Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 171958 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 358 PM EDT FRI OCT 17 2014 .SYNOPSIS...
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HIGH PRESSURE MOVES OFF THE SOUTHEAST COAST TONIGHT AHEAD OF A DRY COLD FRONT...WHICH CROSSES THE MID ATLANTIC LATER SATURDAY. COOL CANADIAN HIGH PRESSURE BUILDS IN FROM THE NORTHWEST SATURDAY NIGHT AND SUNDAY.
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&& .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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MID-AFTERNOON WX ANALYSIS FEATURES DOUBLE BARRELED LOW PRESSURE SYSTEM IN PLACE FROM SOUTHERN QUEBEC BACK INTO THE UPPER GREAT LAKES. THIS STRUCTURE IS A COMBINATION OF THE EAST COAST TROUGH OF THE PREVIOUS FEW DAYS AND A COMPACT UPPER LOW SLIPPING EAST ACROSS THE UPPER MIDWEST FROM THE NORTHERN PLAINS/CANADIAN PRAIRIES. THE SFC COLD FRONT ASSOCIATED WITH THE LATTER FEATURE EXTENDED SOUTH INTO THE OHIO VALLEY AND THE TEXARKANA AT 20Z. MEANWHILE CLOSER TO HOME, SFC HIGH PRESSURE REMAINS IN PLACE OVER THE DEEP SOUTH, WITH THE SFC RIDGE AXIS ALONG THE EASTERN SEABOARD. HIGH PRESSURE WILL SLIDE OFFSHORE TONIGHT AS LEADING SHORTWAVE PUSHES ACROSS THE GREAT LAKES. ONGOING LIGHT WAA RESULTS IN LOW TEMPERATURES ON THE WARM SIDE OF SEASONAL AVERAGES. LOOK FOR OVERNIGHT LOWS IN THE LOW/MID 50S.
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&& .SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/...
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THE FIRST SHORTWAVE TROUGH PIVOTS ACROSS THE EASTERN GREAT LAKES INTO NORTHERN NEW ENGLAND ON SATURDAY...WITH THE ASSOCIATED COLD FRONT APPROACHING FROM THE NW AND CROSSING THE AREA SATURDAY. MEANWHILE, A SECOND STRONG DISTURBANCE CURRENTLY PUSHING ACROSS THE CANADIAN PRAIRIES WILL DROP ACROSS THE OHIO/TN VLY TOMORROW INTO TOMORROW EVENING. CONTINUED MILD WITH DOWNSLOPE W-NW FLOW OUT AHEAD OF THE COOL FRONT TOMORROW, WITH HIGHS AVERAGING IN THE LOW/MID 70S...ALTHOUGH FAR NW PORTIONS OF OUR AREA COULD REMAIN IN THE UPPER 60S AS LOW- LEVEL THICKNESSES FALL THROUGH THE DAY. CLEAR TO BEGIN THE DAY, WITH SOME INCREASING CLOUDS WITH BY MIDDAY, ESPECIALLY WEST. FORECAST WILL AVERAGE OUT MOSTLY SUNNY FOR MOST EXCEPT FOR FAR NW ZONES. SECOND DISTURBANCE WILL SHUNT TROUGH AXIS ACROSS THE MID ATLANTIC SATURDAY NIGHT, PUSHING OFFSHORE SUNDAY MORNING AS SHORTWAVE RIDGING TRANSLATES EAST FROM THE PLAINS LATER SUNDAY AND MONDAY. ISENTROPIC FIELDS REVEAL MINIMAL VERTICAL ASCENT DURING THIS PERIOD...AND THE AIRMASS WILL REMAIN DRY AS CAA SURGE ENSUES. EXPECT A PERIOD OF MOSTLY CLOUDY CONDITIONS NORTH SATURDAY NIGHT (PARTLY CLOUDY CENTRAL/SOUTH). DO HAVE THE POTENTIAL FOR A FEW SPRINKLES ACROSS FAR NRN PORTIONS. HOWEVER, CHCS OF MEASURING ARE MINIMAL, SO A SILENT POP HAS BEEN MAINTAINED. EITHER WAY, CLOUDS LOOK TO SCOUR OUT QUICKLY LATE SAT NIGHT/SUNDAY MORNING AS AN EVEN DRIER AIRMASS ARRIVES WITH CANADIAN HIGH PRESSURE BUILDING IN FROM THE NW. EARLY MORNING LOW TEMPERATURES SHOULD DROP INTO THE LOW 40S OVER THE PIEDMONT SUNDAY MORNING...WITH MID/UPPER 40S OVER MOST OF THE AREA...AND LOW/MID 50S FOR SE COASTAL LOCATIONS. BEHIND THE DEPARTING UPPER TROUGH, COOL NW FLOW ALOFT/HIGH PRESSURE BUILDING IN FROM THE WEST WILL BRING A COOLER DAY ON SUNDAY WITH HIGHS IN THE LOW TO MID 60S. BY MONDAY, THE SURFACE HIGH SHIFTS OFFSHORE ALLOWING SFC WINDS TO SHIFT AROUND TO THE SOUTH. RESULTANT WEAK WAA AND MODEST HEIGHT RISES YIELD SLIGHTLY MILDER TEMPERATURES MONDAY BACK INTO THE LOW TO MID 60S.
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&& .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
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AN UPPER TROUGH IS EXPECTED TO DIG THROUGH THE OHIO VALLEY MONDAY NIGHT AND TUESDAY AS LOW PRESSURE DEVELOPS IN VICINITY OF THE GULF STREAM. THE TREND AMONGST 17/12Z NUMERICAL GUIDANCE IS FOR THE TROUGH TO CLOSE OFF AND SLOWLY TRAVERSE THE MID-ATLANTIC REGION WEDNESDAY INTO THURSDAY WITH SURFACE LOW PRESSURE LIFTING NNE OFF THE COAST. POPS HAVE ACCORDINGLY BEEN ADJUSTED TO REFLECT A 25-40% CHC OF SHOWERS TUES/WED...TAPERING TO 20% THURSDAY AS HIGHEST CHANCES WILL BE OVER THE EASTERN SHORE/COASTAL WATERS. THE PRESENCE OF THE UPPER SYSTEM AND LOW-LEVEL NORTHERLY FLOW (BY WED/THU) SHOULD RESULT IN CONSIDERABLE CLOUD COVER AND COOLER TEMPERATURES. HIGHS TUESDAY ARE FORECAST TO RANGE FROM THE LOW 60S NW...TO AROUND 70 SE...FOLLOWED BY MID 50S NW TO LOW/MID 60S SE WEDNESDAY AND THURSDAY. OVERNIGHT LOWS SHOULD AVERAGE IN THE MID 40S TO LOW 50S. THE UPPER LOW QUICKLY LIFTS INTO NEW ENGLAND NEXT FRIDAY FOR DRY WX. FRIDAY`S HIGHS ARE EXPECTED TO RETURN TO THE 60S ALL AREAS.
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&& .AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
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HIGH PRESSURE CENTERED OVER THE GULF COAST STATES HAS BUILD NORTHWARD INTO THE MID ATLANTIC STATES AND WITH LOW MOISTURE IN PLACE...IS PROVIDING MAINLY CLEAR SKY AND VFR CONDITIONS. THIS HIGH EDGE OFF THE COAST TONIGHT AS A COLD FRONT APPROACHES FROM THE WEST. THIS WILL SERVE TO KEEP THE SW FLOW A LITTLE STRONGER OVERNIGHT AND ENOUGH TO KEEP FOG FROM DEVELOPING SO EXPECT VFR CONDITIONS TONIGHT. ON SAT MORNING...BETWEEN 9Z AND 15Z...THE COLD FRONT WILL CLEAR THE AREA...BUT WITH LITTLE MOISTURE...NOT ANTICIPATING MUCH IN THE WAY OF CLOUDS AND NO RAIN. THE WINDS WILL SHIFT TO THE NW AND WILL INCREASE TO 10 TO 15 KT. BY MID TO LATE AFTERNOON...THE COOLING ALOFT WILL HELP TO GENERATE MORE CU AND A BROKEN DECK IS POSSIBLE...BUT IT WILL REMAIN ABOVE 3K FT. THE CLOUDS WILL LINGER INTO THE OVERNIGHT HOURS BEFORE CLEARING BEFORE SUNRISE SUNDAY DRY AND VFR CONDITIONS PREVAIL SUNDAY THROUGH MONDAY NIGHT WITH THE WINDS RELAXING SUNDAY AFTERNOON AS HIGH PRESSURE SETTLES OVER THE AREA. THE NEXT CHANCE FOR MVFR CONDITIONS COMES ON TUESDAY AS A COLD FRONT AND STRONG LOW PRESSURE SYSTEM MOVE INTO THE REGION.
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&& .MARINE...
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A COLD FRONT APPROACHES THE WATERS FROM THE WEST LATE TONIGHT. IN ADVANCE OF THE FRONT...SW WINDS WILL REMAIN 5-15 KT THRU SUNSET. WINDS SHOULD NOTICEABLY INCREASE ON THE BAY/SOUND/OCEAN BY THIS EVENING...REACHING SCA CRITERIA TONIGHT. THIS IN RESPONSE TO SOME STRONG WINDS JUST OFF THE SURFACE (ASSOCIATED WITH A PRE-FRONTAL TROUGH) BEING ABLE TO MIX DOWN AS THE AIR TEMP COOLS AFTER SUNSET. WINDS ARE EXPECTED TO BE 15-25 KT (WITH SOME GUSTS TO 30 KT POSSIBLE ON THE NORTHERN COASTAL WATERS). WINDS REMAIN BELOW 15 KT ON THE RIVERS. WAVES MAY BRIEFLY REACH 4 FT ON THE BAY. SEAS WILL CONTINUE TO BUILD TO 5-6 FT ON THE OCEAN. A COLD FRONT CROSSES THE WATERS SAT WITH FLOW BECOMING NW LATE SAT INTO SAT NIGHT AS COOL CANADIAN HIGH PRESSURE DIVES OVER THE GREAT LAKES REGION. GRADIENT WINDS REALLY RAMP UP SAT NIGHT WITH SCA CONDITIONS EXPECTED ALL WATERS SAT NIGHT THRU SUN MORNING. NW WINDS OF 20-25 KT WITH GUSTS UP TO 30 KT EXPECTED. WAVES INCREASE TO 3-4 FT AS SEAS REMAIN ELEVATED AT 5-7 FT. HAVE HELD OFF ON SCA HEADLINES FOR THE BAY/RIVERS/SOUND AS THERE WILL BE AT LEAST A 12-HR WINDOW OF SUB-SCA WINDS DURING SAT...AND TO ALLOW CURRENT HEADLINES TO EXPIRE...BUT CONFIDENCE IS HIGH FOR SCA CONDITIONS. THE HIGH CENTER BUILDS OVER THE WATERS SUN NIGHT/MON...ALLOWING SUB-SCA CONDITIONS TO RETURN. WHILE THERE REMAINS SOME MODEL UNCERTAINTY...THE NEXT COLD FRONT IS EXPECTED TO CROSS THE WATERS LATE TUES...ACCOMPANIED BY CAA AND MORE SCA CONDITIONS. SYSTEM IS EXPECTED TO STALL OFF THE COAST THRU THE END OF THE WEEK...WHICH MAY RESULT IN A PROLONGED PERIOD OF SCA CONDITIONS.
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&& .AKQ WATCHES/WARNINGS/ADVISORIES... MD...NONE. NC...NONE. VA...NONE. MARINE...SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 4 AM EDT SATURDAY FOR ANZ630>634. SMALL CRAFT ADVISORY UNTIL 6 AM EDT SUNDAY FOR ANZ650-652-654- 656-658. && $$ SYNOPSIS...MAM NEAR TERM...MAM SHORT TERM...AJZ/MAM LONG TERM...AJZ AVIATION...ESS MARINE...SAM

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