL CONTINUE INTO THE WEEKEND AS A SERIES OF WEAKER UPPER LEVEL DISTURBANCES CONTINUE TO BRING PERIODS OF ENHANCED RAINFALL. COVERAGE AND DURATION WILL HAVE TO BE REFINED IN LATER FORECASTS...BUT THE END OF THE WORKWEEK SEEMS RATHER WET AT THIS POINT. HIGH PRESSURE SHOULD BEGIN TO BUILD BACK INTO THE AREA FROM THE NORTH NEXT WEEKEND. TEMPERATURES WILL REMAIN NEAR TO A COUPLE OF DEGREES BELOW NORMAL THROUGH THE PERIOD...OWING IN LARGE PART TO THE EXPECTED PARTLY TO MOSTLY CLOUDY SKIES. && .AVIATION /01Z SUNDAY THROUGH THURSDAY/... VFR THROUGH THE TAF PERIOD WITH LIGHT WINDS. SCTD SHRA/TSRA POSSIBLE ON SUNDAY BUT CHC NOT HIGH ENOUGH TO MENTION IN TAF AT THIS TIME. PERIODS OF IFR CONDITIONS ARE EXPECTED AS A WAVE OF LOW PRESSURE WILL BRING LOW CEILINGS TO THE AREA MONDAY EVENING THROUGH TUESDAY MORNING. PERIODS OF SHOWERS AND THUNDERSTORMS MAY ALSO EFFECT AVIATION TUESDAY EVENING AND WEDNESDAY. && .MARINE... WINDS BLO SCA THROUGH 36 HOURS...WITH CHC OF TSTMS SUNDAY AFTERNOON. A WAVE OF LOW PRESSURE WILL CROSS THE CHESAPEAKE BAY DURING THE DAY TUESDAY AND A SMALL CRAFT ADVISORY MAY BE NECESSARY TUESDAY EVENING ACROSS THE LOWER MARYLAND PORTION OF THE CHESAPEAKE BAY DUE TO THE CHANNELING OF NORTHERLY WIND. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ SYNOPSIS...LEE NEAR TERM...JE SHORT TERM...LEE LONG TERM...CEB AVIATION...JE/LEE/CEB MARINE...LEE/CEB

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.