Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 140827 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 427 AM EDT MON APR 14 2014 .SYNOPSIS...
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HIGH PRESSURE REMAINS OFF THE MID ATLANTIC COAST TODAY. A STRONG COLD FRONT APPROACHES FROM THE WEST MONDAY NIGHT AND CROSSES THE REGION TUESDAY. CANADIAN HIGH PRESSURE BUILDS IN FROM THE NORTHWEST TUESDAY NIGHT AND SETTLES OVER THE MID ATLANTIC AND NORTHEAST WEDNESDAY.
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&& .NEAR TERM /THROUGH TONIGHT/...
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THE CURRENT UPPER AIR ANALYSIS PER GOES WV IMAGERY INDICATES AN AMPLIFIED LONGWAVE PATTERN FEATURING A STRONG UPPER RIDGE OVER THE WESTERN ATLANTIC...WITH A DEEP POTENT TROUGH DIGGING ACROSS THE CENTRAL PLAINS. AT THE SURFACE...HIGH PRESSURE REMAINS ANCHORED OFF THE COAST...WITH A 995MB LOW OVER NRN IL AND A COLD FRONT TRAILING BACK THROUGH THE MID-MISSISSIPPI VALLEY. THE HIGH OFF THE COAST REMAINS THE DOMINANT FEATURE TODAY...WITH INCREASING UPPER LEVEL MOISTURE IN DEEP LAYER SSW FLOW PRODUCING INCREASING/THICKENING HIGH CLOUDS. SCT AFTERNOON CU SHOULD DEVELOP AS WELL...SO THE SKY CONDITION SHOULD LARGELY PROGRESS FROM PARTLY SUNNY TO MOSTLY CLOUDY. TEMPERATURES WILL REMAIN WARM...WITH HIGHS RANGING FROM THE UPPER 70S TO AROUND 80 (LOCALLY COOLER ALONG THE ATLANTIC COAST OF THE EASTERN SHORE). A S WIND OF 15-20 MPH...WITH GUSTS TO 25-30 MPH SHOULD PREVAIL FROM LATE MORNING THROUGH THE AFTERNOON. FORCING ASSOCIATED WITH THE GREAT LAKES LOW SHOULD REMAIN WELL NW OF THE LOCAL AREA...SO ANY SHRA WILL LIKELY HOLD OFF UNTIL TONIGHT. THE PLAINS TROUGH ADVANCES EASTWARD INTO THE MID-MISSISSIPPI VALLEY TONIGHT. GENERAL MODEL CONSENSUS INDICATES A WEAK SHORTWAVE TROUGH LIFTING NNE AHEAD OF THE MAIN TROUGH. THIS SHOULD COMBINE WITH INCREASING WARM/MOIST ADVECTION AND RESULT IN AN INCREASING CHC OF SHRA ESPECIALLY AFTER MIDNIGHT. OVERNIGHT LOWS WILL BE VERY MILD AND GENERALLY IN THE LOW/MID 60S.
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&& .SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
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THE SITUATION BECOMES QUITE INTERESTING BY TUESDAY AFTERNOON. THE PRIMARY TROUGH LIFTS THROUGH THE TENNESSEE AND OHIO VALLEYS TUESDAY MORNING AND BEGINS TO TAKE ON A NEGATIVE TILT AS IT APPROACHES THE MID-ATLANTIC TUESDAY AFTERNOON. MEANWHILE...THE SURFACE COLD FRONT APPROACHES THE REGION FROM THE NW DURING THE DAY...WITH INCREASING LOW-LEVEL FRONTOGENESIS. 14/00Z NAM/GFS EACH INDICATE STRONG VERTICAL ASCENT IN THE RRQ OF A STRENGTHENING UPPER JET OVER ERN CANADA AND THE NERN US. THE PROBABILISTIC APPROACH FROM THE 14/03Z SREF MEAN SHOWS A 50+ KT LLJ ACROSS THE REGION TUESDAY (+3-4 ST DEV) AND THE DETERMINISTIC NAM/GFS (DESPITE SOME SPATIAL DIFFERENCES) EACH INDICATE THE POTENTIAL FOR THIS TO REACH 60-65KT. 0-3KM BULK SHEAR IS PROGGED TO REACH 50KT BY TUESDAY AFTERNOON ACROSS PORTIONS OF THE LOCAL AREA...WITH FORECAST HODOGRAPHS DEMONSTRATING CLOCKWISE CURVATURE FROM 0-3KM. THE NET RESULT IS A FAVORABLE SYNOPTIC/KINEMATIC ENVIRONMENT FOR STRONG TO SEVERE LINEAR CONVECTION. INSTABILITY IS PROGGED TO BE MINIMAL (DUE TO DEEP MOISTURE)...BUT WILL LIKELY BE THE DETERMINING FACTOR FOR STORM ORGANIZATION. IF THE ENVIRONMENT BECOMES MORE UNSTABLE THE LIKELIHOOD FOR EMBEDDED INTENSE CELLS AND BOWING SEGMENTS WILL INCREASE. OVERALL THE GREATEST THREAT FOR SEVERE STORMS APPEARS TO BE ACROSS SOUTHERN PORTIONS OF THE AREA...WITH THE MARINE ENVIRONMENT LIMITING SEVERE POTENTIAL OVER THE EASTERN SHORE. MODERATE TO HEAVY RAIN WILL ACCOMPANY THE CONVECTION WITH STORM TOTAL QPF AMOUNTS AVERAGING 1.0-1.5IN. THE COLD FRONT SWEEPS ACROSS THE REGION TUESDAY EVENING...USHERING IN A VERY COOL DRY AIRMASS. LOWS WEDNESDAY MORNING WILL LIKELY RANGE FROM THE UPPER 20S/LOW 30S OVER THE PIEDMONT TO THE UPPER 30S/LOW 40S ALONG THE COAST. HIGHS WEDNESDAY WILL BE CHILLY RANGING FROM 50-55 UNDER A MOSTLY SUNNY SKY.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... DRY CONDITIONS TO START OFF THE LONG TERM PERIOD WITH STRONG SFC HI PRES LOCKED IN PLACE OVR NEW ENGLAND AND RESULTING NE FLOW OVR THE MID ATLANTIC. AS WITH TUE NGT...POTENTIAL IS THERE WED NGT FOR FROST/FREEZE MAINLY OVR THE PIEDMONT WITH TEMPS FORECASTED TO FALL INTO THE MID 30S (LO 30S IS PSBL IN COLDEST SPOTS). WILL BE A BETTER CHANCE FOR FROST WED NGT THAN TUE NGT AS WINDS WILL BE LIGHTER. BLO NORMAL TEMPS CONTINUE INTO THU WITH HIGHS ONLY IN THE UPR 50S TO LWR 60S. THE SFC HI WILL REMAIN STRADDLED DOWN THE MID ATLANTIC CST THRU FRI LEADING TO PROLONGED NE FLOW AND BLO NORMAL TEMPS. MID-LEVEL ENERGY ARRIVES LATE FRI INTO SAT BRINGING THE NEXT CHANCE (30%) FOR RAIN. && .AVIATION /09Z MONDAY THROUGH FRIDAY/...
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HIGH PRESSURE REMAINS ANCHORED OFFSHORE THIS MORNING AS A STRONG COLD FRONT LOCATED OVER THE MIDWEST MAKES A SLOW PROGRESSION EWD. THE RESULT IS BREEZY SLY FLOW AT THE TAF SITES. WINDS HAVE DIMINISHED SLIGHTLY THIS MORNING...AVERAGING 10 KT. HIGH CLOUDS AOA 25K FT AGL ALSO STREAMING INTO THE REGION EARLY THIS MORNING. WINDS EXPECTED TO REMAIN SLY AT THE TAF SITES...SO DO NOT ANTICIPATE MVFR/IFR CIGS (STRATUS) THIS MORNING. HOWEVER...HAVE INCLUDED A SCT DECK AROUND 1500-2500 FT AGL TO ACCOUNT FOR UNCERTAINTY AND POSSIBLE STRATUS SPREADING OFF THE ADJACENT COASTAL WATERS. WILL CONTINUE TO MONITOR AND REMOVE FROM TAFS IF NECESSARY. FOR TODAY...DAYTIME MIXING WILL AGAIN RESULT IN STRONG SLY WINDS TODAY...GUSTING TO 25 TO 30 KT AT TIMES. SKIES WILL AVERAGE PARTLY SUNNY WITH FEW-SCT CLOUDS 3-5K FT AGL AND BKN-OVC SKIES AOA 25K FT AGL. MID LEVEL CLOUDS WILL INCREASE LATE TODAY AS THE FRONT APPROACHES FROM THE WEST. SHOWERS WILL BEGIN TO SPREAD OVER THE PIEDMONT INTO CNTRL VA TONIGHT. IFR CIGS POSSIBLE OVERNIGHT. OUTLOOK...BREEZY SOUTHERLY WINDS CONTINUE INTO TUESDAY (GUSTS OF 30-35 KT)AS THE FRONT APPROACHES FROM THE WEST. COLD FRONT WILL CROSS THE REGION TUES...ACCOMPANIED BY WIDESPREAD RAINFALL TUES-TUES NIGHT. THERE IS ALSO THE POTENTIAL FOR A STRONG LINE OF CONVECTION ON THE LEADING EDGE OF THE FRONT TUES AFTERNOON. HEAVY RAIN AND STRONG WIND GUSTS UP TO 50 KT ARE POSSIBLE. IFR VSBYS ALSO POSSIBLE IN HEAVY RAINFALL. BEHIND THE FRONT...WINDS WILL BACK TO THE NW AND REMAIN GUSTY. SOME GUSTS UP TO 40 KT POSSIBLE ALONG THE COAST. IMPROVING CONDITIONS WEDS THRU FRIDAY AS HIGH PRESSURE BUILDS INTO THE REGION.
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&& .MARINE...
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HIGH PRESSURE REMAINS ANCHORED OVER THE WRN ATLANTIC AS A STRONG COLD FRONT SLOWLY APPROACHES FROM THE WEST. BREEZY...BUT SUB SCA...SLY WINDS CONTINUE OVER THE WATERS...AVERAGING 10-15 KT. WAVES AVERAGE 1-2 FT WITH SEAS 2-3 FT. NRN COASTAL WATERS HAVE BUILT TO NEAR 4 FT 20 NM OUT...BUT ARE EXPECTED TO REMAIN BELOW 5 FT THRU THIS AFTERNOON DUE TO SLY FLOW. CONDITIONS WILL REMAIN SUB-SCA TODAY AS THE FRONT SLOWLY APPROACHES FROM THE WEST...WITH THE STRONGEST HEIGHT FALLS OCCURRING TUESDAY. HOWEVER...A FEW GUSTS APPROACHING 20 KT CANNOT BE RULED OUT. AS THE FLOW OVER THE WATERS BECOMES MORE SELY...SEAS WILL LIKELY BUILD TO 3-5 FT IN THE NRN WATERS...NORTH OF CAPE CHARLES LIGHT...BY LATE TODAY. LOW LEVEL GRADIENT WILL ALSO STRENGTHEN LATE TODAY-TONIGHT AS THE FRONT REACHES THE OH VALLEY. WHILE A STEEP LOW LEVEL INVERSION STILL EXISTS OVER THE WATERS...EXPECT PRESSURE FALLS AND GRADIENT WINDS TO PROVIDE BETTER MIXING OVER THE WATER. WHILE STILL MARGINAL...HAVE OPTED TO HOIST SCA HEADLINES TONIGHT FOR THE BAY. STRONGEST PRESSURE FALLS ARRIVE EARLY TUES...WITH LOW-END SCA CONDITIONS OVER THE BAY/SOUND/ERN VA RIVERS. SEAS ALSO EXPECTED TO BUILD TO 3-5 FT IN THE SRN WATERS (HIGHEST 20 NM OUT) TUES MORNING. SEAS WILL BUILD TO 5-8 FT TUES AFTERNOON. IN ADDITION...A LINE OF CONVECTION IS POSSIBLE ALONG THE LEADING EDGE OF THE FRONT TUES AFTERNOON. WITH WINDS A FEW THOUSAND FT OFF THE WATER REACHING 45-50 KT...CONVECTION WILL LIKELY BE ABLE TO MIX THESE HIGHER VELOCITY WINDS DOWN. WILL HANDLE THIS WITH SHORT FUSED PRODUCTS. THE MAIN IMPACT WILL BE BEHIND THE FRONT TUESDAY NIGHT AS A MUCH COLDER/DRIER AIRMASS SURGES INTO THE REGION. GALE CONDITIONS ARE EXPECTED OVER ALL WATERS...WITH NW GUSTS REACHING 35-40 KT. HAVE HELD OFF ON A GALE WATCH ATTM AS IT WILL STILL BE DURING THE 4TH PERIOD FORECAST. HIGH PRESSURE QUICKLY BUILDS BACK OVER THE WATERS EARLY WEDS MORNING...RESULTING IN IMPROVING CONDITIONS OVER THE BAY. FLOW VEERS AROUND TO THE NE WEDS...RESULTING IN PERSISTENT ONSHORE FLOW THRU THE END OF THE WEEK. THIS WILL RESULT IN ELEVATED SEAS THRU THE END OF THE WEEK.
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&& .AKQ WATCHES/WARNINGS/ADVISORIES...
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MD...NONE. NC...NONE. VA...NONE. MARINE...SMALL CRAFT ADVISORY FROM 4 AM TO 6 PM EDT TUESDAY FOR ANZ633- 635>638. SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 6 PM EDT TUESDAY FOR ANZ630>632-634-650-652-654. SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 6 PM EDT TUESDAY FOR ANZ656-658.
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&& $$ SYNOPSIS...AJZ NEAR TERM...AJZ SHORT TERM...AJZ LONG TERM...MAS AVIATION...SAM MARINE...SAM

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