Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 180252 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 952 PM EST WED DEC 17 2014 .SYNOPSIS... HIGH PRESSURE WILL RIDGE INTO THE CAROLINAS THROUGH FRIDAY. LOW PRESSURE WILL MOVE ALONG THE COAST SATURDAY...BRINGING WIDESPREAD RAIN AND BELOW NORMAL TEMPERATURES. A DRYING TREND WILL DEVELOP INTO EARLY NEXT WEEK...ALONG WITH WARMING TEMPERATURES. ANOTHER COLD FRONT WILL APPROACH LATE TUESDAY. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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AS OF 930 PM WEDNESDAY... THE SECONDARY COLD FRONT/SURGE LINE HAS REACHED SOUTHERN VIRGINIA. LATEST HIGH-RES MODELS INDICATE THE BOUNDARY SHOULD PUSH THROUGH SE NORTH CAROLINA BETWEEN 200-330 AM...AND NE SOUTH CAROLINA BETWEEN 300-600 AM...HERALDED BY A SHIFT TO NORTH WINDS. INFRARED SATELLITE SHOWS A THIN OVERCAST ACROSS MOST OF NORTH CAROLINA WITH LESS CLOUDINESS ACROSS SOUTH CAROLINA. A PEEK UPWARDS FROM THE OFFICE PARKING LOT JUST MINUTES AGO SHOWS PLENTY OF BRIGHT STARS SHINING THROUGH BUT AN INDISTINCT MILKINESS OBSCURING THE DIMMER ONES. SKY COVER FORECASTS TRENDING TOWARD PARTLY CLOUDY ARE PROBABLY THE BEST WAY TO GO FOR THE REST OF THE NIGHT. DEWPOINTS AT THE COAST HAVE FALLEN BACK INTO THE 30S AND LOWER 40S. 00Z SOUNDINGS FROM MHX AND CHS SHOW TOO STEEP A HYDROLAPSE IN THE LOWEST COUPLE THOUSAND FEET OF THE ATMOSPHERE FOR SIGNIFICANT FOG...SO I HAVE REMOVED IT FROM THE FORECAST. LITTLE CHANGE HAS BEEN MADE TO OVERNIGHT LOW TEMP FORECASTS: LOWS ARE STILL ANTICIPATED TO REACH 35-40 FOR MOST AREAS BY DAYBREAK. PREVIOUS DISCUSSION FROM 630 PM FOLLOWS... LIGHT WEST WINDS IN ADVANCE OF A SECONDARY COLD FRONT/SURGE LINE WILL PROBABLY BECOME CALM HERE AT THE SURFACE IN THE NEXT HOUR. WITH DEWPOINTS REBOUNDING INTO THE 40S OUTSIDE OF THE SANDHILLS THIS OPENS THE POTENTIAL FOR FOG DEVELOPING THIS LATER THIS EVENING. A GRADUAL INCREASE IN CIRRUS CLOUD COVER AND MORE IMPORTANTLY THE ADVANCING FRONT/SURGE WILL DISTURB THE BOUNDARY LAYER SUFFICIENTLY AFTER MIDNIGHT TO ERODE ANY FOG THAT DEVELOPS...PROBABLY IN THE 2-4 AM TIMEFRAME. CHANGES WITH THIS NEAR-TERM UPDATE CENTER ON HOURLY FORECAST TEMPS/DEWPOINTS/WINDS/FOG POTENTIAL. PREVIOUS DISCUSSION FROM 300 PM FOLLOWS... THE WEAK CYCLONIC FLOW AROUND POTENT LOW PRESSURE MOVING OFF THE CANADIAN MARITIMES WILL WEAKEN THROUGH THE AFTERNOON AS A ZONAL MID LEVEL FLOW PERSISTS. WEAK HIGH PRESSURE WILL BUILD IN FROM THE NORTHWEST OVERNIGHT WHICH WILL ONLY SERVE TO DAMPEN TEMPERATURES A BIT THURSDAY. FOR THIS AFTERNOON AND OVERNIGHT...THE ONLY ISSUE IS HIGH CLOUD COVER STREAMING IN FROM THE SOUTHWEST. THE GFS 200MB RH FIELDS CAPTURES THIS FAIRLY WELL. I HAVE INCREASED CLOUD COVER A BIT VERY LATE AS WELL AS ADDING PATCHY FOG AS LIGHT WINDS AND SOME RADIATIONAL COMPONENT WARRANT. WENT WITH THE COOLER NAM/MET NUMBERS FOR LOWS.
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&& .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... AS OF 300 PM WEDNESDAY...QUIET WEATHER FOR MUCH OF THE SHORT TERM PERIOD WILL COME TO AN END LATE FRI AS POPS FINALLY RETURN TO THE FORECAST. A WEAK BACK DOOR COLD FRONT WILL DROP SOUTHWARD ACROSS THE FORECAST AREA ON THU MORNING...THOUGH THERE WILL NOT BE ANY PRECIP ASSOCIATED WITH THIS FEATURE. SLIGHTLY COOLER AIR WITHIN THE SHALLOW NORTHERLY FLOW BEHIND THE FRONT WILL KEEP HIGH TEMPS NEAR SEASONABLE VALUES ON THU AND FRI...GENERALLY MID TO UPPER 50S WITH LOWER 60S POSSIBLE IN THE PEE DEE REGION. LOWS WILL FALL INTO THE MID 30S THU NIGHT. A SOUTHERN STREAM SHORTWAVE WILL MOVE ACROSS TX FRI MORNING AND CONTINUE RACING ACROSS THE SOUTHEAST DURING THE DAY. THIS WILL HELP INDUCE CYCLOGENESIS ALONG THE GULF COAST LATE FRI. ALTHOUGH THIS LOW WILL STAY WELL TO OUR SOUTHWEST DURING THIS SHORT TERM PERIOD... MOIST OVERRUNNING ALONG THE 300K SURFACE WILL ALLOW LIGHT RAIN TO SPREAD ACROSS THE AREA FROM SW TO NE OVERNIGHT FRI. LOOKING AT THE FCST SOUNDINGS...IT WILL TAKE SOME TIME TO OVERCOME THE DRY AIR BELOW 600 MB EVEN AFTER 06Z SAT. ADDITIONALLY...THE LATEST SREF PROBS SUGGEST MEASURABLE PRECIP WILL HOLD OFF UNTIL SAT MORNING AT KILM AND OUR NORTHEAST ZONES. FOR THESE REASONS...WILL TRIM BACK POPS AND QPF...ESPECIALLY ACROSS THE CAPE FEAR REGION. STILL HAVE INCLUDED CHC TO LIKELY POPS AT ALL LOCATIONS BY THE END OF THE PERIOD...BUT MOST OF THE LOCAL IMPACTS FROM THIS SYSTEM WILL BE CONFINED TO SAT. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... AS OF 300 PM WEDNESDAY...DEEP LAYER SATURATION EITHER UNDERWAY OR JUST ABOUT COMPLETE AT THE START OF THE PERIOD. HIGH PRESSURE WILL BE CENTERED NORTH OF NEW ENGLAND STATES AND HAVE A RIDGE AXIS EXTENDING ALL THE WAY DOWN INTO THE CAROLINAS. A SURFACE AND LOW LEVEL LOW WILL MEANWHILE BE TRAVERSING THE GULF STATES/FLORIDA PANHANDLE AREA. THIS LEADS TO FAIRLY DEEP BUT ALSO SOMEWHAT GENTLE ISENTROPIC UPGLIDE. IT`LL BE INTERESTING TO SEE HOW MUCH RAIN THIS YIELDS WHEN ALL IS SAID AND DONE AS HINTED AT BY SOME DIFFERING MODEL OPINIONS. THE WRF SHOWS A FAIRLY EVEN DISTRIBUTION OF PRECIPITATION AT LEAST THROUGH ITS MAIN 84 HOUR FCST WINDOW TO SAT EVE. THE GFS ON THE OTHER HAND IS SUPPRESSING HIGHEST QPF OVER SRN ZONES...WHICH MAY BE IN DEFERENCE TO THE DRY AIR BEING SUPPLIED BY THE SFC WEDGE. THE CMC LARGELY AGREES WITH THIS OPINION AND SO THE FORECAST HAS BEEN MINORLY TWEAKED ACCORDINGLY. BY EVENING THE DEPTH OF THE MOISTURE WILL BE ON THE WANE AND THE UPGLIDE PRETTY MUCH SHUTS OFF. LOW LEVEL MOISTURE LINGERS SAT NIGHT INTO SUNDAY IN ASSOC WITH THE CONTINUED WEDGING, THIS MOISTURE TRAPPED UNDER AN INVERSION AS THE SURFACE LOW SKIRTS OFF TO THE NORTH AND EAST FAIRLY QUICKLY. BY MONDAY THE WEDGE APPEARS TO HAVE WASHED OUT WHICH MAY ALLOW FOR THE LOW LEVEL MOISTURE TO MIX MORE DEEPLY LOWERING THE OVERALL RELATIVE HUMIDITY BY ENTRAINING DRY AIR FROM ABOVE...I.E. SUNSHINE SHOULD RETURN. MOISTURE AND WARM ADVECTION UNDERWAY ON TUESDAY AS NEXT DEEP TROUGH GETS DUG OUT, THIS ONE FURTHER WEST. THIS SYSTEM SHOULD BRING SHOWERS TUESDAY NIGHT INTO WEDNESDAY, THUNDERSTORMS APPEAR POSSIBLE AND MAY BE STRONG IF THE FAIRLY POTENT LOOKING GFS SOLUTION COMES TO PASS. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... AS OF 00Z...VFR AT THE TERMINALS THIS EVENING WITH CALM/LGT SW WINDS. WINDS WILL BECOME LGT NW-N ALL TERMINALS OVERNIGHT. THERE IS A CHANCE PATCHY BR WILL DEVELOP IN THE PRE-DAWN HOURS WITH TEMPO MVFR VSBYS POSSIBLE. SOUNDINGS DO NOT SUPPORT DENSE FOG. VFR EXPECTED AFTER SUNRISE WITH N-NE WINDS BECOMING LGT E IN THE LATE AFTERNOON. EXTENDED OUTLOOK...VFR THROUGH FRIDAY. GOOD CHANCE OF RAIN ON SATURDAY WITH POSSIBLE MVFR/IFR CONDITIONS. A SLIGHT CHANCE OF PRECIP ON SUN AND MON. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 930 PM WEDNESDAY...WINDS ARE VEERING MORE WESTERLY...ALBEIT MORE SLOWLY THAN I ANTICIPATED ALONG THE SC COAST. THE FRONT/SURGE LINE IS DROPPING SOUTH ACROSS SOUTHERN VIRGINIA CURRENTLY...WITH THE 23Z HIGH-RES MODEL RUNS SHOWING A 3-6 AM TIMING FOR THE WIND SHIFT FROM CAPE FEAR DOWN TO WINYAH BAY. SEAS CONTINUE AROUND 2 FEET WITH THE BULK OF THE WAVE ENERGY IN A 10 SECOND SE SWELL. SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... AS OF 300 PM WEDNESDAY...EXPECT NORTH WINDS AROUND 10 KT DURING THE DAY THU BEHIND A WEAK COLD FRONT. SEAS WILL REMAIN AROUND 2 FT THU THROUGH MUCH OF FRI AS THE GRADIENT REMAINS FAIRLY RELAXED OVER THE WATERS. A SURFACE LOW WILL BEGIN TO TAKE SHAPE ALONG THE GULF COAST LATE FRI...AND IN RESPONSE THE GRADIENT OVER THE WATERS WILL TIGHTEN BETWEEN THIS LOW AND HIGH PRESSURE BUILDING DOWN FROM THE NORTH. WINDS FRI NIGHT WILL BECOME NORTHEAST 10 TO 15 KT...AND SEAS WILL BUILD TO 3 FT WITH A DOMINANT NE WIND CHOP AND A WEAK BACKGROUND SE SWELL. LONG TERM /SATURDAY THROUGH MONDAY/... AS OF 300 PM WEDNESDAY...ALTHOUGH NOT A BANNER DAY FOR SAILING DUE TO WIDESPREAD RAIN NO ADVISORY OR HEADLINES EXPECTED ON SATURDAY IN A WEATHER SITUATION THAT CAN SOMETIMES YIELD EITHER. HIGH PRESSURE WEDGING IN FROM THE NORTH WHILE STORM SYSTEM STRENGTHENS SLOWLY AND MOVES FROM THE GULF STATES INTO THE FLORIDA PANHANDLE. AS THE LOW BEGINS TO EXIT TO THE NORTH AND EAST WINDS WILL BACK IN DIRECTION WITH LITTLE EFFECT ON SEAS SAVE A SMALL INCREASE IN THE BRUNSWICK COUNTY NEARSHORE WAVE SHADOW. HEADING INTO MONDAY BRINGS A WEAKENING OF THE OVERLAND HIGH PRESSURE AND THUS A WIND THAT TURNS A BIT OFFSHORE AND WEAKENS CONSIDERABLY, LIKELY DROPPING TO 10KT OR LESS.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ NEAR TERM...TRA SHORT TERM...BJR LONG TERM...MBB AVIATION...MRR

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