Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 042010 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 410 PM EDT MON MAY 4 2015 .SYNOPSIS... HIGH PRESSURE WILL SLIDE FARTHER OUT TO SEA TONIGHT INTO WEDNESDAY. A BACKDOOR COLD FRONT APPROACHES FROM THE NORTH TUESDAY NIGHT...THEN DROPS INTO VIRGINIA WEDNESDAY INTO EARLY THURSDAY...BEFORE DISSIPATING. LOW PRESSURE WILL SPIN OFF OR NEAR THE SOUTHEAST COAST THURSDAY INTO FRIDAY. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... HI PRES CNTRD OFF THE MID ATLC CST WILL PROVIDE THE AREA WITH DRY AND MILD CONDITIONS TNGT. UNDER A CLEAR OR MOSTLY CLEAR SKY...MIN TEMPS WILL BE IN THE UPR 50S TO LWR 60S. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/... 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 NIGHT THROUGH MONDAY/... MEDIUM RANGE PERIOD HIGHLY DEPENDENT PERSISTENT UPPER RIDGE OVER THE EAST, AS WELL AS THE DEVELOPMENT AND EVENTUAL PROGRESS OF EXPECTED DEVELOPMENT OF AN AREA OF LOW PRESSURE OFF THE EAST COAST OF FLORIDA. MODELS ARE IN GENERAL AGREEMENT OF THE DEVELOPMENT AND INITIAL SLOW DRIFT NORTHWARD ON WEDNESDAY. THE HURRICANE CENTER IS CONTINUING TO MONITOR THIS FEATURE FOR POTENTIAL SUBTROPICAL DEVELOPMENT. SFC RIDGING TO THE NORTH AND W-NW FLOW ALOFT SHOULD FORCE THE LOW TO MEANDER AROUND A POSITION ALONG/JUST OFF THE SOUTHEAST COAST THROUGH THE WEEKEND. THE GEFS AND EURO ENSEMBLES BOTH CONTINUE TO TAKE THE LOW INLAND ALONG THE SC/GA COAST, AS DOES THE NEW 12Z/04 GFS. THE OPERATIONAL EUROPEAN, MEANWHILE CONTINUES TO KEEP THE SYSTEM OFFSHORE. A SOLUTION TOWARDS THE GFS REMAINS THE HPC PREFERENCE, AND HV EDGED THE FORECAST IN THIS DIRECTION. THIS SCENARIO WOULD YIELD SLIGHT CHC TO LOW CHC POP FOR MAINLY DIURNALLY DRIVEN SHOWERS/T-STORMS AT MOST ACROSS OUR AREA. LOWEST CHANCES WILL BE ACROSS THE NORTH WITH SFC RIDGING IN PLACE NORTH OF THE AREA. MAINTAINED LOW POPS (20-30%) WITH THE (SUBTROPICAL?) LOW STILL MEANDERING TO THE E-SE. OTHER HEADLINE FOR THE PERIOD WILL BE THE WARMER TEMPERATURES. E-SE FLOW WILL BRING A MODEST INCREASE IN HUMIDITY, AND INCREASING LOW LEVEL THICKNESSES FAVOR WARM HIGHS IN THE 80S UNDER A PARTLY TO MOSTLY SUNNY SKY. EARLY MORNING LOWS LOOK TO REMAIN WELL INTO THE 50S TO MID 60S LATE WEEK INTO EARLY NEXT WEEK. && .AVIATION /20Z MONDAY THROUGH SATURDAY/... HIGH PRESSURE IS CENTERED OFF THE MID ATLANTIC COAST. A COLD FRONT OVER THE GREAT LAKES SLOWLY APPROACHES THE REGION FROM THE N/NW THROUGH WEDNESDAY. AS OF 18Z...SCT CUMULUS WITH BASES AROUND 7-9 K FT COVERED THE CWA. WINDS WERE FROM THE S/SW AT AROUND 10 TO 15 KNOTS WITH A FEW HIGHER GUSTS. WINDS DIMINISH TO AROUND 5 TO 10 KNOTS BY EARLY EVENING AND REMAIN AT THOSE SPEEDS OVERNIGHT AND INTO TUESDAY MORNING. THE SKY WILL BE MOSTLY CLEAR BY SUNSET AND REMAIN THAT WAY THROUGH TUESDAY. OUTLOOK: THERE IS A CHANCE FOR TSTMS TUESDAY EVENING AT SBY. THERE WILL BE A DAILY CHANCE FOR MAINLY AFTN SHOWERS AND THUNDERSTORMS WEDNESDAY THROUGH SATURDAY...ESPECIALLY SOUTHERN PORTIONS. THEY ARE NOT EXPECTED TO BE WIDESPREAD. OTHERWISE MAINLY VFR CONDITIONS ARE EXPECTED DURING THE PERIOD. LATE IN THE WEEK...PATCHY FOG WILL BE PSBL AROUND SUNRISE. && .MARINE... LATEST OBS REFLECT S-SW FLOW 10-15KT ACROSS THE WATERS THIS AFTN W/SFC HIGH PRESSURE ORIENTED ALONG/OFF THE NC COAST. WINDS HAVE INCREASED INTO THE 10-15 KT RANGE AS PRESSURE GRADIENT HAS TIGHTEND SLIGHTLY IN RESPONSE TO LOW PRESSURE MOVES THROUGH QUEBEC AS HIGH PRESSURE REMAINS JUST OFFSHORE. STILL APPEARS AS IF THERE WILL LIKELY BE SOME GUSTS TO 15-20 KT BY TONIGHT...BUT SHOULD BE TOO INFREQUENT/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 3-4 FT...2-3 FT FARTHER SOUTH. GRADIENT SLACKENS A BIT ON TUE...THEN INCREASES TUE NIGHT/EARLY WED AS A COLD FRONT DROPS SOUTH ACROSS THE WATERS IN BACKDOOR FASHION. 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 PREVIOUSLY REFERENCED SFC LOW OFF THE SOUTHEAST COULD BRING A MODEST INCREASE IN WIND SPEEDS AS DIRECTIONS SHIFT TO THE E/NE THU WITH TIGHTENING PRES GRADIENT...AND HAVE CONTINUED WITH A GFS WEIGHTED GFS/CMC SOLUTION FOR THIS PERIOD. 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 THESE TRENDS AND ANY LINGERING COASTAL FLOOD THREATS OVER THE NEXT 24 TO 36 HRS. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...NONE. NC...NONE. VA...NONE. MARINE...NONE. && $$ SYNOPSIS...TMG NEAR TERM...TMG SHORT TERM...TMG LONG TERM...MAM AVIATION...LSA MARINE...MAM

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