Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 130900 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 500 AM EDT SUN APR 13 2014 .SYNOPSIS... HIGH PRESSURE REMAINS OFF THE MID ATLANTIC COAST THROUGH MONDAY. 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. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... THE CURRENT WV IMAGERY SHOWS A MID/UPPER RIDGE OVER THE WESTERN ATLANTIC...WITH A TROUGH LIFTING NE THROUGH THE CENTRAL PLAINS. AT THE SURFACE...HIGH PRESSURE IS CENTERED OFF THE MID ATLANTIC COAST...WITH A WAVY FRONTAL BOUNDARY FROM THE SOUTHERN HIGH PLAINS TO THE GREAT LAKES. THE UPPER RIDGE WILL PREVAIL TODAY...WITH SURFACE HIGH PRESSURE REMAINING ANCHORED OFF THE COAST. THIS WILL PRODUCE A BREEZY WARM DAY...WITH HIGHS RANGING FROM THE UPPER 70S TO LOW 80S (LOCALLY COOLER ALONG THE ATLANTIC COAST)..ALONG WITH A SOUTHERLY WIND OF 10-15 MPH (GUSTS TO 20-25 MPH). && .SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY/... THE MID/UPPER RIDGE OVER THE WESTERN ATLANTIC REMAINS THE DOMINANT FEATURE LOCALLY TONIGHT INTO MONDAY AS THE CENTRAL PLAINS TROUGH LIFTS NE THROUGH THE GREAT LAKES AND REMAINS WELL NW THE CWA. EXPECT A MOSTLY CLEAR SKY TONIGHT...FOLLOWED BY INCREASING HIGH CLOUDS MONDAY AS THE RIDGE SLOWLY NUDGES FARTHER OFFSHORE. FORECAST SOUNDINGS INDICATE MOISTENING BELOW 950MB LATER TONIGHT...SO THERE COULD BE SOME PATCHY STRATUS (AS OPPOSED TO FOG DUE TO AN 8-10KT S WIND) LATE TONIGHT/EARLY MONDAY. LOWS MONDAY MORNING WILL BE MILD RANGING FROM THE UPPER 50S TO AROUND 60. HEIGHT FALLS AND INCREASING CLOUDS WILL RESULT IN HIGHS MONDAY BEING A FEW DEGREES LOWER THAN SUNDAY...WITH READINGS IN THE MID/UPPER 70S (LOCALLY COOLER ALONG THE ATLANTIC COAST). A SECONDARY SHORTWAVE TROUGH DIGS ACROSS THE PLAINS MONDAY AND INTO THE MISSISSIPPI VALLEY MONDAY NIGHT. THIS RESULTS IN A SHARP AMPLIFICATION OF THE LONGWAVE PATTERN MONDAY NIGHT INTO TUESDAY. A STRONG COLD FRONT WILL ACCOMPANY THE PATTERN AMPLIFICATION AND SWEEP ACROSS THE OHIO VALLEY MONDAY NIGHT AND TOWARD THE EAST COAST TUESDAY. THE PROBABILITY OF RAIN WILL INCREASE SHARPLY LATE MONDAY NIGHT...AND ESPECIALLY INTO TUESDAY AS THE FRONTAL SYSTEM MOVES INTO THE REGION. THERE WILL BE A CONSIDERABLE AMOUNT OF DEEP LAYER BULK SHEAR...ALONG WITH STRONG SYNOPTIC SCALE FORCING. INSTABILITY WILL BE MORE LIMITED DUE TO A DEEP MOIST THERMAL PROFILE. HOWEVER...SREF PROBS DO INDICATE A HIGH LIKELIHOOD OF 2M DEWPOINTS GREATER THAN 60F...ALONG WITH STRONG MOISTURE ADVECTION ASSOCIATED WITH A +3-4 ST DEV LOW-LEVEL JET. GIVEN THIS...THERE IS SUPPORT FOR A FORCED LINE OF STRONG CONVECTION AT THE LEADING EDGE OF THE FRONTAL RAIN BAND. MODERATE TO BRIEF HEAVY RAIN IS EXPECTED. HOWEVER...THE DURATION SHOULD LIMIT STORM TOTAL QPF AMOUNTS TO ~1.0IN. MONDAY NIGHT WILL BE VERY MILD FOR APRIL WITH LOWS IN THE LOW 60S. HIGHS TUESDAY WILL BE LIMITED BY CLOUDS AND SHRA...BUT STILL RANGE FROM THE MID/UPPER 60S W...TO THE UPPER 60S/LOW 70S E. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
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13/00Z NUMERICAL GUIDANCE HAS COME INTO BETTER AGREEMENT WITH RESPECT TO A STRONG COLD FRONT PUSHING OFFSHORE TUESDAY EVENING...FOLLOWED BY CANADIAN HIGH PRESSURE BUILDING ACROSS THE MID ATLANTIC AND NORTHEAST LATE TUESDAY NIGHT INTO WEDNESDAY. POPS WERE LOWERED LATE TUESDAY NIGHT INTO WEDNESDAY TO ACCOUNT FOR THIS. MSLP PER GEFS IS PROGGED TO REACH 1040MB (+3-4 ST DEV) OVER ME/NB BY 12Z THURSDAY...WITH SEA-LEVEL PRESSURE OF +2-3 ST DEV LOCALLY. MEANWHILE...A TROUGH OF LOW PRESSURE IS EXPECTED TO REMAIN OFFSHORE. THIS WILL RESULT IN A PROLONGED PERIOD OF ONSHORE FLOW. THE SKY SHOULD INITIALLY CLEAR QUICKLY LATE TUESDAY NIGHT INTO WEDNESDAY...BEFORE BECOMING MORE PARTLY/MOSTLY CLOUDY (ESPECIALLY SE) DUE TO PERSISTENT ONSHORE FLOW. AS FOR TEMPS...READINGS WILL AVG BLO NORMAL FOR THE PERIOD...WITH HIGHS IN THE 50S AND 60S. THE LATEST GUIDANCE SUGGESTS TEMPS TUE NIGHT FALL TO 28-32F OVER THE PIEDMONT...WITH 30-34F WED NIGHT. THE LATEST FORECAST IS NOT THAT COLD...BUT HAS BEEN TRENDED IN THAT DIRECTION. THIS WILL BRING THE POTENTIAL FOR FROST OR FREEZE. OF NOTE...THE FROST/FREEZE PROGRAM DOES NOT BEGIN FOR THE FAR NW COUNTIES (LOUISA/FLUVANNA/GOOCHLAND/CUMBERLAND/PRINCE EDWARD) UNTIL APR 25...WITH THE BORDERING COUNTIES BEGINNING APR 15.
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&& .AVIATION /09Z SUNDAY THROUGH THURSDAY/... HIGH PRESSURE HAS LOCATED OFF THE MID-ATLANTIC COAST AS A WARM FRONT LIFTS NWD OVER THE AREA THIS MORNING. THE RESULT IS SLY FLOW AOB 10 KT AT THE TAF SITES. THE EXCEPTION IS KSBY WITH SELY WINDS JUST IN ADVANCE OF THE BOUNDARY. CANNOT RULE OUT MVFR STRATUS/FOG THIS MORNING AT KSBY DUE TO SE FLOW...BUT LATEST IR SATELLITE NOT DETECTING LOW CLOUDS OVER THE OCEAN...EVEN THOUGH OXB IS REPORTING A SCT DECK AT 1100 FT AGL. WILL CONTINUE TO MONITOR...BUT CONFIDENCE IS NOT HIGH ENOUGH ATTM TO INCLUDE IN TAF. WILL MAINTAIN MVFR VSBYS 10-13Z. FOR TODAY...SLY WINDS WILL INCREASE LATE MORNING INTO THE AFTERNOON AS THE GRADIENT STRENGTHENS BTWN HIGH PRESSURE OVER THE WRN ATLANTIC AND LOW PRESSURE OVER THE MIDWEST. EXPECT GUSTS UP TO 20-25 KT. EXPECT PERIODS OF HIGH CLOUDS AOA 25K FT AGL THIS MORNING WITH FEW-SCT CLOUDS 4-6K FT AGL THIS AFTERNOON. BREEZY SLY WINDS WILL CONTINUE THROUGH TUES IN ADVANCE OF A STRONG COLD FRONT SET TO IMPACT THE REGION MON NIGHT-TUES NIGHT. WIDESPREAD RAINFALL IS EXPECTED...WITH IFR VSBYS POSSIBLE IN HEAVIER PRECIP. WIND GUSTS OF 30-35 KT ARE ALSO POSSIBLE. HIGH PRESSURE BUILDS INTO THE REGION WEDS AND THURSDAY. && .MARINE... HIGH PRESSURE HAS LOCATED OFF THE MID-ATLANTIC COAST THIS MORNING AS A WARM FRONT LIFTS OVER THE WATERS. THE RESULT IS SLY FLOW THIS MORNING GENERALLY AOB 10 KT WITH WAVES 1 FT AND SEAS 1-2 FT. A STRONG COLD FRONT OVER THE MIDWEST THIS MORNING WILL SLOWLY APPROACH THE WATERS THRU TUES AS HIGH PRESSURE REMAINS ANCHORED OVER THE WRN ATLANTIC. THE RESULTANT PRESSURE GRADIENT WILL RESULT IN BREEZY SLY WINDS BEGINNING THIS AFTERNOON AND CONTINUING THRU MONDAY. STEEP LOW LEVEL INVERSION WILL LIMIT MIXING THIS AFTERNOON AS WARM AIR ADVECTS OVER COLD WATERS. PRESSURE FALLS WILL ALSO BE LIMITED TODAY AS THE FRONT REMAINS WELL TO THE WEST. EXPECT SUSTAINED SPEEDS AROUND 15 KT IN THE BAY AND 20 KT IN THE COASTAL WATERS WITH GUSTS APPROACHING 20 KT AND 25 KT RESPECTIVELY. USED A LOWER GUST FACTOR DUE TO SLY WINDS. GFS STILL TOO STRONG WITH SLY WINDS OVER THE COASTAL WATERS...AS WAVEWATCH ATTEMPTS TO BUILD SEAS TO 4-6 FT IN THE NRN WATERS. SEAS WILL LIKELY REMAIN BELOW 5 FT AS SLY WINDS WILL BE SLOW TO BUILD SEAS. THUS...NO HEADLINES PLANNED FOR TODAY-TONIGHT. MORE OF THE SAME MON AS THE FRONT REACHES THE OH VALLEY LATE IN THE DAY. PERSISTENT SLY WINDS WILL BEGIN TO BUILD THE NRN WATERS TOWARD 5 FT. BY MON NIGHT INTO TUES...PRESSURE FALLS WILL LIKELY BEGIN TO MIX THE STRONGER WINDS ALOFT TO THE WATER. NAM V COMPONENT (N-S) REACHES +4 STD DEV OVER THE WATERS. SEAS WILL ALSO BUILD TO 4-6 FT. THE FRONT IS FORECAST TO CROSS THE WATERS TUES AFTERNOON-TUES EVENING. STRONG CAA AND LOW LEVEL WINDS BEHIND THE FRONT WILL RESULT IN SOLID SCA CONDITIONS OR POSSIBLY LOW END GALES. STRONG HIGH PRESSURE WILL BUILD OVER THE WATERS WED-THURS...BUT PROLONGED NE FLOW WILL LIKELY KEEP SEAS ELEVATED THROUGH THE END OF THE WEEK. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...NONE. NC...NONE. VA...NONE. MARINE...NONE. && $$ SYNOPSIS...AJZ/MAM NEAR TERM...AJZ SHORT TERM...AJZ/MAM LONG TERM...AJZ/MAS AVIATION...SAM MARINE...SAM

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