Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 010544 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 144 AM EDT TUE SEP 1 2015 .SYNOPSIS...
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LOW PRESSURE ALONG THE NORTH CAROLINA COAST SHOULD MOVE NORTHEAST AND AWAY FROM THE AREA OVERNIGHT. A LINGERING TROUGH WILL REMAIN ACROSS THE EASTERN CAROLINAS ON TUESDAY. HIGH PRESSURE WILL BUILD INTO THE AREA FROM THE NORTH FRIDAY NIGHT AND THROUGH THE WEEKEND.
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&& .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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AS OF 130 AM TUESDAY...NO CHANGES TO THE FORECAST WITH THE LATEST UPDATE. PREVIOUS DISCUSSION FOLLOWS: INLAND SHOWERS HAVE DISSIPATED BUT ISOLATED ACTIVITY CONTINUES OFFSHORE...MOVING EASTWARD. BASED ON SURFACE WIND DIRECTIONS AT BUOYS AND MESONET SITES THE LOW APPEARS TO HAVE MOVED TO A POSITION 10-15 MILES EAST OF TOPSAIL ISLAND. THE LATEST RUC MODEL ISN`T BAD AND WAS BLENDED INTO OUR WIND GRIDDED DATASET FOR THE REMAINDER OF THE NIGHT. LOW CLOUDS HAVE DEVELOPED A FEW HOURS MORE QUICKLY THAN ANTICIPATED. CLOUDINESS CURRENTLY EXTENDING FROM ELIZABETHTOWN TO WHITEVILLE SHOULD GRADUALLY EXPAND AFTER MIDNIGHT TO COVER MOST OF SE NORTH CAROLINA AND SOME PARTS OF NE SOUTH CAROLINA AS WELL. DISCUSSION FROM 730 PM FOLLOWS... THE DEEP TROPICAL MOISTURE CHANNEL IS FINALLY BEGINNING TO SHIFT OFFSHORE. WATER VAPOR IMAGERY SHOWS THE LEADING/EASTERN EDGE OF THE DRY AIR NOW ON THE NORTH CAROLINA COAST. LOCALLY HEAVY RAIN CONTINUES TO FALL HOWEVER AS SURFACE LOW PRESSURE AND ITS ASSOCIATED MAXIMUM IN LOW-LEVEL CONVERGENCE IS CENTERED JUST EAST OF CAPE FEAR. THE 12/18Z MODELS WERE QUITE POOR WITH THE ACCURACY OF THE POSITION OF THIS LOW. OF ALL THE MODELS AVAILABLE TO US ONLY THE 12Z WRF-NMM AND 12Z WRF-ARW SHOWED THE LOW IN THE PROPER POSITION AT 21Z. THESE TWO MODELS ARE THE BASIS FOR THE UPDATED FORECAST THIS EVENING. THE LOW SHOULD MOVE NORTHEASTWARD THIS EVENING AND AWAY FROM SOUTHEASTERN NORTH CAROLINA. RAINFALL SHOULD SLOWLY TAPER OFF OVER THE NEXT 2-3 HOURS...LINGERING FOR COASTAL PENDER COUNTY AND THE ADJACENT OCEAN WATERS THE LONGEST. AN ADDITIONAL ONE-HALF INCH TO ONE INCH OF RAIN COULD POTENTIALLY FALL FROM WRIGHTSVILLE BEACH TO TOPSAIL ISLAND OVER THE NEXT FEW HOURS. ONCE THE PRECIP CLEARS THE COAST...CLEAR SKIES ADVANCING IN FROM THE WEST SHOULD OVERSPREAD MOST OF THE AREA. HOWEVER...MODELS ARE INDICATING WRAP-AROUND MOISTURE WILL RE-ENTER THE PICTURE FROM THE NORTH...SPREADING A DECK OF LOW STRATUS INTO AT LEAST SOUTHEASTERN NORTH CAROLINA AFTER MIDNIGHT. WHERE THESE LOW CLOUDS DO NOT REACH...BETTER RADIATIONAL COOLING CONDITIONS WILL INTERSECT WITH LINGERING SURFACE MOISTURE AND WE CAN EXPECT AREAS OF FOG TO DEVELOP. MOS GUIDANCE IS INDICATING THIS FOG COULD BECOME LOCALLY DENSE...PARTICULARLY ACROSS SOUTH CAROLINA`S PEE DEE REGION.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH WEDNESDAY NIGHT/... AS OF 300 PM MONDAY...PROGRESSIVE PATTERN THROUGH THE PERIOD. A TROUGH OF LOW PRESSURE WILL BE ALIGNED RIGHT ALONG THE COAST TUE. A MID-LEVEL VORTICITY MAXIMA ASSOCIATED WITH FORMER TROPICAL STORM ERIKA WILL BE MOVING UP THE SOUTHEAST COAST. THIS FEATURE WILL BE APPROACHING THE FORECAST AREA TUE NIGHT AND IS EXPECTED TO MOVE OFF THE CAROLINA COAST DURING THE DAY WED. A RIDGE BUILDING ACROSS THE MIDDLE OF THE COUNTRY NEAR THE END OF THE PERIOD WILL ALLOW A NW FLOW TO DEVELOP ACROSS THE CAROLINAS. A WEAK SHORTWAVE EMBEDDED IN THE FLOW IS FORECAST TO APPROACH LATE WED NIGHT. THERE WILL BE A GOOD AMOUNT OF DRY AIR MOVING ACROSS THE AREA AND THIS IN AND OF ITSELF WILL BE GOOD REASON TO KEEP THE POPS IN SLIGHT CHANCE/CHANCE CATEGORY. WILL SHOW HIGHEST POPS ALONG THE COAST AHEAD OF AFOREMENTIONED MID-LEVEL VORTICITY...LATE TUE NIGHT AND WED MORNING. HOWEVER...IT MAY END UP THAT MOST OF THE PRECIPITATION AND CERTAINLY THE HEAVIEST OF THE SHOWER AND THUNDERSTORM ACTIVITY...WILL BE OFFSHORE. WILL ALSO TRY TO CAPTURE THE SLIGHT UPTICK IN THE POTENTIAL FOR CONVECTION WED NIGHT WITH THE MID-LEVEL SHORTWAVE. TEMPERATURES WILL RETURN TO SLIGHTLY ABOVE SEASONABLE LEVELS FOR EARLY SEPTEMBER. && .LONG TERM /THURSDAY THROUGH MONDAY/... AS OF 300 PM MONDAY...THURSDAY SHOULD BE THE FIRST FULL DAY WHERE THE AREA IS NO LONGER DEALING WITH ANY REMNANTS OF ERIKA. PW DROPS TO ABOUT 1.6 INCHES ACROSS MUCH OF THE AREA BUT THERE WILL BE A MID LEVEL DISTURBANCE MOVING THROUGH IN NORTHWEST FLOW. GFS NOW SHOWS A VERY WEAK ATTENDANT SURFACE FEATURE AND SO FEEL THAT THE LOW END SCATTERED (30 POPS) THAT WE HAVE IN THE FORECAST IS JUST FINE. QPF PROSPECTS WILL BE LOW DUE TO THE LOWER AVAILABLE MOISTURE AND WEAK FORCING. ANOTHER MID LEVEL FEATURE CROSSES ON FRIDAY BUT IN MORE OF WESTERLY RATHER THAN NORTHWESTERLY SOURCE WHICH MAY FAVOR BETTER RAIN CHANCES DUE TO DEEPER MOISTURE AT LEAST ACCORDING TO ECMWF. GFS HAS MORE OF A REPEAT OF THURSDAY. LARGE UPPER RIDGE BUILDS OVER THE EASTERN U.S. AND MID-ATLANTIC OVER THE WEEKEND WITH ITS CENTER WELL TO OUR NORTH. THE SAME WILL HOLD TRUE AT THE SURFACE. THIS WILL BRING A DEEP EASTERLY FLOW TO THE AREA THAT OFTEN LEADS TO TROPICAL BLUE SKIES LADEN WITH TOWERING CU AND ALSO A FEW STRAY SHOWERS MAINLY ALONG THE COAST. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/...
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AS OF 06Z...A MIXTURE OF VFR/MVFR/IFR ON TAP OVERNIGHT WELL INTO THE EARLY MORNING HOURS AS AREAS OF FOG AND LOW CIGS DEVELOP. CONDITIONS IMPROVE TO VFR LATE TUESDAY MORNING AND CONTINUE THROUGH THE END OF THE VALID TAF PERIOD. SOME OBSERVATIONS ARE BEGINNING TO SHOW FEW/SCT LOW CIGS MOVING ACROSS PORTIONS OF THE AREA...BUT OVERALL SKIES ARE CLEAR AND WINDS ARE LIGHT. GUIDANCE CONTINUES TO INDICATE INCREASING MOISTURE OVERNIGHT AND AS A RESULT ANTICIPATE STRATUS AND FOG DEVELOPMENT TO CREATE MVFR/IFR CONDITIONS. CONFIDENCE REMAINS LOW REGARDING WHICH FEATURE WILL PREVAIL...THUS HAVE KEPT A MIXTURE IN GOING FORECAST ATTM. ON TUESDAY...CONDITIONS WILL IMPROVE TO VFR WITH LIGHT WINDS BECOMING SOUTHEAST AOB 10 KTS IN THE AFTERNOON. CANNOT ENTIRELY RULE OUT AN ISOLATED SHRA/TSRA IN THE AFTERNOON HOURS. TOWARDS THE EVENING HOURS...EXPECT VFR TO PREVAIL WITH WINDS BECOMING LIGHT. EXTENDED OUTLOOK...PREDOMINATELY VFR WITH BRIEF MORNING FOG AND ISOLATED/SCATTERED AFTERNOON CONVECTION.
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&& .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 130 AM TUESDAY...NO CHANGES TO THE FORECAST WITH THE LATEST UPDATE. PREVIOUS DISCUSSION FOLLOWS: OBSERVATIONS SUGGEST THE LOW IS CURRENTLY LOCATED 10-15 MILES EAST OF TOPSAIL ISLAND AND MOVING NORTHEASTWARD. ISOLATED SHOWERS CONTINUE ACROSS THE NC COASTAL WATERS BUT SHOULD END OVER THE NEXT FEW HOURS. A BELT OF STRONGER SOUTH-SOUTHWEST WINDS OFFSHORE AHEAD OF THE LOW HAS BUILT SEA HEIGHTS AT THE FRYING PAN SHOALS BUOY TO 5 FEET...WITH BUOYS CLOSE TO THE COAST STILL REPORTING 3-4 FEET. DISCUSSION FROM 730 PM FOLLOWS... USING RADAR IMAGERY AND SURFACE OBSERVATIONS LOW PRESSURE IS CENTERED JUST EAST OF CAPE FEAR AT 7 PM. OF ALL THE MODELS AVAILABLE TO US THE TWO THAT SEEM TO HAVE THE BEST HANDLE ON THE CURRENT POSITION AND MOVEMENT OF THIS FEATURE ARE THE 12Z WRF-NMM AND 12Z WRF-ARW. THESE MODELS ARE THE BASIS FOR THIS EVENING UPDATE. OFFSHORE WINDS SHOULD GRADUALLY DIMINISH THROUGH THE NIGHT SOUTH OF CAPE FEAR...BUT NORTH OF CAPE FEAR WE`VE GOT A FEW MORE HOURS OF INTERESTING WEATHER AS SWIRLING WINDS UP TO 20 KNOTS AND WIDESPREAD SHOWERS WITH HEAVY RAINFALL WILL CONTINUE. SEAS HAVE BUILT TO A SOLID 4 FEET NEAR AND NORTH OF CAPE FEAR AND THERE SHOULD BE SOME 5-FOOTERS DEVELOPING SHORTLY ACCORDING TO OUR LOCAL WAVE MODEL USING UPDATED WIND FORECASTS. AN EXERCISE CAUTION HEADLINE HAS BEEN HOISTED NORTH OF CAPE FEAR. AFTER MIDNIGHT SEAS SHOULD SUBSIDE THROUGHOUT THE REGION TO 2-3 FEET. SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... AS OF 300 PM MONDAY...A SLACK PRESSURE GRADIENT IS EXPECTED TO BE IN PLACE THROUGH THE PERIOD AND THIS SHOULD KEEP WIND SPEEDS TO 10 KT OR LESS. SW TO S WINDS DURING THE AFTERNOON AND EVE BOTH DAYS SHOULD BECOME MORE OFFSHORE OVERNIGHT AND DURING THE MORNING DUE TO A LAND BREEZE MOVING OFFSHORE. SEAS WILL BE MAINLY 2 FT...BUT UP TO 3 FT TUE. A WEAK 8 TO 10 SECOND SE SWELL WILL PERSIST. LONG TERM /THURSDAY THROUGH SATURDAY/... AS OF 300 PM MONDAY...WIND SPEEDS WILL BE CAPPED AT JUST 10 KNOTS THROUGH MOST OF IF NOT THE ENTIRE PERIOD. IT MAY STRUGGLE THURSDAY AND FRIDAY TO FIND AN ESTABLISHED DIRECTION HOWEVER THOUGH NORTH AND EAST COMPONENTS WILL TEND TO BE FAVORED. THIS WILL BE FORTIFIED FRIDAY NIGHT INTO SATURDAY AS A STRONGER HIGH GETS ESTABLISHED ACROSS NORTHEASTERN U.S. BETWEEN THE LENGTHENING SPATIAL AND TEMPORAL FETCH ON SATURDAY THE WAVE FORECAST MAY RISE FROM 2 TO 2-3 FT.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ SYNOPSIS...RJD NEAR TERM...REK/TRA SHORT TERM...RJD LONG TERM...MBB AVIATION...SGL MARINE...REK/RJD/TRA/MBB

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