Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 040750 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 350 AM EDT FRI SEP 4 2015 .SYNOPSIS...
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A BACKDOOR COLD FRONT WILL MOVE SOUTH ACROSS THE AREA LATER TODAY AND TONIGHT. STRONG HIGH PRESSURE ACROSS THE NORTHERN STATES WILL SLOWLY BUILD SOUTH ACROSS THE MID ATLANTIC REGION SATURDAY AND SUNDAY. LOW PRESSURE DEVELOPS OFF THE SOUTHEASTERN COAST LATE IN THE WEEKEND.
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&& .NEAR TERM /TODAY/...
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KEPT PTCHY FOG IN GRIDS THRU 12Z PER CRNT SFC OBS. MODELS AGREE IN BUILDING AN UPR LEVEL RIDGE OVER THE NERN CONUS THRU THE HOLIDAY WEEKEND. LARGE SCALE CONFLUENCE OVER ERN CANADA ALLOWS STRONG SFC HIGH PRESSURE TO BUILD INTO NEW ENGLAND...PUSHING A BACKDOOR FRONT ACROSS THE FA LATER TODAY. BEFORE THIS OCCURS... ANTHR SUMMER-LIKE DAY WITH TMPS ABT +1 STD DEV ABOVE NORMAL. XPCT PARTLY TO MOSTLY SUNNY SKIES WITH HIGHS RANGING FROM THE M80S ALONG THE COAST (WHERE WNDS WILL GRADUALLY TURN NE) TO THE U80S-L90S WEST OF CHES BAY. A WARM/MOIST AND MODERATELY UNSTABLE AIR MASS (MLCAPE VALUES 1000- 1500 J/KG) WILL REMAIN OVR THE FA IN ADVANCE OF THE BKDR COLD FRONT. A MORE STABLE AIRMASS PROGGED ALONG THE COAST DUE TO THE ONSHORE FLOW. HIGH RES DATA SUGGESTS A DRY MORNING THEN A RTHR QUICK BUILDUP IN CU/TCU/SCT CB`S AS THE CONVECTIVE TMPS ARE REACHED ARND NOON. MODELS SHOW BEST SPRT FOR CONVECTION WILL BE ALONG AND WEST OF THE I95 CORRIDOR (ALONG A WEAK WND CONVERGENCE BNDRY) WITH LITTLE IF ANY SPRT EAST OF THE CHES BAY. THUS...KEPT POPS BLO 14% ALONG THE COAST...20-30 POP FROM THE CHES BAY WEST TO THE I95 CORRIDOR WITH 40- 50 POP ACROSS THE PIEDMONT. NO SVR WX XPCT...BUT CUD SEE GUSTY WNDS AND LCLLY HVY DOWNPOURS GIVEN PW`S AOA 1.5 INCHES.
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&& .SHORT TERM /TONIGHT THROUGH SUNDAY/...
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FRONT PUSHES SOUTH ACROSS THE REGION THIS EVENING BEFORE WEAKENING INTO A ELONGATED TROF OFF THE CAROLINA COAST IVOF THE GULF STREAM WALL. THUS...KEPT THUNDER CHCS ACROSS THE PIEDMONT THRU 00Z. AIRMASS BECOMES MORE STABLE BY LATE EVE AND OVERNIGHT...HOWEVER THE COMBO OF LINGERING MSTR AT DIFFERENT LEVELS AND THE INCRG NE WND FLOW LEADS TO THE NEED TO KEEP AT LEAST SLGHT CHC POPS GOING THRU THE NIGHT UNDER PT TO MSTLY CLDY SKIES. BCMG BREEZY AT THE COAST AS WELL WITH GUSTS UP TO 25 MPH. HIGHEST POPS LATE TONIGHT SHIFTS TOWARD THE COAST DUE TO THE MOIST FLOW OFF THE OCEAN. LOWS U60S-L70S. WHAT ONCE LOOKED LIKE A DRY AND COOLER WEEKEND NOW APPEARS TO BE RTHR UNSETTLED DUE TO LTL MOVEMENT IN SYNOPTIC FEATURES. ADD TO THAT A DVLPNG AREA OF LOW PRS OFF THE SERN COAST RESULTS IN PERIODS OF LOW LEVEL CLOUDINESS AND A RTHR GUSTY NE WIND ALONG THE COAST (25-30 MPH). LTST DATA ALSO SUGGESTS WEAK MID LVL DISTURBANCES TRACKING ACROSS THE REGION RESULTING IN THE NEED TO KEEP 20-40 POP ACROSS THE SRN HALF OF THE FA SAT. DRIEST ACROSS THE NORTH CLOSER TO THE CENTER OF THE HIGH. COOLER GIVEN THE ABOVE SCENARIO WITH HIGHS U70S-L80S. PCPN CHCS (20-40%) CONT TO SHIFT TOWARDS THE COAST SAT NIGHT AS THE HIGH PRS EXTENDS SW ACROSS THE MTS KEEPING THW WRN HALF OF THE FA DRY. LOWS SAT NIGHT M60S-L70S. MSTR FROM THE CSTL TROF AND THE PERSISTENT ONSHORE FLOW WILL LIKELY LEAD TO ADDNTL SHWRS (20-40 POP) MOVG ONSHORE AND MAKING AS FAR WEST AS THE I95 CORRIDOR SUNDAY BEFORE SHIFTING TOWARDS THE COAST ONCE AGAIN SUNDAY NIGHT. HIGHS SUNDAY U70S-L80S.
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&& .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... LONG TERM PERIOD STARTS OFF SUN NGT AND MON WITH SFC LO PRES SPINNING OFF THE CAROLINA CST WITH HI PRES N AND W OF THE FA. RESULTANT ONSHORE FLOW WILL LEAD TO TEMPS ONLY MAKING IT INTO THE MID 80S MON UNDER A PRTLY-MSTLY SKY. WITH THE MOIST ONSHORE FLOW DID HOLD ONTO SOME SLGT CHANCE-CHANCE POPS OVER MUCH OF THE FA SUN NGT/MON. KEPT THUNDER OUT DUE TO A LACK OF INSTABILITY. THE SFC LO WEAKENS AND STARTS SLIDING E TUE ALLOWING FOR DRIER CONDS AND TEMPS REBOUNDING INTO THE MID/UPR 80S UNDER A PRTLY CLOUDY SKY. DRY WX CONTINUES MIDWEEK WITH TEMPS FURTHER INCREASING AS SLY FLOW DEVELOPS AHEAD OF THE NEXT COLD FRNT...WITH HI TEMPS IN THE UPR 80S TO NR 90 WED AND THUR. THE FRNT WILL CROSS THE AREA SOMETIME LATE THU OR FRI. && .AVIATION /08Z FRIDAY THROUGH TUESDAY/... AREAS OF MVFR FOG/HAZE EXPECTED EARLY THIS MORNING...WITH A CHC FOR BRIEF IFR VSBYS AT KPHF AND KECG BETWEEN 09Z-12Z. OTW...VFR CONDITIONS TO CONTINUE TODAY OUTSIDE OF ISOLD TO WDLY SCT AFTN CONVECTION...MAINLY ALONG AND WEST OF INTERSTATE 95. OUTLOOK...PERIODS OF SUB VFR CONDITIONS WILL OCCUR IN AREAS OF SHOWERS AND IN EARLY MORNING FOG/STRATUS SATURDAY THRU MONDAY WITH ONSHORE FLOW. IN ADDITION...GUSTY WINDS ARE EXPECTED ALONG THE COAST ON SATURDAY. && .MARINE...
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A WEAK TROUGH OF LOW PRESSURE OVER THE WATERS THIS MORNING IS PRODUCING LIGHT N-NW WINDS. NE FLOW DEVELOPS ALL WATERS BY LATE MORNING/AFTN AS A BACKDOOR COLD FRONT DROPS SOUTH TOWARDS THE REGION AND HIGH PRESSURE OVERSPREADS THE NE STATES. WINDS WILL SLOWLY INCREASE THRU THE DAY OVER ALL WATERS...REACHING 10-15 KT EVERYWHERE BY EARLY EVENING AND 15-20 KT OVER THE NORTHERN OCEAN ZONES. WINDS INCREASE A BIT MORE FRIDAY NIGHT SO THAT SCA`S WILL BE NECESSARY FOR THE OCEAN/BAY/LOWER JAMES RIVER...WITH WAVES ON THE BAY BUILDING TO 3-4 FT AND SEAS REACHING 4-6 FT (HIGHEST NORTH). THE START TIME OF THE SCA FOR THE SOUTHERN COASTAL WATERS (SOUTH OF CAPE CHARLES) WAS PUSHED BACK ABOUT 12 HRS (TIL 7AM SAT) AS IT WILL TAKE THE LONGEST FOR SCA CONDITIONS TO BE REALIZED THERE. ALL SCA`S WILL THEN RUN THROUGH THE DAY SAT. MAY ALSO NEED TO INCLUDE THE CURRITUCK SOUND DURING THE DAY SAT BUT NOT CONFIDENT ENOUGH ATTM DUE TO SHORT DURATION OF HIGHEST WINDS. CONDITIONS IMPROVE SAT NIGHT FOR MOST OF THE BAY AND LOWER JAMES SO THAT THE SCA`S CAN END. STILL EXPECTING WAVES TO REMAIN AROUND 4FT AT THE MOUTH OF THE BAY INTO SUNDAY MORNING...WITH SEAS LINGERING AROUND 5 FT. SUB-SCA CONDITIONS APPEAR LIKELY TO START NEXT WEEK. IN ADDITION...THE ONSHORE FLOW AND HIGH NEARSHORE WAVES WILL ENHANCE THE RIP CURRENT THREAT FOR THE HOLIDAY WEEKEND.
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&& .AKQ WATCHES/WARNINGS/ADVISORIES...
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MD...NONE. NC...NONE. VA...NONE. MARINE...SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 7 AM EDT SUNDAY FOR ANZ634. SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 1 AM EDT SUNDAY FOR ANZ632. SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 10 PM EDT SATURDAY FOR ANZ630-631. SMALL CRAFT ADVISORY FROM 1 AM TO 10 PM EDT SATURDAY FOR ANZ638. SMALL CRAFT ADVISORY FROM 1 AM SATURDAY TO 7 AM EDT SUNDAY FOR ANZ654. SMALL CRAFT ADVISORY FROM 7 AM SATURDAY TO 7 AM EDT SUNDAY FOR ANZ656-658. SMALL CRAFT ADVISORY FROM 7 PM THIS EVENING TO 7 AM EDT SUNDAY FOR ANZ650-652.
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&& $$ SYNOPSIS...MPR NEAR TERM...MPR SHORT TERM...MPR LONG TERM...MAS AVIATION...JDM MARINE...JDM

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