Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 300520 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 120 AM EDT TUE SEP 30 2014 .SYNOPSIS...
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LOW PRESSURE OFF THE SOUTHEAST UNITED STATES COAST WILL MOVE FARTHER OFFSHORE THROUGH TODAY. WEAK HIGH PRESSURE WILL BUILD ACROSS THE CAROLINAS THROUGH THURSDAY. A STRONG COLD FRONT WILL PUSH ACROSS THE AREA EARLY SATURDAY ACCOMPANIED BY THE NEXT CHANCE OF SHOWERS AND THUNDERSTORMS. MUCH COOLER FALL WEATHER IS EXPECTED EARLY NEXT WEEK.
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&& .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
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AS OF 1045 PM MONDAY...LATEST 88D TRENDS ILLUSTRATE THE MAIN RAIN SHIELD HAS MOVED OFF THE CAROLINA COASTS. THIS LEAVES PATCHY LIGHT RAIN AND DRIZZLE FOR THE PRE-DAWN HOURS. PLENTY OF MOISTURE THRU THE LOWER LEVELS OF THE ATM COLUMN AND AM HESITANT TO PLACE FOG IN THE FCST. WINDS ALONG THE IMMEDIATE COAST SHOULD STAY ACTIVE VIA THE LOW DEVELOPING OFFSHORE FROM GA-SC COASTS. HAVE KEPT A STRATUS CLOUD DECK THRUOUT THE OVERNIGHT...AND UP THRU SEVERAL HOURS AFTER DAYBREAK TUE. THIS SHOULD ALSO HOLD THE FOG TO A MINIMUM. MIN TEMP FCST STILL IN THE BALLPARK AND SEE NO REASON TO TWEAK. PREVIOUS DISCUSSION........................................... AS OF 730 PM MONDAY...BASED ON LATEST RADAR TRENDS...THE PCPN CONSISTING OF LIGHT RAIN OR DRIZZLE...IS COMING TO AN END FROM WSW TO ENE ACROSS THE EASTERN CAROLINAS. LATEST HRRR ALSO ILLUSTRATES THE MAIN PCPN SHIELD SHOULD BE OFF THE COAST BY 1AM TO 3AM TUESDAY...LEAVING PATCHY LIGHT RAIN OR DRIZZLE FOR THE REMAINDER OF THE PRE-DAWN TUE HOURS. POPS FOR THE OVERNIGHT PERIOD HAVE BEEN RE-CALCULATED AS A RESULT. BECAME MORE PESSIMISTIC WITH ANY CLEARING DUE TO PLENTY OF MOISTURE AVBL FROM THE SFC THRU 600 MB AS SHOWN BY THE LATEST NAMBUFR SOUNDINGS ACROSS THE FA...WELL AFTER THE TIME PCPN COMES TO AN END. VERY LITTLE TWEAKING TO TONIGHTS MINS NEEDED.
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&& .SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/... AS OF 300 PM MONDAY...AN UPPER LEVEL TROUGH WILL BE MOVING OFF THE CAROLINA COAST AROUND DAYBREAK TUESDAY...WITH A DRY PUNCH IN THE MID LEVELS SCOURING OUT ALL THE MOISTURE ABOVE 700 MB. A FLAT UPPER RIDGE WILL BUILD INTO THE REGION WEDNESDAY. CLOCKWISE CIRCULATION AROUND SURFACE LOW PRESSURE (MOVING EAST THROUGH THE GEORGIA OFFSHORE WATERS) WILL KEEP NORTHEAST WINDS IN THE LOW LEVELS WITH ONLY A GRADUAL DRYING/CLEARING TREND EXPECTED. ALONG THE COAST THIS MEANS IT MAY TAKE UNTIL EARLY AFTERNOON FOR LOW CLOUDS TO BREAK...BUT INLAND SKIES SHOULD TURN PARTLY CLOUDY DURING THE MORNING WITH MOSTLY SUNNY CONDITIONS DURING THE AFTERNOON. ALTHOUGH THE 12Z GFS LOOKS MOST REASONABLE WITH MASS FIELDS IT MAY BE A LITTLE AGGRESSIVE CLEARING CLOUDS ALONG THE COAST AND I HAVE TRENDED MY FORECAST HIGHS A LITTLE BENEATH THE 12Z GFS MOS AS A RESULT...79-81 OVER SE NORTH CAROLINA AND 80-82 OVER NE SOUTH CAROLINA. MOISTURE TRAPPED UNDER A MODEST SUBSIDENCE INVERSION MAY LEAD TO A FEW EVENING CLOUDS BUT SKIES SHOULD BECOME CLEAR BEFORE MIDNIGHT. BOUNDARY LAYER WINDS MAY BE A TOUCH TOO STRONG FOR FOG ALTHOUGH THE MOISTURE PROFILES OTHERWISE LOOK PRETTY GOOD FOR FOG. LOWS SHOULD FALL TO AROUND 60 INLAND...WITH LOWER 60S COASTAL AREAS AND SOME MID 60S ON THE BEACHES. WITH EVEN LESS BOUNDARY LAYER MOISTURE (PRECIP WATER VALUES 0.8 TO 0.9 INCHES) EXPECTED ON WEDNESDAY SKIES SHOULD BE ESSENTIALLY CLEAR. LIGHT NORTHEAST WINDS WILL VEER SOUTHEASTERLY ALONG THE COAST WITH A LIGHT SEABREEZE CIRCULATION. HIGHS SHOULD REACH THE MID 80S ACROSS THE SC PEE DEE REGION...LOWER 80S ELSEWHERE EXCEPT A LITTLE COOLER AT THE BEACHES WHERE WATER TEMPERATURES HAVE BEGUN THEIR SEASONAL DROP...NOW IN THE MID-UPPER 70S. VERY LIGHT WINDS EXPECTED WEDNESDAY NIGHT WOULD ARGUE FOR FOG...BUT BOUNDARY LAYER MOISTURE MAY NOT BE QUITE DEEP ENOUGH ACCORDING TO THE 12Z MODEL SUITE. LOWS SHOULD FALL INTO THE LOWER 60S WITH MID-UPPER 60S AT THE BEACHES. && .LONG TERM /THURSDAY THROUGH MONDAY/... AS OF 300 PM MONDAY...DEEP MID LEVEL TROUGHING WILL BE THE MAIN STORY FOR THE EXTENDED FORECAST BEGINNING FRIDAY THROUGH THE WEEKEND. THIS FEATURE WILL ALLOW A COLD FRONT TO MOVE ACROSS THE AREA LATE FRIDAY/EARLY SATURDAY WITH DECENT FORCING AND WITH GUIDANCE SHOWING AN EVEN DEEPER TROUGH...MOISTURE ADVECTION FROM THE ATLANTIC IS STRONGER HENCE SLIGHTLY HIGHER POPS FOR THE EVENT. WITH THE TROUGH GOING A LITTLE NEGATIVE TILT...THE FRONT MAY SLOW BEFORE CLEARING OUT SATURDAY AND HAVE EXTENDED POPS A BIT TO ADDRESS. SUNDAY AND MONDAY SHOULD BE VERY NICE UNDER SURFACE HIGH PRESSURE. WE SHOULD SEE HIGHS IN THE 70S SATURDAY THROUGH MONDAY WITH LOWS IN THE 50S CWA WIDE. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/...
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AS OF 05Z...THE -RA FROM EARLIER TONIGHT HAS MOSTLY PUSHED OFFSHORE...AND THE MID LEVEL CLOUDS SHOULD GRADUALLY THIN OVERNIGHT AS THE UPPER TROUGH MOVES OVERHEAD AND OFF THE COAST. SURFACE OBS INDICATE FOG IS DEVELOPING OVER THE CENTRAL CAROLINAS WHERE THE WINDS HAVE GONE CALM AND THE MID LEVEL CIGS ARE NO MORE. THEREFORE...HAVE ADDED TEMPO IFR VSBYS FOR KLBT/KFLO EARLY THIS MORNING. THIS TREND FOLLOWS SOME OF THE LATEST HRRR RUNS SHOWING FOG/STRATUS EXPANDING INLAND AFTER 09Z. STILL THINK THE DEVELOPING LOW OFF THE SOUTHEAST COAST WILL KEEP WINDS AT THE COASTAL TERMINALS STRONG ENOUGH TO PREVENT ANY FOG...BUT SOME TEMPO IFR CIGS CANNOT BE RULED OUT BY DAYBREAK. WILL KEEP SCT 500 FT STRATUS AT THE COAST ATTM. DURING THE DAY... DRIER AIR BEHIND THE UPPER TROUGH WILL ALLOW VFR CONDITIONS TO DEVELOP AND PERSIST FOR THE REST OF THE TAF PERIOD. EXPECT NORTHEAST WINDS AOB 10 KT DURING THE DAY...BECOMING LIGHT/VRB AFTER 00Z WED. EXTENDED OUTLOOK...VFR CONDITIONS WILL PREVAIL THROUGH FRI. CHANCE OF SHOWERS/MVFR LATE FRI/EARLY SAT WITH A STRONG COLD FRONT.
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&& .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 1045 PM MONDAY...CURRENTLY A BROAD LOW EXTENDS OFF THE GA-FL COASTS FROM NE GULF OF MEXICO. MODELS CONTINUE TO PAINT A DEVELOPING SFC LOW OFFSHORE AND EAST OF THE GA COAST BY DAYBREAK TUE. THIS WILL RESULT IN A SFC PRESSURE PATTERN AND GRADIENT ACROSS THE ILM WATERS THAT WILL YIELD NE 10-20 KT OVERNIGHT INTO DAYLIGHT TUE. THE HIGHER END OF THIS SCALE TO OCCUR CLOSER TO THE LOW...OVER THE ILM SC WATERS. SIGNIFICANT SEAS IN THE 2 TO 4 FT RANGE...EXCEPT UP TO 5 FT OVER THE SOUTHERNMOST ILM SC WATERS. FOUR TO 6 SECOND PERIOD...WIND DRIVEN WAVES TO DOMINATE THE SIGNIFICANT SEAS. PREVIOUS DISCUSSION.............................................. AS OF 745 PM MONDAY...COASTAL TROF OR FRONT TO REMAIN OVER THE OFFSHORE WATERS JUST EAST OF THE COASTAL WATERS OVERNIGHT. WEAK SFC LOW TO MOVE OFF THE GA-FL COAST EARLY THIS EVENING...AND MOVE ENE ALONG THIS BOUNDARY OVERNIGHT STAYING OFFSHORE TO A POSITION OF 140NM SOUTH OF CAPE FEAR BY DAYBREAK TUE. THE LOW WILL STRENGTHEN-SOME AND HAVE AN EFFECT ON THE LOCAL WINDS...ESPECIALLY ACROSS THE ILM SC WATERS. FOR NOW WILL FORECAST A SOLID 10-15 KT BUT MAY INCREASE TO A SOLID 15 KT OR A 15-20 KT RANGE FOR THE ILM SC WATERS. SIGNIFICANT SEAS WILL RANGE IN THE 2 TO 4 FT...HIGHEST OFF CAPE FEAR AND OFF FROM THE MOUTH OF WINYAH BAY. FIVE FOOTERS ARE A POSSIBILITY OVER THE SOUTHERNMOST WATERS...WILL MONITOR. LOOKING AT 4 TO 5 SECONDS FOR AVERAGE PERIODS. SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... AS OF 300 PM MONDAY...LOW PRESSURE WILL DEEPEN TUESDAY MORNING OFF THE GEORGIA COAST ALONG AN OLD FRONT. AS THIS LOW MOVES AWAY FROM THE COASTLINE WEAK HIGH PRESSURE WILL BUILD SOUTHWARD ACROSS THE CAROLINA COASTAL WATERS...REMAINING IN PLACE THROUGH WEDNESDAY NIGHT. THIS MEANS AFTER THE INITIAL SURGE OF NORTH-NORTHEASTERLY WINDS TUESDAY...CONDITIONS SHOULD IMPROVE MARKEDLY FOR THE REMAINDER OF THE PERIOD. THE STRONGEST WINDS...NC AROUND 15 KNOTS WITH GUSTS TO 18-20 KNOTS...ARE EXPECTED TO BEGIN DIMINISHING AROUND SUNSET TUESDAY EVENING. LIGHTER NORTHEASTERLY WINDS SHOULD DOMINATE THROUGH THE PERIOD...EXCEPT WEDNESDAY AFTERNOON WHEN A WEAK SEABREEZE SHOULD TURN WIND DIRECTIONS MORE SOUTHEASTERLY. SEAS 3-4 FEET TUESDAY WILL DIMINISH TO AROUND 2 FEET. AMONG THE VARIOUS MODEL SOLUTIONS THE 12Z GFS LOOKS THE BEST FOLLOWED BY THE 00Z ECMWF. LONG TERM /THURSDAY THROUGH SATURDAY/... AS OF 300 PM MONDAY...VERY LIGHT WIND FIELDS THURSDAY WILL GIVE WAY TO STRONGER WINDS FRIDAY AND SATURDAY. SURFACE HIGH PRESSURE WILL BE WEAKENING THURSDAY AND EAST WINDS WILL TURN TO SOUTHEAST LATE. WIND SPEEDS WILL BE TEN KNOTS OR LESS. BY MIDDAY FRIDAY...THE SOUTHERLY FLOW WILL PICK UP AHEAD OF THE FRONT TO 10-15 KNOTS. THE FRONT SHOULD CROSS THE WATERS EARLY SATURDAY WITH A NORTHWEST FLOW OF 10-15 KNOTS ENSUING. SIGNIFICANT SEAS WILL BE 1-3 FEET THURSDAY AND MOST OF THE DAY FRIDAY. SATURDAY THE RANGE WILL INCREASE TO 2-4 FEET WITH THE HIGHER SEAS ACROSS THE OUTER WATERS.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ NEAR TERM...DCH SHORT TERM...TRA LONG TERM...SHK AVIATION...BJR/SRP

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