Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 170220 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 920 PM EST TUE DEC 16 2014 .SYNOPSIS... SHOWERS WILL MOVE OFFSHORE TONIGHT AS A COLD FRONT CROSSES THE COAST. SEASONABLY COOL AND FAIR WEATHER WILL FOLLOW WEDNESDAY THROUGH FRIDAY. AN APPROACHING STORM SYSTEM COULD BRING WET WEATHER DURING THE UPCOMING WEEKEND. A DRYING TREND IS EXPECTED EARLY NEXT WEEK WITH SEASONABLE TEMPERATURES...AS HIGH PRESSURE FROM THE UPPER MID-WEST DROPS SOUTHEAST INTO THE CAROLINAS. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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AS OF 920 PM TUESDAY...THIS HAS BEEN THE LITTLE LINE OF SHOWERS THAT COULD! EVEN THE HRRR HAS NOT SHOWN THE INCREDIBLY SOLID LINE OF SHALLOW CONVECTION WE HAVE MOVING EAST ACROSS THE AREA. RAINFALL AMOUNTS HAVE BEEN LIGHT...GENERALLY UNDER A TENTH OF AN INCH. THE LUMBERTON ASOS REPORTED 0.11 AND THE LUMBERTON MESONET STATION HAD 0.14, THE TWO HIGHEST GAUGE TOTALS AVAILABLE TO US. RADAR ESTIMATES ARE UPWARDS OF HALF AN INCH ACROSS NORTHERN ROBESON COUNTY NEAR THE CUMBERLAND COUNTY LINE. CONVECTIVE ACTIVITY SHOULD CONTINUE TO ADVECT EASTWARD AND OFF THE COAST BY MIDNIGHT. IN ITS WAKE CLEAR SKIES ARE STILL EXPECTED. PREVIOUS DISCUSSION FROM 645 PM FOLLOWS... THE FIRST WAVE OF PREFRONTAL SHOWERS AND SPRINKLES HAVE DIMINISHED AND/OR MOVED EAST OF THE AREA. HOWEVER RADAR COMPOSITES SHOW A NARROW BAND OF SHOWERS DEVELOPING ALONG THE FRONT ITSELF...CURRENTLY ACROSS FAYETTEVILLE, LAURINBURG AND BENNETTSVILLE. ENVIRONMENTAL LAPSE RATES BETWEEN 850 AND 600 MB ARE ACTUALLY QUITE STEEP (NEAR 6.5 DEG/KM OR MOIST-ADIABATIC) AND THIS ACTIVITY IS CONVECTIVE IN NATURE WITH RADAR REFLECTIVITY IMPLYING THERE MAY BE A FEW MINUTES OF QUITE HEAVY RAINFALL. SPC AUTOMATED MESOANALYSIS IS SHOWING ELEVATED CAPE AROUND 100 J/KG AHEAD OF THE FRONT. MOISTURE IS A LIMITING FACTOR WITH DEWPOINTS GENERALLY IN THE 50S WITH LIMITED ATLANTIC INFLOW AND VIRTUALLY NO MOISTURE FROM THE GULF OF MEXICO. LATEST HRRR MODEL RUNS INDICATE SCATTERED SHOWERS MAINLY ACROSS SE NORTH CAROLINA CONTINUING FOR THE NEXT 2-3 HOURS...THEN SHIFTING OFFSHORE. ACTIVITY WILL BE MORE SPARSE OR ENTIRELY ABSENT ACROSS NE SOUTH CAROLINA AS THE BEST SYNOPTIC/UPPER LEVEL FORCING REMAINS NORTH. NO CHANGES HAVE BEEN MADE TO FORECAST LOW TEMPS...AROUND 40 INLAND WITH MID 40S ON THE NC BEACHES.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/... AS OF 345 PM TUESDAY...FAIR AND DRY WED/THU. SUBSIDENCE OVERWHELMS THE COLUMN ENSURING A DEEP LAYER OF LOW RH AND WEST WIND FLOW IN MID/UPPER ALTITUDES. PACIFIC ORIGIN SYSTEM AND GENERAL WEST TO EAST FLOW RESULTING IN ONLY WEAK COOL AIR ADVECTION AND MAXIMUMS WED LOOK TO REBOUND A FEW DEGREES ABOVE NORMAL FOR MID DECEMBER. A SECONDARY BUT WEAK HIGH PRESSURE SURGE MAY RESULT IN MAXIMUMS A DEGREE OR TWO COOLER THU...WITH MORE/INCREASING CIRRUS THURSDAY. && .LONG TERM /FRIDAY THROUGH TUESDAY/... AS OF 345 PM TUESDAY...LOW CONFIDENCE SPLIT FLOW FORECAST EARLY IN THE PERIOD. SURFACE HIGH PRESSURE TO BE COVERING A LARGE PAR OF THE NORTHEAST AND MID ATLANTIC ON FRIDAY. SOUTHERN BRANCH FEATURE WILL MEANWHILE BE SKIRTING THE GULF COAST. A SURPRISINGLY SLOW MOVER GIVEN THE FAIRLY ZONAL FLOW, THIS FEATURE WILL AFFECT THE AREA MOST ON SATURDAY. MODEL AGREEMENT APPEARS TO BE A LITTLE BETTER IN KEEPING THE SYSTEM TO OUR SOUTH IMPLYING THAT THIS WILL BE A LIGHT TO PERHAPS MODERATE OVERRUNNING EVENT LOCALLY. RAIN MAY LAST INTO EARLY SUNDAY BUT AS THE SYSTEM EXITS TO THE NORTHEAST (WHETHER OR NOT IN A STRENGTHENING STATE) SOME DRY AIR WILL PUSH INTO THE AREA FROM THE NW. THIS NEW AREA OF HIGH PRESSURE WILL REMAIN TO OUR NORTHWEST FOR THE REMAINDER OF THE PERIOD WHILE THE FLOW ALOFT REMAINS WEAKLY SPLIT. EARLY IN THE PERIOD DAYTIME HIGHS WILL BE A BIT SUPPRESSED BY CLOUDS AND/OR RAIN WHILE NIGHTTIME LOWS REMAIN SLIGHTLY ELEVATED ABOVE CLIMO FOR THE SAME REASON. WITH THE ARRIVAL OF THE COOLER DRY AIR DAYTIME HIGHS MAY TAKE A SMALL HIT WHILE NIGHTTIME LOWS LOSE THE BENEFIT OF CLOUDS AND RETURN TO NORMAL OR CLOSE TO IT. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... AS OF 00Z...COLD FRONT APPROACHING KFLO/KLBT. MAINLY MID LEVEL CIGS THIS EVENING BUT THERE ARE PATCHY 2.5-3.5K CIGS ALONG FRONT. SHOWERS WELL IN ADVANCE OF THE COLD FRONT ARE EXITING THE COAST NEAREST KILM...BUT A FEW ISOLATED SHOWERS ARE POPPING UP ALONG THE FRONT NW OF KLBT. THE FRONT WILL MOVE THROUGH KFLO/KLBT WITHIN THE NEXT HOUR OR TWO AND THE COASTAL TERMINALS LATER THIS EVENING. THERE IS SOME CONCERN FOR SUB-VFR VSBYS/CIGS AS WINDS DECREASE AND COOL AIR MOVES ACROSS SLIGHTLY MOIST SOILS AT KFLO/KLBT AND KCRE. THIS SHOULD MIX OUT 2-4 HOURS AFTER FROPA. VFR EXPECTED AFTER SUNRISE WITH NW WINDS 5-9 KT. EXTENDED OUTLOOK...VFR WED THROUGH FRIDAY. A CHANCE OF RAIN ON SATURDAY AND SUNDAY WITH POSSIBLE MVFR/IFR CONDITIONS. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 920 PM TUESDAY...WINDS ARE AT THEIR STRONGEST ACROSS THE COASTAL WATERS CURRENTLY, AROUND 20 KNOTS, AND SHOULD DIMINISH AS THE FRONT CROSSES OFFSHORE. AT 9 PM THE FRONT EXTENDS FROM WESTERN PENDER COUNTY ACROSS WHITEVILLE TO WESTERN HORRY COUNTY, MOVING EAST AT 25 KNOTS. THE BIGGEST CHANGE WITH THIS UPDATE WAS TO INCREASE SHOWER CHANCES ACROSS THE NC COASTAL WATERS BASED ON UPSTREAM RADAR IMAGERY AND MESOANALYSIS CONTINUING TO SHOW SMALL BUT POSITIVE INSTABILITY ALOFT. PREVIOUS DISCUSSION FROM 645 PM FOLLOWS... WINDS ARE A SOLID 20 KNOTS ACROSS THE COASTAL WATERS AND MAY ACTUALLY INCREASE TOWARD 25 KNOTS FOR A SHORT PERIOD BETWEEN 7-9 PM AHEAD OF THE COLD FRONT...NOW MOVING INTO THE WESTERN PORTIONS OF THE COASTAL PLAIN. THIS FRONT SHOULD PUSH OFF THE COAST LATE THIS EVENING WITH WINDS VEERING AROUND TO THE NW AND DIMINISHING TO 15 KNOTS OR LESS. SEAS HAVE BUILT TO 6 FEET OUT AT FRYING PAN SHOALS...WITH BUOYS CLOSER TO SHORE READING ANYWHERE FROM 2-5 FEET DEPENDING ON HOW OPEN THEY ARE TO FETCH FROM SW WINDS. THE BIGGEST CHANGE WITH THIS FORECAST UPDATE WAS TO INCREASE FORECAST WAVES ALONG THE BRUNSWICK COUNTY BEACHES BY ~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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ SYNOPSIS...8 NEAR TERM...TRA SHORT TERM...MJC LONG TERM...MBB AVIATION...MRR

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