Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 171732 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 132 PM EDT WED SEP 17 2014 .SYNOPSIS... HIGH PRESSURE WILL EXTEND DOWN INTO THE CAROLINAS FROM THE NORTH PROVIDING FALL-LIKE WEATHER FOR THE REMAINDER OF THE WEEK. THE NEXT COLD FRONT WILL MOVE THROUGH BY MONDAY NIGHT. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1100 AM WEDNESDAY...A COLD FRONT HAS PUSHED OFFSHORE AND WE ARE NOW UNDER THE INFLUENCE OF COOLER/DRIER AIR...ESPECIALLY ALOFT. AREAS OF LOW CLOUDS HAVE DELAYED HEATING IN SOME LOCATIONS AND RESULTED IN DIFFERENTIAL HEATING BOUNDARIES. HOWEVER...THESE LOW CLOUDS ARE TRANSITORY. WE EXPECT CUMULUS TO BEGIN BUILDING AROUND MIDDAY/EARLY AFTERNOON WITH STILL A GOOD SUPPLY OF MOISTURE BETWEEN 2-12 KFT. ABOVE AND BELOW THIS LEVEL...THE COLUMN IS MUCH DRIER. THIS WOULD SUGGEST THAT CONVECTION THAT DOES DEVELOP WILL HAVE A DIFFICULT TIME BUILDING TO A SIGNIFICANT DEPTH. HOWEVER...IT ALSO IMPLIES THAT STRONG SHOWERS/THUNDERSTORMS WILL HAVE THE POTENTIAL FOR STRONG/GUSTY WINDS. THIS IS REFLECTED IN THE HIGH DOWNDRAFT CAPE VALUES ACROSS THE AREA THIS AFTERNOON. ALSO...LOW WET BULB ZEROS AND LOW 50 DBZ CORE THRESHOLDS SUGGEST A POTENTIAL FOR HAIL IN THUNDERSTORMS THAT ARE ABLE TO ATTAIN ADEQUATE HEIGHT. GIVEN THERE WILL BE SOME ADDED LIFT AS AN EMBEDDED SHORTWAVE REACHES THE AREA IN NW FLOW NEAR PEAK HEATING...HAVE INCREASED POPS TO NEAR 40 PERCENT THROUGHOUT. AS HEATING DIMINISHES THIS EVE...SO SHOULD THE CONVECTION. WILL SHOW POPS DECREASING FROM W TO E TONIGHT...LASTLY ALONG THE COAST...AS THE AIRMASS STABILIZES AND UPPER LEVEL SUPPORT WANES. FOG/STRATUS MAY AGAIN FILL IN OVERNIGHT AND THU MORNING AS A STRENGTHENING SUBSIDENCE INVERSION TRAPS MOISTURE BELOW 1 KFT. MODEL SOUNDINGS SHOW THE INVERSION WILL BE MOST PRONOUNCED INLAND. ALTHOUGH SLIGHTLY COOLER AIR WILL BE WORKING INTO THE AREA...THIS WILL BE OFFSET BY PARTIAL SUNSHINE AND WE EXPECT WIDESPREAD LOWER TO MID 80S THIS AFTERNOON. LOWS TONIGHT SHOULD BE SIMILAR TO LAST NIGHT IF NOT A DEGREE OR TWO COOLER...ESPECIALLY ALONG THE COAST. WILL FORECAST LOWS IN THE MID 60S WITH SEVERAL INLAND COMMUNITIES DROPPING INTO THE LOWER 60S WHILE SEVERAL BEACH COMMUNITIES ONLY DROP INTO THE UPPER 60S TO NEAR 70. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... AS OF 300 AM WEDNESDAY...SURFACE HIGH OVER THE GREAT LAKES THU WILL SHIFT EAST TO NEW ENGLAND FRI...SETTING UP A CLASSIC WEDGE. LIGHT NORTHEAST FLOW THU AND LIMITED LOW LEVEL MOISTURE MAY ALLOW FOR SOME SUNSHINE BUT INCREASED NORTHEAST FLOW AND LOW LEVEL MOISTURE FRI WILL LIKELY LEAD TO AN INCREASE IN CLOUD COVER. PRECIP CHANCES ARE RATHER LIMITED EACH DAY WITH WEAK SUBSIDENCE ALOFT KEEPING THE MID LEVELS DRY. THE ONLY REAL THREAT APPEARS TO BE ALONG THE IMMEDIATE COAST WHERE LOW LEVEL MOISTURE IS HIGHEST...ESPECIALLY FRI...AND SOME LIGHT RAIN COULD DEVELOP. MEASURABLE RAINFALL WILL BE DIFFICULT TO COME BY EVEN IF LIGHT RAIN DEVELOPS SO PLAN TO CONTINUE CARRYING SLIGHT CHC/LOW CHC ALONG THE COAST WITH POP AROUND 10 INLAND. NORTHEAST FLOW WILL HELP KEEP HIGH TEMPERATURES ALONG THE COAST A LITTLE BELOW CLIMO THROUGH THE PERIOD. FARTHER INLAND HIGHS WILL BE NEAR CLIMO WITH A LITTLE MORE SUN AND A LITTLE LESS MARINE INFLUENCE. LOW TEMPERATURES WILL END UP A LITTLE ABOVE CLIMO DUE TO CLOUDS AND BOUNDARY LAYER MIXING. && .LONG TERM /SATURDAY THROUGH TUESDAY/... AS OF 300 AM WEDNESDAY...HIGH PRESSURE WEDGE IN PLACE AT THE START OF THE PERIOD WILL HOLD ON INTO AT LEAST THE SECOND HALF OF THE WEEKEND...KEEPING TEMPERATURES IN MOST AREAS A LITTLE BELOW CLIMO. GUIDANCE IS SHOWING HINTS THE WEDGE COULD HOLD ON INTO MON GIVEN THE LACK OF SURFACE AND MID LEVEL FEATURES. THIS WOULD MAINTAIN LOW CLOUDS AND LIGHT PRECIP...MAINLY ALONG THE COAST...INTO NEXT WEEK. FARTHER INLAND THERE IS LIKELY TO BE A NARROW GRADIENT BETWEEN MOSTLY CLOUDY AND MOSTLY SUNNY. THIS IS COMPLICATED SOMEWHAT BY POTENTIAL WEAK LOW PRESSURE DEVELOPING ALONG THE FRONT STALLED OFFSHORE. THIS FEATURE COULD ENHANCE THE WEDGE AS IT MOVES UP THE COAST BEFORE HELPING TO BREAK THE WEDGE AS IT EXITS NORTHEAST. HOWEVER ITS INFLUENCE ON THE AREA REMAINS IN QUESTION WITH MANY OF THE MEDIUM RANGE SOLUTIONS KEEPING THIS FEATURE ON THE WEAK SIDE AND FARTHER OFF THE COAST. COLD FRONT APPROACHES FROM THE NORTHWEST MON...DRIVEN SOUTH BY STRONG MID LEVEL TROUGH DIVING SOUTH ACROSS THE GREAT LAKES AND CANADIAN HIGH PRESSURE. FROPA DURING THE DAY MON WILL HAVE SOME DIURNAL INSTABILITY TO WORK WITH...BUT HOW MUCH REMAINS A QUESTION. EXPECT CONVECTION AHEAD OF THE FRONT BUT STRENGTH AND COVERAGE WILL PARTLY DEPEND ON TIMING. FRONT STALLS OFFSHORE MON NIGHT INTO TUE...SIMILAR TO THIS WEEKS COLD FRONT AS SURFACE HIGH BUILDS IN FROM THE GREAT LAKES. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... AS OF 18Z...TERMINALS ARE VFR THIS AFTERNOON EXCEPT FOR MVFR CIGS AT KLBT. AN UPPER IMPULSE WILL MOVE THROUGH LATE DAY COUPLED WITH PEAK HEATING. ISOLATED/SCATTERED CONVECTION WILL DEVELOP...WITH MODERATE CONFIDENCE KILM WILL EXPERIENCE A THUNDERSTORM BY 21Z. PRECIPITATION SHOULD GRADUALLY DIMINISH THIS EVENING. BY MIDNIGHT IFR/LIFR STRATUS/VSBYS WILL BE AN INCREASING CONCERN. ALL MOS GUIDANCE INDICATES IFR/LIFR CONDITIONS. CONFIDENCE IS HIGH MVFR CONDITIONS WILL DEVELOP. CONFIDENCE MODERATE TO HIGH LIFR CONDITIONS WILL DEVELOP WITH LOWEST CONFIDENCE AT KLBT. CIGS RISE TO MVFR BY MID-MORNING. EXTENDED OUTLOOK...GUSTY NORTHEAST WINDS EXPECTED FRI/SAT AS THE COOL AIR WEDGE STRENGTHENS OVER THE CAROLINAS. VFR ON SUNDAY. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 1100 AM WEDNESDAY...NE WINDS WILL REMAIN THROUGH THE PERIOD...BUT SPEEDS WILL CONTINUE TO BE 10 KT OR LESS AS THE GRADIENT REMAINS SLACK. EASTERLY SWELL FROM DISTANT EDOUARD WILL ALLOW SEAS TO BE CONSIDERABLY HIGHER THAN THE WIND SPEEDS WOULD OTHERWISE INDICATE. SEAS OF 3 TO 4 FT WILL BE COMMON WITH SOME 5 FT SEAS ACROSS THE OUTERMOST WATERS. THE SWELL PERIOD WILL BE ON THE ORDER OF 13 TO 15 SECONDS. SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... AS OF 300 AM WEDNESDAY...LIGHT NORTHEAST FLOW ON THU WILL INCREASE SIGNIFICANTLY FRI AS HIGH PRESSURE BUILDS DOWN THE COAST AND GRADIENT BECOMES PINCHED. THU NORTHEAST FLOW WILL BE IN THE REALM OF 10 KT BUT BY MIDDAY FRI SOLID 20 KT WITH HIGHER GUSTS IS EXPECTED. SEAS 2 TO 4 FT THU FLIRTS WITH HEADLINE CRITERIA FRI...ESPECIALLY NORTH OF CAPE FEAR...BUILDING TO 4 TO 5 FT WITH POTENTIAL FOR 6 FT ACROSS PARTS OF NC WATERS. LONG TERM /SATURDAY THROUGH SUNDAY/... AS OF 300 AM WEDNESDAY...ELEVATED NORTHEAST FLOW CONTINUES SAT AS HIGH PRESSURE RIDGES DOWN THE COAST. GRADIENT WILL MAINTAIN 15 TO 20 KT WINDS SAT BUT WEAKENING GRADIENT SUN WILL ALLOW FOR A REDUCTION IN SPEEDS. WEAK LOW PRESSURE PASSES EAST OF THE WATERS SUN. IN THE WAKE OF THIS LOW SUN NIGHT LIGHT SOUTHWEST FLOW WILL DEVELOP. SEAS 3 TO 5 FT WITH OCCASIONAL 6 FT POSSIBLE SAT DECREASE TO 2 TO 4 FT SUN. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ NEAR TERM...RJD SHORT TERM...III LONG TERM...III AVIATION...MRR/RJD

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