Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 170519 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 119 AM EDT WED SEP 17 2014 .SYNOPSIS... A COLD FRONT WILL PUSH OFFSHORE LATE TONIGHT. HIGH PRESSURE WILL EXTEND DOWN INTO THE CAROLINAS FROM THE NORTH BEHIND THIS FRONT...PROVIDING FALL-LIKE WEATHER FOR THE REMAINDER OF THE WEEK. THE NEXT COLD FRONT WILL MOVE THROUGH BY MONDAY NIGHT. && .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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AS OF 1:30 AM WEDNESDAY...LINE OF CONVECTION DROPPING FROM THE NORTH BREAKING UP TO SOME EXTENT AND IS NOT AS STRONG/SOLID AS BEFORE. THIS TREND WILL CONTINUE UNTIL ACTIVITY MOVES OFFSHORE IN THE EARLY MORNING HOURS. PREVIOUS DISCUSSION FOLLOWS: QUITE A LINE OF CONVECTION HAS DEVELOPED OVER THE PAST FEW HOURS EXTENDING FROM THE SOUTH SIDE OF CHARLOTTE EASTWARD ACROSS ROCKINGHAM...FAYETTEVILLE...AND APPROACHING CLINTON. SPC MESOANALYSIS INDICATES SURFACE-BASED PARCELS ARE CAPPED...WHICH MAKES SENSE GIVEN SURFACE TEMPERATURES IN THE LOWER 70S. ELEVATED CAPE OF 750-1000 J/KG WITH MINIMAL CAPPING IS AVAILABLE WHEN PARCELS AROUND 950-925 MB ARE CONSIDERED. MID-LEVEL LAPSE RATES ARE RATHER STEEP AT 6 DEG C/KM. ALTHOUGH CONVECTION HAS MERGED INTO A LINE EARLIER THERE WERE HINTS OF SUPER CELLULAR CHARACTERISTICS AS A BELT OF STRONGER MID-LEVEL FLOW ACROSS NORTH- CENTRAL NORTH CAROLINA IS PRODUCING 0-6 KM BULK SHEAR VALUES NEAR 30 KNOTS. THE SURFACE COLD FRONT IS LOCATED 50-100 MILES BEHIND THE CONVECTION...CURRENTLY EXTENDING ACROSS THE NORTHERNMOST ROW OF COUNTIES IN NORTH CAROLINA. ALTHOUGH PRESSURES ARE CURRENTLY STEADY ACROSS THE AREA WE ANTICIPATE FALLING PRESSURES TO DEVELOP ALONG THE COAST AND OFFSHORE SHORTLY AS LOW PRESSURE DEVELOPS. THIS LOW WILL PULL THE FRONT DOWN LATE TONIGHT AND OFFSHORE BY DAYBREAK. SINCE THE CONVECTION IS ELEVATED AND BASED WITHIN A UNIFORM 950-900 MB LAYER IT SHOULD RESPOND MORE TO OVERALL SYNOPTIC FORCING THAN TO ANYTHING GOING ON HERE AT THE SURFACE. THE UPPER DISTURBANCE IS LOCATED NEAR I-77 NORTH OF CHARLOTTE AND SHOULD MOVE EAST-NORTHEASTWARD THROUGH THE NIGHT. AS THE STORMS DRIFT SOUTH THEY WILL MOVE OUT OF THE INFLUENCE OF THE UPPER TROUGH AND SHOULD WEAKEN. THIS IS SHOWN BY THE 23Z RUN OF THE HRRR...WHICH ALSO INDICATES THE CONVECTION MAY JUMP WILMINGTON AND SOUTHPORT...REDEVELOPING OFFSHORE AFTER 2-3 A.M. WITHIN A REGION OF SURFACE-BASED INSTABILITY OVER THE WARM OCEAN WATER. NO CHANGES HAVE BEEN MADE TO FORECAST LOWS...STILL ANTICIPATED TO RANGE FROM THE UPPER 60S INLAND TO THE LOWER 70S AT THE COAST.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH THURSDAY NIGHT/... AS OF 300 PM TUESDAY...WEAK LOW PRESSURE ALONG LINGERING FRONT WILL GET PUSHED FARTHER OFF SHORE AS HIGH PRESSURE BUILDS DOWN FROM THE NORTHWEST THROUGH MID WEEK. THE EASTERLY FLOW AROUND THE TOP OF THE LOW WILL COME UP AGAINST W-NW FLOW AS HIGH PRESSURE BUILDS IN. THIS WILL PRODUCE SOME LOW LEVEL CONVERGENCE THROUGH WED AND THE LAST BIT OF ENERGY IN THE MID LEVELS WILL ROUND THE BASE OF THE TROUGH BEFORE IT LIFTS OFF TO THE NORTHEAST. THEREFORE WILL KEEP SOME CLOUDS AND POPS IN FORECAST ON WED. THE MID TO UPPER TROUGH RUNNING DOWN THE EAST COAST WILL SHIFT SLOWLY EAST AND WILL LIFT FARTHER OFF TO THE NORTHEAST WED INTO THURS. AS TROUGH AXIS CROSSES THE COAST EARLY THURS...A DEEPER N-NW FLOW WILL ESTABLISH ITSELF OVER THE CAROLINAS WITH CONSIDERABLE DRYING AND SUBSIDENCE THROUGH THE MID LEVELS. HIGH PRESSURE WILL BUILD IN WITH LIGHT NORTHERLY WINDS VEERING AROUND TO THE NE THROUGH LATE THURS. PCP WATER VALUES DROP FROM AROUND 1.5 INCHES WED AFTN DOWN CLOSER TO AN INCH BY THURS EVE. DEWPOINT TEMPS IN THE MID TO UPPER 60S WED AFTN WILL DROP INTO THE LOWER 60S THROUGH THURS. OVERALL EXPECT CONDITIONS TO IMPROVE WITH INCREASING SUNSHINE AND MORE FALL LIKE WEATHER. AS AIR MASS TRANSITIONS TO A DRIER MORE SEASONABLE AIR MASS...SO WILL THE TEMPS. TEMPS OVERNIGHT WED WILL BE WARMER THAN THURS NIGHT BY A COUPLE OF DEGREES...MID 60S BOTH NIGHTS. TEMPS WILL REACH INTO THE 80S ON WED BUT ON THURS TEMPS WILL RUN A FEW DEGREES COOLER EVEN WITH A GREATER AMOUNT OF SUNSHINE. && .LONG TERM /FRIDAY THROUGH TUESDAY/... AS OF 300 PM TUESDAY...ON FRIDAY A LARGE AREA OF COOL HIGH PRESSURE WILL BE SLIDING EAST ACROSS NEW ENGLAND. THIS ANTICYCLONE WILL HAVE A RIDGE AXIS EXTENDING ALL THE WAY DOWN INTO THE CAROLINAS. FLOW ALOFT WILL BE VERY WEAK BUT STILL HAVE SOME SENSE OF TROUGHINESS. MODELS HAVING A HARD TIME TELLING HOW MUCH THIS TROUGHINESS ERODES THE EASTERN PERIPHERY OF THE SURFACE RIDGE. THE MORE AGGRESSIVE GFS MANAGES TO FLING MOISTURE ASHORE AND HAS THE SUPPORT OF THE CMC. THE (00Z) ECMWF DOES THE SAME BUT WITH A MUCH SLOWER SENSE OF TIMING KEEPING MOST PLACES DRY TIL SUNDAY. WILL SHOW JUST SLIGHT CHANCE POPS ALONG THE COAST THROUGH THESE DAYS. THE WEDGE APPEARS TO WASH OUT BY MONDAY AT WHICH TIME RAIN CHANCES SHIFT TO BEING TIED TO A DEVELOPING PIEDMONT TROUGH AND TEMPS REBOUND TO NORMAL OR HIGHER. A COLD FRONT APPEARS SLATED FOR A MONDAY NIGHT ARRIVAL. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
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AS OF 06Z...THE HRRR SUGGESTS SLOW-MOVING SHOWER/TSTM ACTIVITY ALONG THE COLD FRONT MAY STILL PLAGUE OUR INLAND TAF SITES AT THE START OF THE PERIOD. THEREFORE WILL INCLUDE VCSH FOR KFLO/KLBT FROM 06-08Z. INCREASING DEBRIS CLOUDS FROM FRONTAL CONVECTION WILL LIKELY LIMIT FOG POTENTIAL OVERNIGHT. HAVE JUST INCLUDED TEMPO MVFR VSBYS... MAINLY EARLY IN THE PERIOD AS THE NORTHEASTERLY SURGE AFTER 09Z OR SO SHOULD MIX OUT ANY LINGERING BR. COULD ALSO SEE SOME MVFR CIGS DEVELOP BEHIND THE FRONT THIS MORNING...BUT IFR POTENTIAL APPEARS LOW EVEN FOR THE INLAND TERMS. MVFR CIGS COULD LINGER THROUGH THE LATE MORNING HOURS BEFORE IMPROVING TO VFR BY MIDDAY. EXPECT NE WINDS AOB 10 KT BEHIND THE FRONT TO PERSIST THROUGH THE PERIOD. EXTENDED OUTLOOK...EARLY MORNING MVFR/IFR CIGS POSSIBLE ON THU. GUSTY NORTHEAST WINDS EXPECTED FRI/SAT AS THE COOL AIR WEDGE STRENGTHENS OVER THE CAROLINAS. VFR ON SUNDAY.
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&& .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 1:30 AM WEDNESDAY...NO CHANGES TO THE FORECAST WITH THE LATEST UPDATE. PREVIOUS DISCUSSION FOLLOWS: WINDS ACROSS THE NC WATERS ARE GENERALLY FROM THE SOUTH OR SOUTHEAST WITH A MORE VARIABLE PATTERN NOTED ACROSS THE SOUTH CAROLINA WATERS. PRESSURES SHOULD BEGIN TO FALL SHORTLY ALONG THE COAST AS LOW PRESSURE DEVELOPS OFFSHORE. THIS LOW WILL PULL THE COLD FRONT...CURRENTLY ACROSS NORTHERN NORTH CAROLINA...SOUTHWARD AND OFF THE COAST BY DAYBREAK WITH NORTHERLY WINDS EXPECTED TO DEVELOP. A LINE OF THUNDERSTORMS ACROSS THE INTERIOR COASTAL PLAIN WILL PROBABLY WEAKEN BEFORE MAKING IT TO THE BEACHES...HOWEVER CONDITIONS FAVOR THE DEVELOPMENT OF SCATTERED THUNDERSTORMS OUT AHEAD OF THIS LINE AFTER MIDNIGHT...MOST LIKELY IN THE 2-4 AM TIME FRAME. SEAS CURRENTLY 1-2 FT MAY BEGIN TO BUILD TOWARD 3 FEET ACROSS THE OUTERMOST PORTION OF THE COASTAL WATERS LATE TONIGHT AS SWELL FROM DISTANT HURRICANE EDOUARD FINALLY MAKES IT TO THE COAST. SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... AS OF 300 PM TUESDAY...WILL MAINTAIN E-NE WINDS THROUGH MID WEEK AS HIGH PRESSURE BUILDS DOWN FROM THE NORTH. INITIALLY WINDS WILL BE LIGHTER AND MORE EASTERLY. THE ON SHORE FLOW UP TO 10 KTS ON WED WILL COMBINE WITH THE SEA BREEZE AND A LONG PERIOD UP TO 16 SEC EASTERLY SWELL TO PUSH SEAS UP TO 2 TO 4 FT WITH SOME 5 FTERS IN OUTER WATERS WED AFTN. THE LONGER PERIOD EASTERLY SWELLS FROM EDOUARD WELL OUT IN THE ATLANTIC WATERS WILL PEAK AROUND 16 SECONDS VERY EARLY WED AND WILL DIMINISH SLOWLY THROUGH THURS. SEAS WILL ACTUALLY DROP SLIGHTLY THROUGH EARLY THURS BUT A SLIGHT INCREASE IN NE WINDS UP TO 10-15 KNOTS THROUGH THUR NIGHT SHOULD PRODUCE ANOTHER SPIKE IN SEAS BY FRI MORNING. LONG TERM /FRIDAY THROUGH SUNDAY/... AS OF 300 PM TUESDAY...A WEDGE OF HIGH PRESSURE MORE REMINISCENT OF THE COOL SEASON WILL DEVELOP ON FRIDAY. THE PINCHED NORTHEASTERLY GRADIENT COULD YIELD A FEW ADVISORY-WORTHY 6 FT SEAS INTO NRN ZONES...BUT WNA GUIDANCE HAS COME DOWN FROM PREVIOUS RUNS AND IT MAY BE QUITE MARGINAL. CURRENT FCST STILL SHOWING A RAMP UP TO 4 TO 6 THOUGH. WAVE SHADOWING WILL PRECLUDE ADVISORY OVER SOUTHERN WATERS. A MODERATE NORTHEASTERLY FLOW WILL REMAIN IN PLACE FOR THE REST OF THE PERIOD WITH A GRADUAL DECREASE IN STRENGTH. BORDERLINE SCEC/ADVISORY MAY CONTINUE OVER NRN ZONES INTO SATURDAY. FURTHER WEAKENING OF THE HIGH PRESSURE WILL BRING QUIETER CONDITIONS COME SUNDAY.
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&& .ILM WATCHES/WARNINGS/ADVISORIES...
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SC...NONE. NC...NONE. MARINE...NONE.
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&& $$ SYNOPSIS...RGZ NEAR TERM...REK/RJD/TRA SHORT TERM...RGZ LONG TERM...MBB AVIATION...BJR MARINE...REK/RJD/TRA/MBB/RGZ

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