Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 201021 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 621 AM EDT SAT SEP 20 2014 .SYNOPSIS... DEVELOPING LOW PRESSURE OFF FLORIDA WILL LIFT NORTH THROUGH THE WEEKEND...PASSING JUST OFF THE CAROLINA COASTS. THIS LOW PRESSURE WILL REMAIN JUST FAR ENOUGH OFFSHORE SUCH THAT IMPACTS WILL BE LIMITED...BUT SHOWERS AND SOME INCREASED WIND IS LIKELY...ESPECIALLY ALONG THE COAST. A COLD FRONT WILL CROSS THE AREA MONDAY...WITH COOL HIGH PRESSURE FOLLOWING BEHIND IT THROUGH THE MIDDLE OF NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 630 AM SATURDAY...NO CHANGES TO THE FORECAST WITH THE LATEST UPDATE. PREVIOUS DISCUSSION FOLLOWS: MODELS IN DECENT AGREEMENT THAT CYCLOGENESIS WILL OCCUR ALONG A STALLED FRONT OVER THE BAHAMAS...WITH THE DEEPENING LOW MOVING NORTHEAST AND OFFSHORE OF THE EAST COAST TODAY AND TONIGHT. WHILE DETAILS DIFFER...A CONSENSUS OF GUIDANCE HAS THE LOW CENTERED SOUTHEAST OF BEAUFORT NC BY DAYBREAK ON SUNDAY. THE EASTERN CAROLINAS WILL BE ON THE BACKSIDE OF THE LOW WITH A MOIST NORTHEAST FLOW EARLY IN THE PERIOD BECOMING MORE NORTHERLY AFTER MIDNIGHT AS THE LOW MOVES OFFSHORE. THE MAIN FORECAST CHALLENGE WILL BE EXTENT AND AMOUNT OF PRECIPITATION. BASED ON CURRENT TRACK AND MODEL SOUNDINGS WILL INTRODUCE HIGH CHANCE TO LIKELY POPS ALONG THE COAST...WITH CHANCES INCREASING THROUGH THE AFTERNOON AND EARLY EVENING HOURS AND THEN DECREASING AGAIN AFTER MIDNIGHT AS THE LOW PULLS AWAY TO THE NE. THERE WILL BE A SUBSTANTIAL GRADIENT OF POPS...WITH CHANCES RAPIDLY DECREASING AS ONE MOVES INLAND...AND WITH OUR FAR INLAND COUNTIES REMAINING DRY THROUGH THE PERIOD. QPF TOTAL FORECAST IS TRICKY AND WILL DEPEND UPON EXACT TRACK OF LOW. THE NAM IS THE MOST BULLISH IN THIS REGARD WITH A NEARLY SATURATED MOISTURE PROFILE LATE THIS AFTERNOON AND EVENING. DUE TO THE UNCERTAINTIES INVOLVED WILL BE ADOPTING A MIDDLE-GROUND APPROACH...WITH QPF EVENT TOTALS RANGING FROM BETWEEN A QUARTER AND A HALF AN INCH ALONG THE COAST TO ZERO WELL INLAND. MODEL SOUNDINGS ALSO INDICATE A TRANSITION IN PRECIP TYPE FROM MORE CONVECTIVE EARLY ON TO STRATIFORM OVERNIGHT. SEASONAL TEMPERATURES WILL PREVAIL. HAVE LEANED TOWARDS THE RECENTLY BETTER-PERFORMING GFS GUIDANCE FOR THIS PERIOD...WITH HIGHS IN THE LOWER 80S AND OVERNIGHT LOWS IN THE MID 60S FOR MOST PLACES.
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&& .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 300 AM SATURDAY...LOW PRESSURE MOVING JUST OFF THE COAST SUNDAY MORNING WILL RACE NORTHEAST THROUGH THE DAY. SUNDAY MORNING MAY STILL BE UNSETTLED WITH CLOUDS AND RAIN SHOWERS ALONG THE COAST...BUT RAPID DRYING WILL OCCUR ON N/NW WINDS DURING THE AFTN...AND THE SECOND HALF OF SUNDAY WILL LIKELY BE PRETTY NICE WITH LOTS OF SUNSHINE AND HIGHS IN THE LOW TO MID 80S. FORECAST PROFILES ARE VERY DRY SUNDAY NIGHT...BUT WINDS WILL BEGIN TO BACK TO THE SW AS HIGH PRESSURE RIDGES UP INTO THE AREA...AND THUS LOWS SUNDAY NIGHT WILL LIKELY BE A BIT ABOVE CLIMO...A DEGREE OR TWO EITHER SIDE OF 65. MONDAY WILL BE A TRANSITIONAL DAY...STARTING WARM BUT COOLING OFF LATE AS A COLD FRONT CROSSES THE AREA. FROPA IS NOW EXPECTED TO BE EARLY MONDAY...CROSSING OFFSHORE BY THE AFTN...BUT A STRONG VORT IMPULSE WILL ROTATE OVERHEAD ALONG OR JUST BEHIND THE COLD FRONT CAUSING SOME SHOWERS...PRIMARILY ALONG THE COAST. NO STRONG STORMS ARE EXPECTED...BUT PVA COMBINED WITH 300-500 J/KG OF SBCAPE WILL SUPPORT ISOLATED TSTMS BENEATH THIS VORT LOBE. VERY DRY AIR FLOODS IN BEHIND THIS FEATURE MONDAY NIGHT...USHERING IN ASTRONOMICAL FALL WHICH OCCURS AROUND 1030PM MONDAY NIGHT. HIGHS MONDAY WILL BE IN THE LOW 80S...WITH SOME MID 80S IN THE SOUTHEAST ZONES...FOLLOWED BY A COOL NIGHT AS LOWS DROP TO NEAR 60...OR SLIGHTLY BELOW FAR NW COUNTIES. && .LONG TERM /TUESDAY THROUGH FRIDAY/... AS OF 300 AM SATURDAY...THE EXTENDED BEGINS WITH BEAUTIFUL FALL WEATHER...WHICH IS APPROPRIATE SINCE TUESDAY IS THE FIRST FULL DAY OF ASTRONOMICAL FALL (EQUINOX ON MONDAY NIGHT). COLD FRONT WILL BE WELL OFFSHORE...WITH COOL CANADIAN HIGH PRESSURE BUILDING ACROSS MOST OF THE EAST COAST AND RIDGING DOWN INTO THE SOUTHEAST. WHILE THE FIRST HALF OF THE EXTENDED LOOKS QUITE GORGEOUS...WITH TEMPS JUST BELOW CLIMO AND LOW HUMIDITY...THERE IS SOME UNCERTAINTY LATE IN THE WEEK AS THE HIGH TAKES ON A WEDGE-TYPE SETUP ALLOWING FOR INCREASED LOW-LEVEL E/NE FLOW TO FLOOD INTO THE REGION. THIS WILL LIKELY PRODUCE ENHANCED LOW-LEVEL CLOUDINESS AND POSSIBLE SHOWERS...MAINLY ALONG THE COAST...LATE IN THE PERIOD. BEST CHANCE WILL BE ALONG THE EASTERN SC ZONES...BUT WILL FOLLOW THE INHERITED TREND OF RAISING SCHC POP THU/FRI FOR THE ENTIRE COAST ON D6/D7 WITH A MINOR DIURNAL ENHANCEMENT. && .AVIATION /10Z SATURDAY THROUGH WEDNESDAY/... NE WINDS WILL CONTINUE THROUGH THE TAF VALID PERIOD AS LOW PRESSURE DEVELOPING OVER THE BAHAMAS GRADUALLY STRENGTHENS AND THEN MOVES NE OFF THE EASTERN SEABOARD. SHOWER/THUNDERSTORM ACTIVITY WILL INCREASE TODAY AND TONIGHT...ESPECIALLY FOR THE COASTAL TERMINALS...AS THE LOW APPROACHES THE EASTERN CAROLINAS. A MORE STRATIFORM RAIN OF A PATCHY NATURE MAY DEVELOP AFTER SUNSET...WITH CONDITIONS GRADUALLY IMPROVING AFTER MIDNIGHT AS THE LOW PULLS NE AND AWAY FROM THE REGION. FOR NOW KEEPING FLO AND LBT DRY WITH CIGS NO LOWER THAN 4 KFT TODAY AND TONIGHT. FLO AND LBT MAY SEE PATCHY FOG THIS AM HOWEVER...WITH TEMPO GROUPS TO 4SM BEFORE DAYBREAK. EXTENDED OUTLOOK...GUSTY NORTHEAST WINDS WILL BECOME NORTHWEST AND DECREASE SUN AS LOW PRESSURE MOVES NE FURTHER AWAY FROM THE TERMINALS. OTHERWISE VFR SUN THROUGH WED WITH A CHANCE OF A SHOWER WITH A COLD FRONT ON MONDAY. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 630 AM SATURDAY...NO CHANGES TO THE FORECAST WITH THE LATEST UPDATE. PREVIOUS DISCUSSION FOLLOWS: A LOW PRESSURE CENTER DEVELOPING OVER THE BAHAMAS WILL MOVE NORTHEAST UP THE COAST AND WILL PASS EAST OF THE WATERS TONIGHT. PRESENT NE WINDS WILL BACK TO THE NORTH...BECOMING MORE OFFSHORE AFTER MIDNIGHT AS THE LOW MAKES ITS MOVE UP THE COAST. THESE OFFSHORE WINDS WILL ALLOW SEAS TO DROP BY A FOOT OR SO LATE IN THE PERIOD. THIS MAY ALLOW SEAS TO DECLINE BELOW THE 6 FT CRITERIA FOR THE SMALL CRAFT ADVISORY PRESENTLY IN EFFECT...BUT DUE TO UNCERTAINTY REGARDING EXACT TRACK AND DEVELOPMENT OF LOW...WILL BE KEEPING THE ADVISORY IN FORCE THROUGH THE PERIOD. SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 300 AM SATURDAY...3-5 FT SEAS WILL BOOKEND THE SHORT TERM...AS ELEVATED WINDS DRIVE HIGHER WAVE HEIGHTS BOTH SUNDAY MORNING AND THEN AGAIN MONDAY NIGHT. LOW PRESSURE MOVING WELL OFFSHORE WILL CREATE ELEVATED NORTHERLY WINDS OF 10-20 KTS THE FIRST HALF OF SUNDAY...BUT AS THIS SYSTEM PULLS OFF TO THE NORTHEAST...WINDS WILL BACK TO THE SW AND EASE TO AROUND 10 KTS. A COLD FRONT WILL CROSS THE WATERS MONDAY AFTN...TURNING WINDS QUICKLY TO THE NW BUT AT STILL RELATIVELY LIGHT SPEEDS...BEFORE A NE SURGE DEVELOPS AT THE END OF THE PERIOD DRIVING WINDS TO 15-20 KTS ONCE AGAIN AT THE END OF THE PERIOD. SEAS MUCH OF SUNDAY AND MONDAY WILL BE 1-3 FT WITH A VARIABLE SPECTRUM...WITH THE AFOREMENTIONED HIGHER SEAS BEING CONFINED TO THE FIRST AND LAST 6 HRS OF THE PERIOD. LONG TERM /TUESDAY THROUGH WEDNESDAY/... AS OF 300 AM SATURDAY...HIGH PRESSURE RIDGING DOWN THE EAST COAST WILL WORK IN TANDEM WITH A DEVELOPING COASTAL TROUGH THROUGH MID-WEEK TO PRODUCE AN EXTENDED PERIOD OF NE WINDS. THE NE SURGE THAT DEVELOPS JUST BEFORE THIS PERIOD WILL PERSIST...AND THEN STRENGTHEN AS THE GRADIENT TIGHTENS BY WEDNESDAY...DRIVING WINDS UP TO 20 KTS OR MORE BY WEDNESDAY. THIS EXTENDED PERIOD OF NE WIND WILL CAUSE DETERIORATING MARINE CONDITIONS...AND AN SCA WILL LIKELY BE NEEDED AS WAVE HEIGHTS RISE TO 6 FT OR MORE TUESDAY NIGHT AND WEDNESDAY.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT SUNDAY FOR AMZ250-252-254- 256. && $$ SYNOPSIS...JDW NEAR TERM...REK SHORT TERM...JDW LONG TERM...JDW AVIATION...REK MARINE...REK/JDW

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