Area Forecast Discussion
Issued by NWS Wilmington, NC

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021 FXUS62 KILM 201939 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 339 PM EDT WED MAY 20 2015 .SYNOPSIS...
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DEVELOPING LOW PRESSURE WILL SWEEP ACROSS NORTH CAROLINA ON THURSDAY PUSHING A COLD FRONT OFFSHORE BY THURSDAY EVENING. HIGH PRESSURE WILL BUILD IN FROM THE NORTH FRIDAY...BRINGING DRIER AIR INTO THE REGION OVER THE WEEKEND. THE HIGH WILL MOVE OFFSHORE SUNDAY INTO MONDAY BRINGING A RETURN OF HUMIDITY BY THE MIDDLE OF NEXT WEEK.
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&& .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... AS OF 200 PM WEDNESDAY...LINGERING FRONTAL BOUNDARY LOOKS LIKE IT WAS DRAPED JUST SOUTH OF THE BORDER ACROSS SOUTH CAROLINA. FAIRLY WELL DEFINED WHEN VIEWING VISIBLE SATELLITE WITH CU BUILDING ALONG AND SOUTH OF BOUNDARY IN MORE MOISTURE RICH AIR MASS. LARGE DEWPOINT GRADIENT ACROSS THE REGION FROM NORTH TO SOUTH ON EITHER SIDE OF FRONT...DEW POINT TEMPS ACROSS CENTRAL NC DOWN BELOW 60 WHILE HEADING SOUTH DEWPOINTS UP NEAR 70. OVERALL NOT A HUGE CHANGE IN AIR MASS AS CAA IS LACKING WITH MAINLY ZONAL WESTERLY DOWNSLOPE FLOW ALOFT ALLOWING BOUNDARY TO MEANDER OVER SOUTH CAROLINAS JUST SOUTH OR NEAR LOCAL FORECAST AREA. TEMPS WERE UP TO THE MID 80S IN DRIER AIR TO THE NORTH AND UP AROUND 90 OVER MOST OF SOUTH CAROLINA...UNDER PLENTY OF SUNSHINE. ASIDE FROM A PATCH OF MID LEVEL CLOUDS OVER THE LUMBERTON AREA...BETTER SUBSIDENCE AND DRIER AIR TO THE NORTH WILL KEEP A GREATER AMOUNT OF SUNSHINE THROUGH THIS AFTERNOON. WEAK GRADIENT FLOW WILL ALLOW A SEA BREEZE TO DOMINATE THE FLOW WITH ON SHORE WINDS. THIS WILL HELP BRING MOISTURE BACK OVER THE AREA AND WILL PROVIDE ENOUGH CONVERGENCE TO GENERATE SOME ISOLATED PULSE TYPE CONVECTION. ANOTHER FOCUS OF CONVECTION WILL BE ALONG WEAKENING FRONT THROUGH TONIGHT...WITH MORE WIDESPREAD DIURNALLY DRIVEN CONVECTION ALONG AND SOUTH THROUGH THIS AFTERNOON. THE BEST LIFT AND MOISTURE WILL REMAIN SOUTH OF LOCAL FORECAST AREA BUT RESIDUAL MOISTURE CLOSER TO THE COAST WILL COMBINE WITH CONVERGENCE ALONG THE SEA BREEZE AS IT PUSHES SLOWLY INLAND AND THE LINGERING FRONT OVER COASTAL SC TO PRODUCE SOME STORMS...MAINLY OVER GEORGETOWN AND WILLIAMSBURG COUNTIES AND ALONG INTERIOR OF COASTAL COUNTIES UP TO CAPE FEAR. THE STEERING FLOW IS OUT OF THE WEST AROUND 10 KT AND WILL PUSH ANY DEBRIS CLOUDS OR STORMS THAT DEVELOP EAST TOWARD THE COAST. ONCE HEATING OF THE DAY CUTS OFF THIS EVENING THE SHWRS/TSTMS WILL DISSIPATE FOR THE MOST PART. A SHORTWAVE WILL APPROACH THE CAROLINAS SPINNING UP A SFC LOW WHICH WILL RIDE EAST TOWARD THE MORNING. THIS WILL PROVIDE A BACKING OF WINDS TO THE S-SW OVER EASTERN CAROLINAS THROUGH TONIGHT...LIFTING BOUNDARY FARTHER NORTH. BEST CONVERGENCE AND PCP WILL REMAIN OFF THE COAST OVERNIGHT IN CONVERGENCE ALONG THE BOUNDARY. BEST MID TO UPPER LEVEL SUPPORT WILL REMAIN WEST-NORTHWEST OF AREA BUT MAY SEE SOME SHOWERS DEVELOP TO THE WEST AFTER MIDNIGHT. AS WINDS BECOME MORE ON SHORE AND SOUTHERLY OVERNIGHT MINIMUMS SOME SHOWERS MAY MOVE ON SHORE. IT REMAIN MILD FROM MID 60S WELL INLAND TO AROUND 70 COASTAL ZONES. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
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~50 MILES FARTHER SOUTH WHICH WOULD SHIFT THE BEST POTENTIAL FOR STORMS INTO THE BENNETTSVILLE-WHITEVILLE-WILMINGTON CORRIDOR. A FIRST-GLANCE AT THE NEW 12Z ECMWF SHOWS IT NOW HAS THE LOW TRACKING ALMOST AS FAR NORTH AS THE 12Z GFS/NAM MODELS...HOPEFULLY KEEPING THE CORRIDOR OF BEST SEVERE WEATHER POTENTIAL JUST TO OUR NORTH. THURSDAY NIGHT AND FRIDAY SHOULD BE QUIET AND UNEVENTFUL AS DRIER AND COOLER AIR ARRIVES ON NORTHERLY WINDS. SURFACE HIGH PRESSURE CENTERED TO OUR WEST WILL BUILD IN THROUGH THE WEEKEND. I HAVE ADJUSTED FORECAST TEMPERATURES DOWNWARD BY A FEW DEGREES AS LATEST MODELS SHOW NEAR-IDEAL RADIATIONAL COOLING CONDITIONS OCCURRING IN AN UNSEASONABLY CHILLY AIRMASS.
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&& .LONG TERM /SATURDAY THROUGH WEDNESDAY/...
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AS OF 300 PM WEDNESDAY...WITH DRY SFC HIGH PRESSURE AND DECENT RIDGING IN PLACE...EXPECT A FAIRLY QUIET PERIOD INTO EARLY NEXT WEEK. WILL SEE A GRADUAL INCREASE OF TEMPERATURES THROUGH THE MEMORIAL DAY WEEKEND FROM LOW/MID 80S TO MID/UPPER 80S ON MONDAY...WITH OVERNIGHT LOWS IN THE LOW TO MID 60S. AS SFC HIGH PRESSURE BEGINS TO SHIFT OFFSHORE...WILL SEE A NICE MOISTURE RETURN BEGINNING AS EARLY AS MONDAY. WITH HIGH TEMPERATURES IN THE MID TO UPPER 80S ON TUESDAY AND INCREASING HUMIDITY...COULD SEE SOME ISOLATED TO SCATTERED SHOWERS IN THE AFTERNOON HOURS...WITH A THUNDERSTORM POSSIBLE...MAINLY INLAND. INTO WEDNESDAY...PRECIPITABLE WATER VALUES INCREASE TO OVER ONE AND A HALF INCHES...AND AHEAD OF AN APPROACHING COLD FRONT ON WEDNESDAY. TIME OF ARRIVAL OF THE FRONT ITSELF IS HARD TO DETERMINE ATTM AS SOME GUIDANCE SUGGESTS ITS PROGRESSION MAY SLOW DOWN GIVEN WEAK RIDGING STILL IN PLACE. FOR NOW HAVE CONTINUED SLIGHT CHANCE FOR SHOWERS/THUNDERSTORMS ON WEDNESDAY. WITH OVERNIGHT LOWS INTO WEDNESDAY MORNING IN THE UPPER 60S...WILL SEE HIGH TEMPERATURES IN THE MID 80S ALONG THE COAST...AND UPPER 80S INLAND...WITH A FEW SPOTS POTENTIALLY HITTING 90 DEGREES.
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&& .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... AS OF 18Z...QUITE A BIT OF UNCERTAINTY AS MANY OF THE FEATURES OVER THE NEXT 24 HOURS ARE SUBTLE AS WE HEAD INTO AN EARLY SUMMER PATTERN. WITH ALL THE HEATING AND LOW LEVEL MOISTURE...THINK THE SEA BREEZE BOUNDARY WILL BE QUITE ACTIVE...PARTICULARLY OVER SOUTH CAROLINA. NEW HANOVER AND PENDER COUNTIES DID HAVE QUITE A BIT OF RAIN SO THEY COULD GET INTO THE ACT ALSO. BRIEF ROUNDS OF IFR ARE POSSIBLE IN THE HEAVIEST SHOWERS. LOOK FOR THE CONVECTION TO DIE DOWN BY EVENING...HOWEVER ANOTHER ROUND OF SHOWERS IS POSSIBLE TOWARD MORNING AS YET ANOTHER IMPULSE MOVE IN FROM THE WEST. EXTENDED OUTLOOK...ISOLATED TO SCATTERED SHOWERS/THUNDERSTORMS POSSIBLE ON THURSDAY. OTHERWISE EXPECT VFR. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 200 PM WEDNESDAY...FAIRLY TRANQUIL MARINE CONDITIONS CONTINUE AS WEAKENING FRONT REMAINS DRAPED ACROSS SOUTH CAROLINA INTO THE ATLANTIC WATERS NEAR OR JUST SOUTH OF LOCAL WATERS. GRADIENT FLOW REMAINS VERY WEAK ALLOWING THE SEA BREEZE TO DOMINATE THE WINDS NEAR SHORE...KEEPING ONSHORE AND SLIGHTLY GUSTIER WINDS CLOSER TO THE COAST...LESS THAN 10 KTS MOST WATERS. SEAS BASICALLY LESS THAN 3 FEET THROUGH MOST OF THE NIGHT ALTHOUGH EXPECT A SLIGHT UPTICK AFTER MIDNIGHT AS WINDS INCREASE SLIGHTLY OUT OF THE S-SW AS GRADIENT TIGHTENS A BIT TOWARD MORNING AS DEVELOPING LOW PRESSURE APPROACHES THE CAROLINAS FROM THE WEST. SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... AS OF 300 PM WEDNESDAY...LOW PRESSURE WILL MOVE EASTWARD THROUGH NORTH CAROLINA THURSDAY...BRINGING A BELT OF SOUTHWEST 15-20 KT WINDS THROUGH THE AREA. A COLD FRONT WILL DIP SOUTH BEHIND THE DEPARTING LOW THURSDAY EVENING...WITH NORTHERLY WINDS EXPECTED THROUGH FRIDAY. THE STRONGEST NORTH WINDS ARE EXPECTED THURSDAY NIGHT INTO EARLY FRIDAY WITH 15-20 KT POSSIBLE AT TIMES. THESE PERIODS OF RELATIVELY STRONG WINDS SHOULD LAST LESS THAN 12 HOURS EACH...AND THEREFORE SEAS ARE EXPECTED TO REMAIN BELOW 5 FEET. LONG TERM /SATURDAY THROUGH MONDAY/... AS OF 330 PM WEDNESDAY...HIGH PRESSURE WILL RESULT IN NE WINDS OF 10 TO 15 KT SATURDAY WHICH WILL VEER TO THE SE BY SUNDAY NIGHT. SEAS OF 3 FT OR LESS ARE ON TAP FOR THE PERIOD.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ NEAR TERM...RGZ SHORT TERM...TRA LONG TERM...SGL AVIATION...DL

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