Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 290804 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 404 AM EDT SUN MAR 29 2015 .SYNOPSIS...
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HIGH PRESSURE SETTLES OVER THE REGION TODAY AND MOVES OFFSHORE THIS EVENING. A WEAK COLD FRONT APPROACHES FROM THE NORTHWEST THIS EVENING AND MOVES ACROSS THE AREA LATE TONIGHT THROUGH EARLY MONDAY MORNING. HIGH PRESSURE RETURNS MONDAY AFTERNOON INTO MONDAY NIGHT. LOW PRESSURE TRACKS ACROSS THE NORTHERN MID ATLANTIC TUESDAY WITH THE ASSOCIATED COLD FRONT DROPPING THROUGH THE REGION TUESDAY NIGHT.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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THE LATEST SURFACE ANALYSIS SHOWS 1030MB HIGH PRESSURE CENTERED OVER THE UPPER OHIO VALLEY. THIS HIGH IS SLOWLY BUILDING INTO THE MID ATLANTIC WITH MANY LOCATIONS OVER THE PIEDMONT AND INTERIOR COASTAL PLAIN NOW DECOUPLING EVIDENCED BY CALM CONDITIONS. MEANWHILE...A GUSTY NW WIND PERSISTS ALONG THE COAST. TEMPERATURES OVER THE PIEDMONT AND INTERIOR COASTAL PLAIN HAVE GENERALLY DROPPED INTO THE LOW/MID 20S AS OF 330AM WITH LKU SHOWING A TEMPERATURE OF 18 AT 315AM. FARTHER E...TEMPERATURES REMAIN IN THE UPPER 20S TO LOW 30S...ALTHOUGH WIND CHILL VALUES ARE IN THE LOW 20S. SEE THE CLIMO SECTION BELOW FOR RECORD LOWS FOR THIS MORNING. HIGH PRESSURE WILL BUILD ACROSS THE SOUTHEAST STATES TODAY...WHICH WILL RESULT IN SUNNY AND DRY CONDITIONS LOCALLY ALONG WITH A LIGHT WIND. MIXING WILL BE LIMITED WITH HIGH PRESSURE OVERHEAD...SO HIGHS WILL ONLY REACH THE LOW/MID 40S ALONG THE COAST...TO LOW 50S OVER INTERIOR VA/NE NC DESPITE FULL SUN. THESE VALUES WILL AVERAGE ABOUT -1.5 ST DEV BELOW THE SEASONAL MEAN.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY/...
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HIGH PRESSURE SHIFTS OFFSHORE TONIGHT AS A MID-LEVEL TROUGH TRACKS ACROSS THE GREAT LAKES. AN ASSOCIATED MID-LEVEL COLD FRONT THEN MOVES ACROSS THE MID ATLANTIC LATE TONIGHT THROUGH MIDDAY MONDAY. NUMERICAL MODELS SHOW A DECENT BAND OF UVM SLIDING NW-SE ACROSS THE LOCAL AREA BETWEEN ABOUT 09-18Z. HOWEVER...MOISTURE REMAIN VERY LIMITED BELOW 850MB. GIVEN THIS HAVE TRENDED POPS UPWARD INTO THE HIGH CHC CATEGORY (40-50%) FOR WHAT SHOULD AMOUNT TO A LIGHT QPF EVENT (~0.10IN OR LESS). TEMPERATURES SHOULD DROP QUICKLY THIS EVENING UNDER A CLEAR SKY. OVERNIGHT LOWS SHOULD BE COLDEST E (LOW 30S) WHERE CLEAR CONDITIONS WILL PERSIST THE LONGEST. FARTHER W...LOWS SHOULD BE IN THE MID/UPPER 30S...BUT SURFACE WET-BULBS WILL BE IN THE LOW 30S SO IT IS POSSIBLE THAT THE ONSET OF PCPN COULD INCLUDE A MIX OF -RA/IP. THE SURFACE PORTION OF THE COLD FRONT IS MAINLY A WIND SHIFT...SO HIGHS MONDAY WILL BE WARMER AVERAGING FROM THE UPPER 50S/LOW 60S ALONG THE COAST...TO THE MID 60S INLAND WITH DOWNSLOPE WESTERLY FLOW IN THE WAKE OF THE BOUNDARY. A FAST MOVING LOW PRESSURE SYSTEM DRIVEN BY ZONAL FLOW ALOFT TRACKS ACROSS THE NRN MID ATLANTIC TUESDAY AFTERNOON. EXPECT MOSTLY SUNNY CONDITIONS TO BEGIN THE DAY WITH INCREASING CLOUDS ACROSS THE N BY AFTERNOON. A RIBBON OF 20-25% POPS (FOR -SHRA) HAS BEEN INCLUDED FOR THE NRN TIER COUNTIES AND THIS IS MAINLY TO ACCOUNT FOR UNCERTAINTY OF THE LOW TRACK. IT WILL BE DIFFICULT TO GET ANY PCPN S OF THE LOW TRACK WITH DEEP LAYERED WSW FLOW. LOW-LEVEL THICKNESS VALUES SUPPORT HIGHS APPROACHING 70F ON TUESDAY OVER INTERIOR VA/NE NC. THIS IS CERTAINLY POSSIBLE WITH LOW PRESSURE TRACKING N OF THE REGION RESULTING IN DEEP LAYERED WSW FLOW. FORECAST HIGHS HAVE BEEN INCREASED INTO THE UPPER 60S OVER THE AFOREMENTIONED AREAS...WITH LOW 60S OVER THE ERN SHORE...AND LOCALLY COOLER VALUES ALONG THE IMMEDIATE ATLANTIC COAST. THIS WILL BE AFTER MORNING LOWS IN THE UPPER 30S TO LOW 40S.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... BETTER AGREEMENT IN MEDIUM RANGE GUIDANCE WITH RESPECT TO HANDLING SPLIT FLOW COMPARED TO 24 HRS AGO. TO BEGIN THE EXTENDED...GOOD MODEL CONSENSUS NOW WITH A NRN STREAM WAVE DROPPING INTO THE NRN MID- ATLANTIC REGION LATE TUES NIGHT. ASSOCIATED SFC LOW PROGGED TO TRACK ACROSS NRN VA/MD TUES NIGHT WITH A WEAK COLD FRONT SWEEPING ACROSS THE REGION EARLY WEDS MORNING. BEST MOISTURE/LIFT WILL BE NORTH OF THE LOCAL AREA...BUT WILL INTRODUCE SLIGHT CHANCE-LOW END CHANCE POPS ACROSS THE NE ZONES LATE TUES NIGHT CLOSEST TO BEST MOISTURE/LIFT. SFC LOW AND COLD FRONT PUSH WELL OFFSHORE WEDS AS SFC HIGH PRESSURE CENTERS OVER THE REGION. MODEST CAA AND MOSTLY SUNNY SKIES WILL RESULT IN TEMPS IN THE LOW-MID 60S INLAND AND MID-UPPER 50S ERN SHORE AND COASTAL AREAS. HIGH PRESSURE PUSHES OFFSHORE WEDS NIGHT-THURS AS A SRN STREAM WAVE LIFTS FROM THE SRN PLAINS INTO THE TN VALLEY. MOISTURE RETURN EXPECTED THANKS TO INCREASING S-SE FLOW. 28/12Z ECMWF QUICKER WITH BRINGING PRECIP INTO THE REGION THURS AFTERNOON. HAVE DROPPED POPS THURS AFTERNOON...BUT KEPT SLIGHT CHANCE POPS ACROSS THE PIEDMONT. SSW FLOW WILL HELP MODERATE TEMPS INTO THE UPPER 60S TO AROUND 70 INLAND TO LOW-MID 60S COASTAL AREAS THURS. EXPECT CLOUDS TO INCREASE THURS AFTERNOON. THEREAFTER...CHANCE FOR PRECIP RAMP UP THURS NIGHT-FRI AS THE SRN STREAM WAVE LIFTS OVER THE REGION. NRN STREAM WAVE OVER THE UPPER MIDWEST ALSO PROGGED TO FLATTEN AND TRACK ACROSS THE GREAT LAKES REGION LATE THURS-THURS NIGHT. ASSOCIATED OCCLUDED SFC LOW LOCATES OVER SERN CANADA THURS NIGHT-FRI MORNING...WITH AN ATTENDANT COLD FRONT CROSSING THE REGION DURING THE FRI-SAT TIMEFRAME. SPATIAL AND TIMING DIFFERENCES EXIST...BUT WILL CARRY CHANCE POPS THRU SAT MORNING. SLIGHT WARMER FRI WITH HIGHS IN THE LOW-MID 70S INLAND AND LOW-MID 60S COASTAL AREAS. && .AVIATION /08Z SUNDAY THROUGH THURSDAY/... VFR CONDITIONS EXPECTED THROUGH THE 06Z TAF PERIOD. DEEP UPPER TROUGH WILL SLIDE OFF THE COAST THIS MORNING WITH HIGH PRESSURE BUILDING OVER THE REGION LATER TODAY. NW WINDS WILL DIMINISH SLIGHTLY EARLY THIS MORNING WITH SOME INCREASE IN THE WINDS ONCE AGAIN DURING THE DAY TODAY. OUTLOOK...THE AFOREMENTIONED HIGH WILL MOVE TO THE SOUTH TONIGHT AS A WEAK COLD FRONT CROSSES THE AREA EARLY MONDAY. THERE WILL BE SLGT TO LOW CHC FOR SHOWERS EARLY MONDAY. HIGH PRESSURE BUILDS BACK INTO THE AREA EARLY NEXT WEEK. A CHANCE FOR SHOWERS RETURNS THURSDAY. && .MARINE...
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LATEST SFC ANALYSIS REVEALS BROAD HI PRES CENTERED OVER THE OH VALLEY. STRONG WINDS CONTINUE THIS MORNG WITH PRES RISES AND CAA OVER THE LOCAL AREA. SCA HEADLINES CONTINUE AS PLANNED...ENDING LATER THIS MORNG OVER THE BAY...THEN OVER THE BAY/SOUND...AND FINALLY OVER CSTL WTRS MIDDAY AS SEAS SUBSIDE TO BLO 5FT. IMPROVING MARINE CONDS EXPECTED THIS AFTN AS THE HI CENTERS OVER THE CAROLINAS. THE NEXT COLD FRONT APPROACHES FROM THE WEST TONIGHT... CROSSING THE WATERS LATE MON-EARLY MON NIGHT. PREFRONTAL SLY SURGE EXPECTED LATE TONIGHT...WITH SPEEDS INCREASING TO 15 KT IN THE BAY AND 20 KT IN THE COASTAL WATERS. MODELS INDICATE SCA CONDITIONS...BUT BASED ON WAA AND COLD WATER...EXPECT A SHARP LOW LEVEL INVERSION TO PREVENT STRONGEST WINDS FROM MIXING TO THE WATER. HAVE CAPPED SPEEDS BELOW SCA ATTM AND WILL CONTINUE TO MONITOR AS CONDS WILL BE CLOSE TO SCA THRESHOLDS. SLY FETCH MAY PUSH SEAS TO 5 FT IN THE NRN COASTAL WATERS MON MORNING. SWLY FLOW RETURNS MON NIGHT-TUES. LOW PRESSURE TRACKS ACROSS THE MID-ATLANTIC REGION LATE TUES WITH ANOTHER FRONT CROSSING THE WATER EARLY WEDS NIGHT. WINDS STAY AOB 15 KT. HIGH PRESSURE RETURNS WEDS-THURS.
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&& .CLIMATE... RECORD LOW TEMPERATURES FOR SUNDAY 3/29: RIC...22/1923 ORF...25/1982 SBY...18/1923 ECG...24/1982 && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...NONE. NC...NONE. VA...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 7 AM EDT THIS MORNING FOR ANZ635>638. SMALL CRAFT ADVISORY UNTIL 10 AM EDT THIS MORNING FOR ANZ630>634. SMALL CRAFT ADVISORY UNTIL 1 PM EDT THIS AFTERNOON FOR ANZ650- 652-654-656-658. && $$ SYNOPSIS...AJZ/JAO NEAR TERM...AJZ SHORT TERM...AJZ/JAO LONG TERM...SAM AVIATION...MAS/DAP/LSA MARINE...MAS CLIMATE...AKQ

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