Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 281115 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 715 AM EDT FRI AUG 28 2015 .SYNOPSIS... A WEAK FRONT WILL MEANDER OFF THE THE COAST AS HIGH PRESSURE SLOWLY BUILDS INTO THE CAROLINAS OVER THE WEEKEND. ERIKA IS EXPECTED TO APPROACH THE BAHAMAS AND SOUTH FLORIDA LATE IN THE WEEKEND TRACKING THROUGH FLORIDA INTO EARLY NEXT WEEK...AND POSSIBLY REMAINING ON A MORE WESTWARD TRACK CLOSER TO THE GULF COAST. && .NEAR TERM /THROUGH TONIGHT/... AS OF 650 AM FRIDAY...HAVE STAYED WITH A DRIER BIAS FOR THIS NEAR TERM FORECAST...AND KEPT THE THREAT FOR LOW CHANCE POPS ACROSS THE COASTAL COUNTIES WITH DIURNALLY DRIVEN CONVECTION THE MAIN EMPHASIS FROM LATE THIS MORNING THRU EARLY THIS EVENING. LATEST WATER VAPOR IMAGERY INDICATES A MUCH DRIER PICTURE COMPARED THIS TIME YESTERDAY MORNING. PROGGED MODEL SOUNDINGS INDICATE DRY AIR BETWEEN 350 MB AND 900 MB BECOMING MORE DOMINANT ACROSS THE FA LATER THIS MORNING THRU TONIGHT AND INTO THE SHORT TERM PERIOD. THE SOMEWHAT STALLED SFC BOUNDARY ORIENTED NE-SW AND PARALLEL TO THE ILM CWA COASTLINE...WILL DRIFT SLIGHTLY FURTHER OFFSHORE THIS PERIOD. THIS HAS ALREADY ALLOWED THE MODEST 1020+ SFC HIGH BROADLY CENTERED OVER THE NE STATES AND MID-ATLANTIC TO RIDGE OR NOSE SOUTH-SOUTHWESTWARD PUSHING DRIER AIR AND LOWER SFC DEWPOINTS TO AND ACROSS THE ILM CWA. ALREADY OBSERVING WIDESPREAD 60S DEWPOINTS ACROSS THE FA...ALL THE WAY TO THE IMMEDIATE COAST. MODELS INDICATE POSSIBLY AROUND 60 THIS AFTN ACROSS THE NORTHERNMOST PORTIONS OF THE FA THIS AFTN WHERE MIXING OF DRIER AIR ALOFT TO THE SFC MAY OCCUR. WITH ALL THIS SAID...THE BEST FORCING/LIFT FOR CONVECTION WILL INITIALLY START JUST ALONG AND OFF THE IMMEDIATE COAST...AND SWITCH FURTHER EAST AND FURTHER OFF THE MAINLAND AS THE BOUNDARY LAYER ASSOCIATED WITH THE STALLED SFC FRONT DRIFTS EASTWARD. HAVE ALSO GONE WITH OVERALL LESS CLOUD COVERAGE...ESPECIALLY TONIGHT WHERE ANY DEBRIS CONVECTIVE CLOUDS WILL EITHER STAY WITHIN THE MEAN FLOW OVER THE ATL WATERS...OR THE DEBRIS CLOUDS THAT PUSH N-NE FROM GA WILL SCOUR OUT A GOOD DEAL PRIOR TO PUSHING ACROSS THE FA. AS FOR TEMPS...LOOKING AT WIDESPREAD 80S FOR MAX TEMPS TODAY...AND WIDESPREAD 60S FOR MINS EXCEPT NEAR 70 ALONG THE IMMEDIATE COAST AND EXTREME SOUTHERN PORTIONS OF THE FA. STAYED WITH A SLIGHTLY COOLER BIAS FOR TONIGHTS MINS USING THE LATEST AVBL MODEL MOS GUIDANCE. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... AS OF 330 AM FRIDAY...DRY AIR CONTINUES TO FUNNEL INTO THE AREA IN NORTHERLY FLOW ON BACK END OF LINGERING FRONT/TROUGH/OFF SHORE ON SAT. A WAVE OF LOW PRESSURE DEVELOPS ALONG THE FRONT AND LIFTS OFF TO THE NORTHEAST THROUGH LATE SAT INTO SUN LEAVING WEAK HIGH PRESSURE OVER THE AREA THROUGH SUN NIGHT. THE NORTHERLY FLOW BETWEEN HIGH PRESSURE INLAND AND LOW OFF SHORE ON SAT WILL BEGIN TO VEER AROUND BECOMING MORE ON SHORE THROUGH SUNDAY. ABOVE THE SURFACE...LOW PRESSURE ALOFT OVER THE CENTRAL GULF COAST WILL BEGIN TO MOVE SLOWLY NORTHEAST AND WEAKEN PROVIDING A STEADY SOUTHERLY FLOW OF MOISTURE INTO THE CAROLINAS IN THE LOW TO MID LEVELS SAT NIGHT INTO SUNDAY. THIS IS DEPICTED WELL BY THE MOISTURE PROFILES AND GUIDANCE SHOWING A DEEPENING OF MOISTURE THROUGH THE COLUMN AND AN INCREASE IN CLOUD COVER ON SUNDAY. WITH SUCH DRY AIR IN PLACE IN THE BEGINNING OF PERIOD...EXPECT LIMITED TO NO SHWR ACTIVITY WITH A FEW SHWRS/TSTMS POSSIBLE IN LOCALIZED CONVERGENCE MAINLY ASSOCIATED WITH THE SEA BREEZE OVER THE WEEKEND...WITH MAINLY SOME HIGHER LEVEL CLOUDS AROUND. PCP WATER VALUES DOWN LESS THAN AN INCH OVER INLAND NORTH CAROLINA INCREASE UP TO 1.25 INCHES BY SAT EVE AND UP CLOSE TO 1.5 TO 1.75 INCHES BY SUN AFTN IN A SLOW INCREASE IN MAINLY UPPER LEVEL MOISTURE. THEREFORE EXPECT BETTER CHC OF CONVECTION ON SUNDAY BUT GFS AND ECMWF BOTH SHOWING A WEAKENED ERIKA REACHING OVER SOUTHEAST FLORIDA COAST SUN NIGHT INTO MON WITH EASTERLY FETCH OF MOISTURE REACHING AS FAR NORTH AS SOUTH CAROLINA. OVERALL WESTWARD ADJUSTMENT BY NHC AND GUIDANCE IS EVEN FARTHER WEST. MUCH UNCERTAINTY STILL EXISTS WITH TRACK AND INTENSITY AND THEREFORE WILL NEED TO ADJUST IN FUTURE FORECASTS. && .LONG TERM /MONDAY THROUGH THURSDAY/... AS OF 330 AM FRIDAY...TRENDING DRIER IN OVERALL FORECAST AS LATEST MODEL RUNS SHOW ERIKA OVER FLORIDA ON MONDAY AND THEN TAKING A TURN IN GEORGIA OR POSSIBLY TRACKING ACROSS FLORIDA TOWARD THE GULF COAST. THIS WOULD PRODUCE A GREATER EXTENDED EAST TO NORTHEASTERLY FETCH OVER THE CAROLINAS. FOR NOW KEPT WITH LOWER END CHC POPS AND WITH GREATEST IMPACTS FROM ERIKA STILL EXPECTED MID WEEK...WED INTO THURS. IF ERIKA DOES TAKE A TRACK TO OUR SOUTH MAY END UP WITH MORE IN THE WAY OF SOME GUSTY ON SHORE WINDS AND EXTENDED SWELL ENERGY PRODUCING SOME COASTAL IMPACTS BUT WITH SUCH UNCERTAINTY IN THE MODELS IT IS STILL DIFFICULT TO SAY WITH ANY CERTAINTY. LATEST GFS KEEPS PCP WATER VALUES LOWER THAN 1.5 INCHES THROUGH MOST OF PERIOD OVER NC WITH VALUES REACHING UP CLOSE TO 2 INCHES ON NORTHERN STRETCH OF ERIKA INTO SOUTH CAROLINA. UPPER RIDGE BUILDING OVER THE EASTERN CONUS WILL LEAVE A WEAKNESS BUT TRACK WILL ALSO BE DEPENDENT ON STRENGTH OF ERIKA AS SHE MAKES HER WEST NORTHWEST. THE GFS WANTS TO PULL ERIKA TOWARD THE WEST GETTING PULLED BY THE MID TO UPPER LOW OVER THE WESTERN GULF. OVERALL WENT A BIT MORE OPTIMISTIC FOR OUR AREA WITH A BIT LESS CLOUD COVER AND LESS WIDESPREAD CONVECTION. RAISED MAX TEMPS A BIT...EXPECTING MID TO UPPER 80S MOST PLACES WITH LOWS IN THE LOW TO MID 70S. && .AVIATION /12Z FRIDAY THROUGH TUESDAY/... AS OF 06Z...POTENTIAL PERSISTS FOR AREAS OF MVFR/IFR DUE TO STRATUS AND FOG DEVELOPMENT LATE OVERNIGHT INTO THE EARLY MORNING HOURS ON FRIDAY. OTHERWISE EXPECT VFR WITH VCSH/VCTS THROUGHOUT THE PERIOD. A FRONTAL SYSTEM REMAINS JUST OFFSHORE WITH RADAR IMAGERY DEPICTING SCATTERED SHOWERS ACROSS THE OFFSHORE WATERS. LATEST GUIDANCE CONTINUES TO DEPICT POTENTIAL FOR THE DEVELOPMENT OF PATCHY FOG AND STRATUS...WHICH COULD CREATE PERIODS OF MVFR/IFR. AFTER DAYBREAK ON FRIDAY...CONDITIONS WILL IMPROVE TO VFR AND NORTHEAST WINDS WILL INCREASE TO AOB 12 KTS...WITH OCCASIONAL HIGHER GUSTS POSSIBLE. A WIND-SHIFT TO THE EAST WILL OCCUR INTO THE AFTERNOON HOURS...WITH VCSH/VCTS POSSIBLE THROUGH THE REST OF THE PERIOD. INTO THE EVENING HOURS...ANY LINGERING ACTIVITY WILL DISSIPATE AND WINDS WILL BECOME LIGHT. EXTENDED OUTLOOK...PREDOMINATELY VFR WITH ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS THROUGH THE EXTENDED. BRIEF MORNING FOG/STRATUS IS ALSO EXPECTED EACH DAY. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 650 AM FRIDAY...THE ENTIRE ILM COASTAL WATERS SHOULD NOW BE ENCOMPASSED WITH A STEADY AND MODEST NE WIND. THE SFC PG FROM THE RIDGING FROM THE 1020+ HIGH FROM THE NORTH WILL BE TIGHT ENOUGH TO PRODUCE A SOLID 15 KT SUSTAINED WIND...EXCEPT INITIALLY 15 TO 20 KT ACROSS THE ILM NC WATERS. LOOKING AT KLTX VWP AND ADJACENT 88D VWPS...WINDS 1K TO 2K FT OFF THE DECK ARE RUNNING NE-ENE AT 15 TO 30 KT. WITH SOME OF THIS MIXING DOWN TO THE OCEAN SFC AS 20+ WIND GUSTS. LOOK FOR A SOLID 15 KT NE WIND SPEED TONIGHT FOR ALL WATERS...WIND DIRECTIONS MAY BRIEFLY VEER TO THE ENE-E NEAR SHORE THIS AFTN/EARLY EVENING DUE TO A RESULTANT WIND BOUNDARY. SIGNIFICANT SEAS WILL RUN A SOLID 4 FT FOR THE ILM NC WATERS FROM CAPE FEAR NORTHWARD THRU THE PERIOD...AND 2 TO 4 FT SOUTH OF THE CAPE. THE 4 TO 6 SECOND PERIOD WIND WAVES WILL DOMINATE THE SIGNIFICANT SEAS...WITH THE UNDERLYING 1 TO 1.5 FOOT ESE GROUND SWELL AT 11-12 SECOND PERIODS REMAINING VISUALLY PRESENT. THE SCATTERED CONVECTION COVERAGE ASSOCIATED WITH THE SOMEWHAT STALLED SFC FRONT...WILL SWITCH TO THE ADJACENT OFFSHORE WATERS. SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... AS OF 330 AM FRIDAY...NORTHEAST WINDS ON SATURDAY BETWEEN HIGH PRESSURE EXTENDING DOWN OVER THE CAROLINAS AND WEAK LOW PRESSURE DEVELOPING ALONG LINGERING BOUNDARY OFF SHORE. AS THIS LOW PULLS AWAY THROUGH SUNDAY...WINDS MAY COME AROUND TO A MORE EASTERLY ON SHORE DIRECTION AROUND HIGH PRESSURE. EXPECT DEEPEST MOISTURE AND CONVECTION MAINLY EAST OF WATERS ASSOCIATED WITH LINGERING BOUNDARY AND WAVE OF LOW PRESSURE ALONG IT. LATEST FORECAST TRACKS WEAKENED ERIKA OVER FLORIDA BY SUNDAY NIGHT INTO EARLY MONDAY. THIS WOULD MAINLY PRODUCE EASTERLY SWELL ENERGY REACHING INTO THE LOCAL WATERS OVER THE WEEKEND WITH SEAS BASICALLY REMAINING 2 TO 4 FT MOST WATERS. LONG TERM /MONDAY THROUGH TUESDAY/... AS OF 330 AM FRIDAY...LATEST FORECAST TRACKS ERIKA OVER FLORIDA AND KEEPS TRENDING WESTWARD WITH TIME GETTING PULLED BY MID TO UPPER LOW IN THE WESTERN GULF. MAY SEE WINDS REMAIN E-NE ONLY RISING UP TO 15 KTS. WITH SO MUCH UNCERTAINTY IN MODEL RUNS...WILL NEED TO KEEP AN EYE ON EVOLUTION OF ERIKA. FOR NOW WILL KEEP MAINLY EAST WINDS LESS THAN 15 KTS AND SEAS BASICALLY 2 TO 4 FT WITH A DIMINISHING LONGER PERIOD SWELL. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ SYNOPSIS...RGZ NEAR TERM...DCH SHORT TERM...RGZ LONG TERM...RGZ AVIATION...DCH/SGL

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