Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 121736 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 136 PM EDT SAT JUL 12 2014 .SYNOPSIS... HIGH PRESSURE WEAKENS ACROSS THE AREA THROUGH THE WEEKEND. LOW PRESSURE MOVES ACROSS THE GREAT LAKES REGION WITH THE TRAILING COLD FRONT APPROACHING FROM THE NORTHWEST EARLY NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... ***NWS SURVEY TEAM CONFIRMS BOTH AN EF-0 TORNADO AND STRAIGHT LINE WINDS IN VIRGINIA BEACH*** (SEE PNSAKQ FOR DETAILS) ***NWS CONFIRMS STRAIGHT LINE WIND DAMAGE IN THE CAPRON AREA AND ACROSS SOUTHAMPTON COUNTY*** LATEST ANALYSIS SHOWING WEAK SFC HIGH PRESSURE CENTERED OVER SE VA AND THE DELMARVA...WITH LOW PRESSURE DEEPENING ACRS THE MID/UPPER MS VALLEY. FLOW ALOFT IS WNW...AND LARGE MCS EVIDENT ON RADAR OVER IL/IN. EARLY AM FOG HAS BURNED OFF LEAVING VARIABLY CLOUDY SKIES ACRS THE LOCAL AREA...TRENDING TOWARDS MOSTLY CLEAR INTO THE EARLY AFTN AS LOW LEVEL MOISTURE AND CLOUDS MIX OUT AND HIGH CLOUDS OVER CENTRAL ASSOCIATED W/ A DEPARTING SHORTWAVE MOVE SE AND PUSH OFF THE COAST. CURRENT DEW PTS ARE A LITTLE HIGHER THAN GUIDANCE RIGHT NOW (UPPER 60S TO LOWER 70S) BUT THINK THEY WILL STILL DROP INTO THE MID-UPPER 60S THROUGH THE AFTN W/ MIXING. HAVE ADJUSTED POPS LATER THIS AFTN...REMOVING THEM ACRS NE NC CLOSER TO SFC HIGH PRESSURE AND MORE STABLE CONDITIONS. HOWEVER...HAVE ADDED MENTION FOR ISOLATED TSTMS AFTER 19Z ACRS THE FAR NW COUNTIES DUE TO UPSLOPE LOW LEVEL FLOW POSSIBLY LEADING TO SOME DEVELOPMENT OVER THE APPALACHIANS AND DRIFTING EAST INTO THE AKQ CWA LATE. HAVE ALSO BUMPED UP MID- LATE AFTN CLOUD COVER ALONG/WEST OF I-95 FOR SKIES TO AVG PARTLY SUNNY...WHILE MOSTLY SUNNY CONDITIONS SHOULD PREVAIL FARTHER EAST. HIGHS AVG 80-85 F NEAR THE COAST...AND IN THE UPPER 80S TO AROUND 90 F FARTHER INLAND. FOR TONIGHT...WILL HAVE A 20% POP ACRS THE FAR NW INTO THE MID EVENING HRS...THEN DRY/PARTLY CLOUDY N TO MOSTLY CLEAR S. LOWS MAINLY 65-70 F. OVERALL...EXPECT LESS FOG THAN PAST 2 NIGHTS AS LOW LEVEL FLOW SHIFTS MORE TO THE S/SW (SOME PATCHY FOG POSSIBLE MAINLY OVER INTERIOR SE VA/NE NC). && .SHORT TERM /SUNDAY THROUGH MONDAY/... HOT WX RETURNS ON SUNDAY. NEXT S/W PROGGED TO MOVE ACROSS THE GREAT LAKES AND NE STATES WITH A SFC THERMAL TROF PROGGED EAST OF THE MTS DURING THE AFTN. HOWEVER...RISING HEIGHTS ALOFT LOOKS TO CAP THE ATMOSPHERE FOR THE MOST PART SO WILL ONLY CARRY SLIGHT CHC POPS (~20%) AT MOST FOR AFTN TSTMS WELL INLAND AND OVER THE NORTH...KEEPING IT DRY ACRS SE VA/NE NC. HIGHS LOW-MID 90S...EXCEPT M80S AT THE BEACHES. FLOW TURNS TO THE SSW IN EARNEST ON MON AHEAD OF AN APPROACHING COLD FRONT...WITH INCREASING MOISTURE AND BUILDING HEAT. ENOUGH INSTABILITY PROGGED FOR SCTD AFTN TSTMS ALL AREAS (30-40% POPS)... EXCEPT NC OUTER BANKS WHERE A 20% POP WILL BE MAINTAINED. HIGHS 90-95...EXCEPT MID 80S AT THE BEACHES. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... HIGHLY ANOMALOUS FLOW WILL DEVELOP OVER THE CONUS DURING THE MEDIUM RANGE...AS A STRONG CLOSED LOW DROPS OVER THE GREAT LAKES REGION. THE RESULT WILL BE BELOW NORMAL TEMPS AND WET CONDITIONS FROM THE UPPER MIDWEST TO THE OH VALLEY. HOWEVER...THE LOCAL AREA REMAINS SEASONABLY WARM AS MUCH OF THE COOLER AIR WILL BE LOCKED WEST OF THE CNTRL APPALACHIANS. AS AN ANOMALOUS TROUGH DEVELOPS OVER THE ERN CONUS...HEIGHT FALLS AND INCREASE WINDS ALOFT WILL RESULT IN BETTER FORCING FOR ASCENT OVER THE LOCAL AREA. WITH A WARM/MOIST AIRMASS ALREADY IN PLACE (MODEL DERIVED PRECIP WATERS ~ 2+ INCHES)...EXPECT BETTER COVERAGE OF SHOWERS/THUNDERSTORMS MON AFTERNOON ALONG A SHARPENING LEE/THERMAL TROUGH. HOWEVER...THE BEST DYNAMICS WILL REMAIN WEST OF THE LOCAL AREA ALONG THE COLD FRONT...SO THE BEST CHANCES WILL BE IN THE NORTH AND WEST. ANOTHER AREA OF SHOWERS/THUNDERSTORMS WILL LIKELY DEVELOP ALONG THE TROUGH/BOUNDARIES...CLOSEST TO THE BEST INSTABILITY. HIGHS TUE EXPECTED IN THE LOW 90S WITH DEW POINTS IN THE NEAR 70. STRONG SPEED MAX ROUNDS THE DEEP CLOSED LOW OVER THE GREAT LAKES TUES...EJECTING THE LOW NEWD INTO SE CANADA. THE COLD FRONT DROPS INTO THE REGION TUES NIGHT. STRONGEST DYNAMICS LIFT WELL NORTH OF THE REGION WITH THE CLOSED LOW...BUT HEIGHT FALLS AND PERTURBATIONS IN THE WSW FLOW WILL RESULT IN SCT-NUMEROUS SHOWERS/THUNDERSTORMS. STRONG TO SEVERE THUNDERSTORMS ALSO POSSIBLE AS MODELS DEPICT MARGINAL SHEAR AND MLCAPE > 2000 J/KG. ANOMALOUS TROUGH WILL PUSH THE SRN PORTION OF THE FRONT INTO THE DEEP SOUTH...BUT THE ERN PORTION LIKELY STALLING OVER/OFF THE MID-ATLANTIC COAST AS AN ANOMALOUS UPPER RIDGE REMAINS PARKED OVER THE WRN ATLANTIC. WILL MAINTAIN SLIGHT CHANCE-CHANCE POPS WEDS ACROSS THE SE AS THE FRONT WILL LIKELY LINGER OVER THE REGION. SFC HIGH PRESSURE WILL BE SLOW TO BUILD INTO THE REGION IN WAKE OF THE FRONT AS UPPER TROUGH REMAINS OVER THE ERN CONUS. BUT...WITH THE STALLED BOUNDARY ACROSS THE SE AND A PASSING SHORTWAVE TROUGH...SHOWERS AND THUNDERSTORMS MAY BE POSSIBLE NEXT WEEKEND. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/...
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SURFACE HIGH PRESSURE CONTS TO DOMINATE THE REGION WITH VFR CONDS AND LIGHT E-SE WNDS. EXPECT VFR CONDS THRU THE AFTN AND EVENING WITH NO EXPECTED FLIGHT HAZARDS. THERE IS THE SLIGHT CHC OF AN ISOLD TSTM DEVELOPING WEST OF RIC IN THE HIGHER ELEVATIONS DURING THE LATE AFTN/EVENING HOURS. WNDS WILL SHFT TO THE S-SW BY EARLY SUNDAY AS THE HIGH MOVES OFFSHORE. SHIFTING WNDS AND GOOD SUN TODAY WILL REDUCE CHC OF DENSE FOG IN THE MORNING ALTHO THERE IS A CHC FOR PTCHY MVFR FOG IN THE EARLY MORNING. DRY WEATHER CONTINUES INTO SUNDAY WITH THE HIGH OFFSHORE AND LOW PRESSURE TRACKING WELL NW OF THE LOCAL AREA. A COLD FRONT WILL BRING THE POTENTIAL FOR SHRA/TSRA MONDAY AND TUESDAY.
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&& .MARINE... LIGHT E/SE FLOW AOB 10KT SHOULD PREVAIL TODAY AS HIGH PRESSURE DRIFTS OFF THE NEW ENGLAND COAST. THE WIND WILL SHIFT TO S TONIGHT AS THE HIGH SETTLES OFF THE COAST...AND THEN SSW SUNDAY INTO MONDAY WITH HIGH PRESSURE ANCHORED OFF THE COAST. SPEEDS SHOULD INCREASE SUNDAY NIGHT INTO MONDAY AND AVERAGE 15-20KT OVER THE OCEAN AND 10-15KT BAY/SOUND/RIVERS. A COLD FRONT APPROACHES FROM THE NW MONDAY NIGHT. 12/00Z GFS IS FASTER THAN THE 12/00Z NAM (THROUGH 84HR) AND THE 12/00Z ECMWF/CMC. THE CURRENT FORECAST WILL FOLLOW MORE TOWARD THE 00Z ECMWF FOR WIND DIRECTION/FRONTAL TIMING. THIS WILL ALLOW THE WIND TO REMAIN SSW THROUGH TUESDAY NIGHT...BEFORE SHIFTING TO NORTHERLY WEDNESDAY. HIGH PRESSURE BUILDS OVER THE AREA BEHIND THE FRONT WITH THE WIND BECOMING LIGHT AND VARIABLE. SEAS SHOULD AVERAGE 2-3FT THROUGH SUNDAY WITH 1-2FT WAVES IN THE BAY. THE PERSISTENT (AND ENHANCING) SSW WIND SHOULD BUILD SEAS TO 3-4FT N SUNDAY NIGHT INTO MONDAY...WITH PERHAPS A PERIOD OF ~5FT FAR N BY MONDAY NIGHT. SEAS SHOULD REMAIN 2-3FT ACROSS THE SRN COASTAL ZONES. WAVES IN THE BAY SHOULD AVERAGE 2-3FT SUNDAY NIGHT THROUGH MONDAY NIGHT. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...NONE. NC...NONE. VA...NONE. MARINE...NONE. && $$ SYNOPSIS...LKB NEAR TERM...LKB SHORT TERM...JDM/LKB LONG TERM...SAM/DAP AVIATION...AJZ/JEF MARINE...AJZ

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