Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 040821 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 421 AM EDT MON MAY 4 2015 .SYNOPSIS... HIGH PRESSURE BECOMES ANCHORED OFF THE MID ATLANTIC COAST THROUGH WEDNESDAY. A BACKDOOR COLD FRONT APPROACHES FROM THE NORTH THURSDAY. && .NEAR TERM /THROUGH TONIGHT/... HIGH PRESSURE HAS MOVED PRIMARILY OFF THE COAST AND HAS FLATTENED OUT...WITH THE MORE DOMINANT CENTRAL PRESSURE FIELDS EXPECTED ACROSS THE CAROLINAS TONIGHT. MEANWHILE...A TROUGH OF LOW PRESSURE CROSSES NEW ENGLAND LATER TODAY THROUGH TONIGHT. THE PRESSURE GRADIENT BTWN THESE TWO SYSTEMS WILL BEGIN TO TIGHTEN TODAY AS WINDS BECOME MORE S-SW. EXPECT BREEZY WINDS THIS AFTN WITH GUSTS OF 15-20 MPH. AMPLE SUNSHINE AND DECENT MIXING WILL ALLOW HIGHS TO CLIMB INTO THE LOW-MID 80S (EXCEPT NEAR OCEAN CITY WHERE HIGHS WILL ONLY REACH THE LOW-MID 70S DUE TO SLY ONSHORE WINDS ALONG THE ATLANTIC COASTLINE OF MD). A MILD NIGHT AHEAD IN CONTINUED S-SW FLOW. EXPECT LOWS IN THE UPPER 50S TO LOWER 60S. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... FLATTENED HIGH PRESSURE REMAINS ACROSS THE CAROLINAS TUESDAY AS THE NEW ENGLAND TROUGH DRAGS A RELATIVELY FLAT FRONTAL BOUNDARY ALONG THE MASON-DIXON LINE TUESDAY INTO TUESDAY NIGHT. LATEST 00Z MODEL CROSS SECTIONS ARE NOW SHOWING A SLIGHT INCREASE IN AVAILABLE MOISTURE WITH SLIGHTLY STRONGER OMEGA FIELDS DURING THE LATE AFTN/EARLY EVENING TIMEFRAME (OR DURING BEST DAYTIME HEATING/INSTABILITY). HOWEVER...2-D PRECIPITATION FIELDS ALSO INDICATE THAT AVAILABLE MOISTURE IS GETTING SHEARED APART AS IT APPROACHES THE MID ATLANTIC REGION. WILL NEED TO KEEP AN EYE ON WATER VAPOR TRENDS AS THE CURRENT COMPLEX IN THE MIDWEST SHIFTS TWD NEW ENGLAND WITH THE TROUGH/SFC FRONTAL BOUNDARY. HAVE THEREFORE HELD ONTO SLIGHT CHANCE POPS FROM LOUISA COUNTY TO THE NRN NECK TO THE MD LOWER EASTERN SHORE BEGINNING LATE TUE AFTN... INCREASING TO CHANCE POPS (NO HIGHER THAN 30%) TUE EVENING ACROSS THE NRN NECK AND MD/VA EASTERN SHORE. SW WINDS AND TEMPS WARMING INTO THE MID 80S FOR HIGHS WILL HELP TO DESTABILIZE THE ATMOSPHERE... AND THUNDERSTORMS MAY BE POSSIBLE IN THE AFTN/EARLY EVENING. MODEL CROSS SECTIONS INDICATE THAT MOISTURE FIELDS DIMINISH AFTER MIDNIGHT TUESDAY NIGHT...HOWEVER LIGHT SHOWERS MAY LINGER OVER THE MD LOWER EASTERN SHORE OVERNIGHT TUESDAY SO KEPT SLIGHT CHANCE POPS HERE DURING THIS TIME. ANOTHER NIGHT WITH MILD LOWS IN THE UPPER 50S TO LOWER 60S. FORECAST MODELS THEN DIVERGE IN THEIR SOLUTIONS BEGINNING WEDNESDAY. HIGH PRESSURE BUILDS DOWN FROM CANADA AND NORTH OF THE RELATIVELY FLAT SFC FRONT NEAR THE MASON-DIXON LINE. MEANWHILE... LOW PRESSURE DEVELOPING OFF THE EAST COAST OF FLORIDA IS EXPECTED TO LIFT TWD THE SOUTHEAST COAST INTO WEDNESDAY NIGHT. THERE IS SOME AGREEMENT AMONGST MODELS TO KEEP PRECIP OVER THE AREA THROUGH WEDNESDAY AS THE SFC BOUNDARY SAGS SWD AND A LEESIDE TROUGH STARTS TO DEVELOP. THE EXACT LOCATION AND TIMING OF PRECIP IS WHAT IS IN QUESTION AND HAVE THEREFORE TRIED TO SPLIT THE DIFFERENCE BTWN THE MORE AGGRESSIVE GFS...THE DRIER NAM...AND THE MIDDLE OF THE ROAD ECMWF. THIS SHOULD KEEP LIGHT SHOWERS OVER THE NRN HALF OF THE FA (NORTH OF RICHMOND) WEDNESDAY MORNING...WHICH SHOULD THEN SHIFT WWD DURING WEDNESDAY AFTN/EVENING AS ADDITIONAL INSTABILITY TRIGGERS SHOWERS NEAR THE LEE TROUGH BOUNDARY. THUNDERSTORMS ARE POSSIBLE ONCE AGAIN WEDNESDAY AFTN/EARLY EVENING. ANY PRECIPITATION THAT OCCURS IS EXPECTED TO TAPER OFF THROUGH THE EVENING WITH DRY CONDITIONS OVERNIGHT. SE VA AND NE NC WILL REMAIN PRECIP-FREE ON WEDNESDAY/WEDNESDAY NIGHT. HIGHS WEDNESDAY 80-84 INLAND... MID-UPPER 70S AT THE IMMEDIATE COAST AND FOR THE MD/VA EASTERN SHORE. LOWS WEDNESDAY NIGHT REMAIN MILD WITH LOWS IN THE UPPER 50S TO LOWER 60S. && .LONG TERM /THURSDAY THROUGH SUNDAY/... FOLLOWED CLOSE TO WPC AND SUPERBLEND GUIDANCE FOR THE LONG TERM. UPPER LEVEL RIDGING WILL PREVAIL OVER THE EASTERN CONUS. A BACK DOOR COLD FRONT MOVES SOUTH OVER THE MID ATLANTIC STATES WEDNESDAY NIGHT AND THEN WASHES OUT OVER SRN PORTIONS THURSDAY. A SURFACE HIGH RIDGES INTO THE AREA FROM THE EAST. LOW PRESSURE MEANDERS OFF THE CAROLINA COAST LATE IN THE WEEK. THIS LOW HAS THE POTENTIAL TO BECOME A SUBTROPICAL STORM (SEE TROPICAL WEATHER OUTLOOK). DETAILS OF THE PROGRESS OF THE LOW ARE UNCERTAIN BUT RIDGING IS EXPECTED TO KEEP THE LOW AND ITS IMPACT TO THE SOUTH OF THE CWA. DAILY CHANCES FOR SHOWERS WITH SCATTERED AFTERNOON THUNDERSTORMS ARE EXPECTED DURING THE LONG TERM WITH POPS OF 20 TO 30 PERCENT...MAINLY OVER SRN AND WRN PORTIONS OF THE CWA. LOWERED TEMPERATURES A BIT THURSDAY BEHIND THE BACK DOOR FRONT. OVERALL...HIGH TEMPERATURES ARE EXPECTED RANGE THROUGH THE UPR 70S TO LWR 80S EXCEPT UPR 60S TO LWR 70S NEAR THE COAST. LOWS RANGE FROM THE UPR 50S TO LWR 60S. && .AVIATION /08Z MONDAY THROUGH FRIDAY/... VFR CONDITIONS PREVAIL AS OF 06Z...TOO DRY FOR ANY FOG (ISOLATED SHALLOW GROUND FOG POSSIBLE IN COLDEST LOCATIONS BUT DOES NOT LOOK TO AFFECT TAF SITES). A BIT MORE WIND BY THIS AFTERNOON THAN PAST 2 DAYS...GENERALLY AROUND 10 TO 15 KNOTS FROM THE SW. OUTLOOK: SIMILAR CONDITIONS INTO TUE...DRY/MOSTLY SUNNY WITH S/SW WINDS. BY TUE EVENING/NIGHT THERE WILL BE THE POSSIBILITY OF A FEW SHOWERS/TSTMS AT KSBY...AND A CHANCE ACROSS MOST OF THE AREA BY WEDNESDAY AFTERNOON AND EVENING. WINDS GENLY SHIFT TO THE E/NE THU WITH CONTINUED VFR CONDITIONS OUTSIDE OF ANY ISOLATED CONVECTION. && .MARINE... SEAS NOW DOWN TO 3-4 FT ON THE OCEAN. SFC HIGH PRESSURE IS CENTERED ALONG/OFF THE NC COAST. SYNOPTIC PRESSURE GRADIENT TO REMAIN FAIRLY WEAK TODAY...ALTHOUGH IT WILL STRENGTHEN A BIT THIS AFTN/TONIGHT AS THE SFC HIGH BECOMES CENTERED OFF THE NC COAST WHILE LOW PRESSURE MOVES THROUGH QUEBEC. WHILE THERE WILL LIKELY BE SOME GUSTS TO 15-20 KT BY TONIGHT...THIS STILL LOOKS TOO MARGINAL TO RAISE ANY HEADLINES IN THE BAY AS MIXING WILL NOT BE OPTIMAL (VERY WARM AIRMASS OVER RELATIVELY COOL WATERS). SEAS IN NRN COASTAL WATERS BUILD TO AROUND 4 FT...2-3 FT FARTHER SOUTH. GRADIENT SLACKENS A BIT ON TUE...THEN INCREASES TUE NIGHT/EARLY WED AS A BACKDOOR COLD FRONT APPROACHES FROM THE N. THE FRONT LOOKS TO GRADUALLY PUSH INTO THE AREA ON WED AND DISSIPATE WED NIGHT AS SFC HIGH PRESSURE BUILDS IN FROM THE N. COMBINED WITH SFC LOW OFF THE GA/SC CST THERE COULD POTENTIALLY BE SOME INCREASE IN WIND SPEEDS AS DIRECTIONS SHIFT TO THE E/NE. WHILE LATEST WAVEWATCH GUIDANCE SHOWS INCREASE IN SEAS FOR LATER THU INTO FRI...CURRENT TRACK OF SFC LOW STAYS TOO FAR SOUTH TO BRING ANY SIGNIFICANT INCREASE IN SEAS AND WINDS TO THE LOCAL AREA (WILL CONTINUE TO MONITOR TRENDS). && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...NONE. NC...NONE. VA...NONE. MARINE...NONE. && $$ SYNOPSIS...ALB/BMD NEAR TERM...BMD SHORT TERM...BMD LONG TERM...LSA AVIATION...LKB/DAP MARINE...LKB

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