Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 010205 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 1005 PM EDT FRI OCT 31 2014 .SYNOPSIS... WEAK HIGH PRESSURE WILL SLOWLY DISSIPATE ACROSS THE REGION THROUGH TONIGHT. A STRONG LOW PRESSURE SYSTEM WILL DEVELOP OFF THE MID ATLANTIC COAST SATURDAY AND SATURDAY NIGHT BEFORE EXITING THE AREA ON SUNDAY. HIGH PRESSURE RETURNS FOR THE BEGINNING OF NEXT WEEK. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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UPDATE...LOW LEVELS ARE SLOWLY SATURATING IN THE EASTERN PIEDMONT AS TEMP/DEWPOINT OBS COME IN WITHIN 5 DEGREES OR LESS OF EACH OTHER. BEST RAIN SHOWERS ARE CURRENTLY LOCATED ALONG INTERSTATE 81...SOUTH OF 460 AND EAST OF I-77...AND ARE SLOWLY MOVING ENE. RAINFALL SHOULD FINALLY MOVE INTO THE PIEDMONT AFTER MIDNIGHT. TEMPS HAVE FALLEN INTO THE LOWER 40S ACROSS PORTIONS OF SOUTH CENTRAL VA WHERE A PERIOD OF CLEAR SKIES EARLIER THIS EVENING HELPED TO PROMOTE RADIATIONAL COOLING. TEMPS HERE ARE STARTING TO LEVEL OFF (AS PER PREVIOUS DISCUSSION) DUE TO INCREASING CLOUD COVER STREAMING IN FROM THE SW. ASIDE FROM A FEW MINOR ADJUSTMENTS TO TEMPS/DEWPOINTS/POPS WITHIN THE NEXT FEW HOURS...THE OVERALL FORECAST FOR TONIGHT IS ON TRACK. PREVIOUS DISCUSSION (403 PM)...THE LATEST SURFACE ANALYSIS SHOWS WEAK HIGH PRESSURE OVER THE PIEDMONT...WITH A 1005MB AREA OF LOW PRESSURE OFF THE NC OUTER BANKS...WHICH HAS FORMED IN RESPONSE TO A SHORTWAVE TROUGH PUSHING OFF THE SOUTHEAST COAST. A STRONGER SHORTWAVE TROUGH LAGS BACK OVER THE SRN GREAT LAKES AND THIS WILL BECOME THE PRIMARY FEATURE INTO SAT. THE LEADING WAVE WILL CONTINUE TO PULL TO THE NE TONIGHT...AS THE STRONGER WAVE CONTINUES TO DIG SSE ACROSS THE LOWER OHIO VALLEY. OVERALL DRY CONDITIONS ARE EXPECTED...WITH INCREASING MID/HIGH CLOUDS (ONCE AFTERNOON CU DISSIPATE) AS THE LOCAL AREA REMAINS IN A REGION OF SUBSIDENCE BETWEEN THE TWO SYSTEMS. 12Z HIGH-RES DATA DOES INDICATE SOME MOISTURE COULD BACK INTO THE LOWER MD ERN SHORE LATE TONIGHT SEEMINGLY RELATED TO A NE FETCH ASSOCIATED WITH A COLD CONVEYOR BELT. A HIGH CHC TO LOW END- LIKELY (50-60%) PROBABILITY HAS BEEN INCLUDED LATE TONIGHT TO ACCOUNT FOR THIS. TEMPERATURES SHOULD DROP INTO THE LOW/MID 40S LATE THIS EVENING...WHICH SHOULD BE THE EVENTUAL OVERNIGHT LOWS AS TEMPERATURES BECOME STEADY AFTER MIDNIGHT.
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&& .SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/... THE OVERALL FORECAST SCENARIO REMAINS SIMILAR. A STRONG SHORTWAVE TROUGH WILL DIG ACROSS THE TENNESSEE VALLEY TONIGHT AND ACROSS THE CAROLINAS SAT. GOOD AGREEMENT CONTINUES WITH RESPECT TO A CLOSED UPPER LOW FORMING OFF THE CAROLINA COAST MIDDAY SAT...WITH SURFACE CYCLOGENESIS OFF THE OUTER BANKS SAT AFTERNOON/EVENING. THE SURFACE LOW WILL QUICKLY LIFT TO THE NE LATER SAT NIGHT INTO SUNDAY...WITH ~1032MB SURFACE HIGH PRESSURE BUILDING IN FROM THE NW THROUGH SUN NIGHT. THE AFOREMENTIONED AREA OF SUBSIDENCE SHOULD REMAIN OVER THE AREA (WITH THE EXCEPTION OF THE ERN SHORE AND FAR SW PIEDMONT) THROUGH MIDDAY SAT. THE CHC OF RAIN THEN INCREASES SAT AFTERNOON ACROSS NE NC/SE VA AS THE LOW DEVELOPS OFF THE COAST. OVERALL QPF AMOUNTS WILL BE MINIMAL AND GENERALLY LESS THAN 0.25IN. THE HIGHEST AMOUNTS (0.25-0.50IN) SHOULD BE ACROSS THE ERN SHORE WHERE THE DURATION OF RAIN SHOULD BE LONGEST. A PERIOD OF STRONG NNE WIND (25-35 MPH WITH GUSTS TO ~45MPH) IS EXPECTED ALONG COASTAL ZONES AS THE LOW DEEPENS OFF THE COAST AND STRONG CAA COMMENCES. AREAS OF MINOR TIDAL FLOODING ARE POSSIBLE ALONG THE ATLC BEACHES AND LWR CHES BAY (SEE COASTAL FLOODING SECTION BELOW). A WIND ADVISORY MAY BE NEEDED OVER AT LEAST SOME OF THE COASTAL ZONES SAT NIGHT FOR A 6-10 HOUR PERIOD. THIS WILL REMAIN HIGHLIGHTED IN THE HWO AT THIS TIME. RAIN WILL TAPER OFF SAT NIGHT WITH SUBSIDENCE IN THE WAKE OF THE DEPARTING WAVE. THE SKY CLEARS OUT QUICKLY INTO SUNDAY MORNING (ALTHOUGH A BAND OF SC COULD DEVELOP OFF THE BAY SUNDAY DUE TO THE COOLER DRIER AIR ADVECTING OVER SSTS ~62-64F). THE SURFACE HIGH OF CANADIAN ORIGIN SINKS FROM THE OHIO VALLEY INTO THE SOUTHEAST BEGINNING SUNDAY. THIS WILL USHER IN THE COOLEST AIR OF THE SEASON TO DATE. HIGHS SUNDAY SHOULD RANGE FROM AROUND 50 N/NE...TO THE MID 50S S. THE FIRST WIDESPREAD FREEZE OF THE SEASON SHOULD OCCUR LATE SUN NIGHT/EARLY MON MORNING AS LOWS DROP TO 28-32 OVER THE INTERIOR COASTAL PLAIN AND PIEDMONT. ENOUGH SFC PRESSURE GRADIENT WILL LIKELY LINGER CLOSER TO THE COAST...WHICH WILL KEEP LOWS IN THE MID/UPPER 30S. THE HIGH SHIFTS OFFSHORE MONDAY...WITH SSW FLOW RESUMING ACROSS THE REGION. HIGHS SHOULD REBOUND INTO THE UPPER 50S/MID 60S UNDER A MOSTLY SUNNY SKY. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... MEDIUM RANGE PERIOD CHARACTERIZED BY GENERAL MODERATION OF TEMPERATURES TO BEGIN THE PERIOD AS HIGH PRESSURE SLIDES OFF THE SOUTHEAST COAST TUESDAY/EARLY WEDNESDAY WITH RESULTANT SOUTH-SOUTHWEST FLOW ALLOWING MAXIMA TO REBOUND INTO THE 60S TO LOWER 70S TUESDAY AND WEDNESDAY, WITH EARLY MORNING LOWS MODERATING BACK INTO THE 40S TO NEAR 50 WED AND THU MORNING. ALOFT, UPPER PATTERN WILL BE CHARACTERIZED BY UPPER RIDGING, WHICH WILL GRADUALLY BREAK DOWN AND SLIP OFFSHORE LATE WED/THU. NORTHERN STREAM DISTURBANCE TRAVERSING THE CANADIAN PRAIRIES INTO THE UPPER GREAT LAKES DURING THE MIDWEEK PERIOD, WITH THE ASSOCIATED WEAK SURFACE FRONT DROPPING INTO THE AREA BY LATE WED NGT/THURSDAY. ONCE AGAIN, THE BEST FORCING/DYNAMICS LOOK TO REMAIN CONFINED TO THE NORTH/NORTHEAST. THEREFORE, SUSPECT THE FROPA WILL ONCE AGAIN HAVE LITTLE MOISTURE WITH WHICH TO WORK. WILL KEEP POP NO HIGHER THAN 20% FOR WED/THU...WITH ONLY A SLIGHT DROP OFF IN TEMPERATURE POST FRONTAL LATE IN THE INTO THE 60S, WITH EARLY MORNING LOWS NEAR CLIMO VALUES FRIDAY AND SAT MORNINGS. && .AVIATION /02Z SATURDAY THROUGH WEDNESDAY/... THE REGION IS BETWEEN SYSTEMS AS OF 00Z. SEVERAL WAVES OF LOW PRESSURE ARE SLIDING ALONG A STALLED FRONT OFF THE COAST WHILE A STRONG UPPER LEVEL DISTURBANCE CONTINUES TO MOVE SEWD THROUGH THE OHIO VALLEY. LOW PRESSURE OFF THE NORTH CAROLINA COAST WILL BEGIN TO DEVELOP OVERNIGHT AND INTO THE DAY ON SATURDAY. THIS WILL STRENGTHEN THE ONSHORE FLOW AND CLOUDS WILL DEVELOP AND LOWER TO MVFR/IFR LEVELS TOWARD SUNRISE SAT AND CONTINUING THROUGH THE DAY. AS THE LOW STRENGTHENS...EXPECT WINDS TO INCREASE TO 10 TO 15 KTS BY 12-15Z...INCREASING TO 20-25KT BY 18Z...WITH GUSTS TO AROUND 30 KT ALONG THE COAST. THE LOW WILL PULL AWAY FROM THE COAST AFTER 06Z SUN WITH VFR CONDITIONS BY 10Z...BUT GUSTY NW WINDS WILL LINGER THROUGH THE DAY ON SUNDAY. HIGH PRESSURE NUDGES INTO THE AREA SUNDAY NIGHT CONTINUING VFR CONDITIONS. && .MARINE...
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UPDATE...EXTENDED SCA FLAGS FOR THE SOUND AND SRN COASTAL WATERS FROM VA/NC BORDER TO CURRITUCK LIGHT UNTIL 1 AM AND 4 AM RESPECTIVELY. AS STRONGER WINDS SHIFT SWD OVER THIS TIME...SEAS WILL BE AROUND 5 FT. PREVIOUS DISCUSSION...LATEST OBS REFLECT N-NE WINDS THIS AFTN 10-15KT. SURFACE LOW PRESSURE HAS DEVELOPED ALONG THE STALLED COASTAL FRONT ORIENTED OFFSHORE. WINDS HV INCREASED TO LOW END/MARGINAL SCA CRITERIA THIS AFTN AND HAVE RAISED A SMALL CRAFT ADVY OVER THE LOWER BAY AND SOUND THROUGH EARLY THIS EVENING. WINDS SHOULD DIMINISH FOR THE MID EVENING HOURS INTO EARLY SAT AS SYSTEM PUSHES FARTHER NE AWAY FROM THE AREA AND FARTHER OFFSHORE... TO A POSITION OFF OF THE NEW ENGLAND COAST BY LATE TONIGHT. WINDS WL BE RAMPING UP AGAIN TOWARDS SUNRISE SAT MORNING, AS LOW PRESSURE DEVELOPS RAPIDLY NEAR HATTERAS. WINDS/WAVES/SEAS INCREASE AS THIS LOW PRES STRENGTHENS OFF THE NC CST SATURDAY IN RESPONSE TO A VERY POTENT MID-LEVEL SHORTWAVE TROF. SCA OVR NRN CSTL WTRS (ADDED PARRAMORE TO CAPE CHARLES LGT TO EXISTING SCA) REMAINS IN EFFECT FOR SATURDAY BEFORE THE GALE WARNING GOES INTO EFFECT SATURDAY NIGHT. A PERIOD OF 5 FT SEAS IS EXPECTED OVER THIS AREA, WHILE CONDITIONS ELSEWHERE OVER THE BAY AND LOWER JAMES LOOK TO DETERIORATE QUICKLY ENOUGH SAT AFTN TO WARRANT GOING DIRECTLY TO THE GALE HEADLINE.
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&& .TIDES/COASTAL FLOODING... LOW PRESSURE IS EXPECTED TO RAPIDLY STRENGTHEN OFF THE COAST LATE SATURDAY AFTERNOON INTO EARLY SUNDAY MORNING. STRONG NNW WINDS ARE LIKELY TO RESULT IN TIDAL DEPARTURES ON THE ORDER OF 1-2 FT ABOVE NORMAL SATURDAY NIGHT ALONG THE ATLANTIC COAST AND LOWER BAY. MINOR TIDAL FLOODING IS EXPECTED FOR THESE LOCATIONS AS THE SURGE APPEARS TO COINCIDE WITH THE HIGH TIDE CYCLE SATURDAY NIGHT/EARLY SUNDAY MORNING. && .AKQ WATCHES/WARNINGS/ADVISORIES...
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MD...NONE. NC...NONE. VA...NONE. MARINE...SMALL CRAFT ADVISORY FROM 1 PM EDT SATURDAY TO 11 PM EST SUNDAY FOR ANZ635>637. GALE WARNING FROM 4 PM EDT SATURDAY TO 7 AM EST SUNDAY FOR ANZ630>634-638. SMALL CRAFT ADVISORY UNTIL 1 AM EDT SATURDAY FOR ANZ633. SMALL CRAFT ADVISORY FROM 7 AM TO 4 PM EDT SATURDAY FOR ANZ650- 652-654. GALE WARNING FROM 4 PM EDT SATURDAY TO 4 PM EST SUNDAY FOR ANZ650-652-654-656-658. SMALL CRAFT ADVISORY UNTIL 4 AM EDT SATURDAY FOR ANZ658.
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&& $$ SYNOPSIS...AJZ/ALB NEAR TERM...AJZ/BMD SHORT TERM...AJZ/ALB LONG TERM...MAM AVIATION...ESS/DAP MARINE...MAM/DAP TIDES/COASTAL FLOODING...AKQ

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