Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 051100 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 700 AM EDT TUE MAY 5 2015 .SYNOPSIS...
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HIGH PRESSURE CENTERED OFFSHORE FROM CAPE HATTERAS WILL CONTINUE TO EXTEND INTO THE AREA THROUGH THE MID-WEEK PERIOD...AND PROVIDING SEASONABLE WEATHER FOR THIS TIME OF THE YEAR. A COASTAL LOW IS EXPECTED TO FORM IN THE BAHAMAS DURING THE MID-WEEK PERIOD...AND MEANDER ALONG OR OFF THE SOUTHEAST U.S. COAST BY THURSDAY AND CONTINUING THROUGH THE UPCOMING WEEKEND.
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&& .NEAR TERM /THROUGH TONIGHT/...
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AS OF 630 AM TUESDAY...BASICALLY LOOKING AT A PERSISTENCE TYPE FORECAST FOR THE NEXT 24 HRS...USING THE PREVIOUS 12-24 HRS AS GUIDANCE. RIDGING ALOFT TO PROVIDE SUBSIDENCE...THUS LIMITING THE VERTICAL DEVELOPMENT OF ANY DIURNALLY DRIVEN CU. SYNOPTICALLY DRIVEN ONSHORE WINDS WILL PERSIST ACROSS THE FA THIS PERIOD. THIS DUE TO THE POSITIONING OF THE EAST-WEST ORIENTED SFC RIDGE AXIS ACROSS THE NORTHERN PORTIONS OF FA. THIS AXIS EXTENDS FROM ITS PARENT HIGHS CENTER WELL OFFSHORE AND EAST OF CAPE HATTERAS. THE SEA BREEZE WILL DEVELOP BY MIDDAY AND LIKELY PROGRESS WELL INLAND TO THE I-95 CORRIDOR BY THE EARLY TO MID EVENING HRS BEFORE DISSIPATING. ENHANCED CU ALONG THIS BOUNDARY AS IT PUSHES INLAND WILL STILL HAVE STRONG ENOUGH SUBSIDENCE ALOFT TO PREVENT ANY CONVECTION FROM DEVELOPING. OTHER THAN DIURNALLY DRIVEN CU FOR SKY CONDITIONS...THIN CIRRUS WILL OCCASIONALLY PASS OVER...MAINLY ALONG THE IMMEDIATE COAST. AS FOR TEMPS...WILL AGAIN START OFF WITH PERSISTENCE...THEN POSSIBLY ADD 1 TO 2 DEGREES FOR TODAYS HIGHS AWAY FROM THE IMMEDIATE COAST...AND ADD 1 TO 2 DEGREES FOR THE TONIGHTS LOWS ACROSS ALL LOCATIONS DUE TO THE CONTINUED MARINE INFLUENCE AND ITS FURTHER PUSH INLAND. A PERSISTENT EASTERLY 2 TO 3 FOOT...9 TO 10 SECOND PERIOD GROUND SWELL...WILL CONTINUE TO BE THE PRIMARY DRIVER TO ENHANCE RIP CURRENT OCCURRENCE ACROSS ALL BEACHES TODAY...ESPECIALLY IN THAT 4 HR WINDOW CENTERED AT LOW TIDE.
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&& .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... AS OF 3 AM TUESDAY...WED WILL PROBABLY BE THE LAST DAY OF PLEASANT WEATHER ACROSS THE AREA...THOUGH THIS IS NOT CERTAIN. BERMUDA HIGH AND WEAK 5H RIDGING WILL RETREAT/WEAKEN DURING THE DAY...ALLOWING THE SYSTEM CONDENSING OFF THE SOUTHEAST COAST AN OPPORTUNITY TO START DRIFTING NORTH. SUBSIDENCE UNDER THE WEAKENING 5H RIDGE SHOULD BE STRONG ENOUGH TO KEEP SKIES SUNNY BUT EAST TO NORTHEAST FLOW WILL KEEP TEMPS ALONG THE COAST NEAR TO SLIGHTLY BELOW CLIMO WHILE INLAND AREAS SHOULD END UP ABOVE CLIMO. FORECAST BECOMES QUITE UNCERTAIN AS EARLY AS WED NIGHT WITH SOME OF THE GUIDANCE SHOWING PRECIP MOVING ONSHORE AFTER MIDNIGHT. HOWEVER HAVE LITTLE TO NO CONFIDENCE IN ANY ONE SOLUTION GIVEN THE LACK OF RUN TO RUN CONSISTENCY WITHIN THE GUIDANCE. THE GFS ENSEMBLES DO FAVOR A WEAK SYSTEM MOVING INTO CENTRAL OR SOUTHERN SOUTH CAROLINA LATE IN THE WEEK. THIS SOLUTION AT LEAST SEEMS PLAUSIBLE GIVEN THE LACK OF STEERING FLOW AND THE PRESENCE OF THE DISPLACED BERMUDA HIGH AND WEAK MID LEVEL RIDGING TO THE NORTH. DO NOT PLAN TO PULL INHERITED SLIGHT CHC/LOW CHC POP ALONG THE COAST WED NIGHT BUT REGION COULD VERY WELL REMAIN DRY. EITHER WAY PRECIP CHANCES SHOULD START TO RAMP UP DURING THE SECOND HALF OF THE PERIOD AS ABUNDANT LOW LEVEL MOISTURE IS SPREAD ONSHORE. CLOUD COVER AND NORTHEAST FLOW WILL KEEP HIGHS NEAR TO BELOW CLIMO THU WITH LOWS RUNNING NEAR TO ABOVE CLIMO THU NIGHT. && .LONG TERM /FRIDAY THROUGH MONDAY/... AS OF 3 AM TUESDAY...UNCERTAINTY ABOUNDS IN THE LONG TERM WITH THE MEANDERING SYSTEM OFF THE SOUTHEAST COAST THE FEATURE OF NOTE. BY THE START OF THE LONG TERM THE LOW SHOULD BE ACQUIRING AT LEAST SOME TROPICAL CHARACTERISTICS...THOUGH WHERE IT WILL BE WHEN ITS ACQUIRING THEM REMAINS A MYSTERY. WEAK STEERING FLOW ALOFT WILL KEEP THE LOWS MOVEMENT ERRATIC WHICH ALSO MAKES THE STRUCTURE AND STRENGTH FORECAST DIFFICULT. IF IT REMAINS IN THE VICINITY OF THE 80 DEGREE SSTS OF THE GULF STREAM IT WILL HAVE LITTLE TO INHIBIT IT FROM GAINING STRENGTH. OF COURSE OUTSIDE THE GULF STREAM SSTS ARE MUCH COOLER...WITH SOME AREAS STILL IN THE 60S. THIS WOULD KEEP THE LOW WEAK AND DISORGANIZED. THIS SOLUTION SEEMS TO BE WHAT THE GFS ENSEMBLES HAVE BEEN KEYING ON AND WHAT THE LATEST GFS IS HINTING AT. THESE RECENT DEVELOPMENTS COMBINED WITH THE 12Z ECMWF SOLUTION OF A WEAKER MEANDERING LOW INSPIRES A HINT OF CONFIDENCE...THOUGH NOT ENOUGH TO MAKE DRASTIC CHANGES TO THE FORECAST. REGARDLESS OF THE EXACT LOCATION OF THE FEATURE THERE IS LIKELY TO BE A LOT OF LOW LEVEL MOISTURE OVER THE SOUTHEAST THROUGH THE PERIOD GIVEN THE PROLONGED ONSHORE FLOW. THERE WILL ALSO BE DAYTIME HEATING AND AN OVERALL LACK OF STRONG DOWNWARD MOTION...EVEN IF THE LOW IS DISPLACED WELL OFF THE COAST. THIS IS A RECIPE FOR AT LEAST SHOWERS EVERYDAY WITH POTENTIAL FOR ISOLATED THUNDERSTORMS AS WELL. THE INHERITED FORECAST FITS THIS QUITE WELL THOUGH DID BUMP UP POP OVER THE WEEKEND BUT KEPT EVERYWHERE CONFINED TO LOW CHC RANGE. WHAT IS LEFT OF THE LOW SHOULD DISSIPATE EARLY NEXT WEEK AHEAD OF POTENTIAL SHORTWAVE TROUGH. AS HAS BEEN THE CASE RECENTLY THE GFS/ECMWF ARE AT ODDS OVER THE EVOLUTION OF THE MID LEVEL PATTERN NEXT WEEK. THE GFS HOLDS ONTO THE SOUTHWEST CUTOFF...EJECTING SHORTWAVES ACROSS THE SOUTHERN CONUS. THE ECMWF STARTS TO FILL THE CUTOFF AND LIFTS IT NORTHEAST...REACHING THE AREA AS THE PERIOD ENDS. BOTH SOLUTIONS RESULT IN SOMEWHAT SIMILAR RESULTS...AT LEAST CHC POP TO END THE PERIOD WITH TEMPS NEAR CLIMO. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/... AS OF 06Z...WILL LEAN TOWARD PERSISTENCE FOR THE 06Z FORECAST ISSUANCE PERIOD. SFC RIDGE AXIS WILL EXTEND WEST ACROSS THE NC-SC AREA FROM THE HIGHS CENTER WELL OFFSHORE FROM CAPE HATTERAS. LOOKING AT ONSHORE FLOW ACROSS ALL TERMINALS THRU THIS PERIOD... ENHANCED BY THE SEA BREEZE LATE THIS MORNING THRU EARLY-MID THIS EVENING. ENOUGH MOISTURE IN THE LOW LEVELS TO PRODUCE DIURNALLY DRIVEN FEW/SCT CU BUT NO PCPN EXPECTED DUE TO SUBSIDENCE ALOFT LIMITING VERTICAL DEVELOPMENT. EXTENDED OUTLOOK...MVFR/IFR CONDITIONS FOR A 2 TO 3 HR WINDOW FOR BR AND POSSIBLY FG IN THE VICINITY OF DAWN EACH DAY. UNSETTLED WEATHER THURSDAY NIGHT INTO THE WEEKEND FROM A SPORADIC MOVING LOW OFF THE SE U.S. COAST. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 630 AM TUESDAY...WILL BASICALLY USE A PERSISTENT TYPE FORECAST FOR WINDS AND SIGNIFICANT SEAS BASED ON THE PREVIOUS 12 TO 24 HRS. MODELS BASICALLY INDICATE THE SFC RIDGE AXIS WILL EXTEND WEST ACROSS THE AREA WATERS FROM THE HIGHS CENTER LOCATED WELL OFFSHORE FROM CAPE HATTERAS. THIS WILL KEEP THE HIER ONSHORE EASTERLY WINDS JUST SOUTH OF THE AREA WATERS...AND THE HIGHER SSW- SW WINDS WELL NORTH OF THE AREA WATERS. THEREFORE WIND SPEEDS WILL HANG AROUND 10 KT...EXCEPT THE NEAR SHORE WATERS DURING THIS AFTERNOON AND EARLY EVENING COULD OBSERVE 10-15 KT OR POSSIBLY A SOLID 15 KT DEPENDING ON THE STRENGTH OF THE INLAND PROGRESSING SEA BREEZE. SIGNIFICANT SEAS WILL MAINLY BE GOVERNED BY A 2 TO POSSIBLY 3 FOOT 9 SECOND EASTERLY GROUND SWELL. THE LONG FETCH ASSOCIATED WITH THE EASTERLY ONSHORE FLOW SOUTH OF THE SFC HIGH CENTERED WELL OFFSHORE FROM CAPE HATTERAS WILL PROVIDE THIS SWELL. WIND DRIVEN WAVES AT 3.5 TO 4.5 SECOND PERIODS ESPECIALLY NEARSHORE DUE TO THE SEA BREEZE WILL PROVIDE SOME CHOP. NEVERTHELESS...THE EASTERLY GROUND SWELL WILL REMAIN QUITE VISIBLE. SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... AS OF 3 AM TUESDAY...LIGHT NORTHEAST FLOW AT THE START OF THE PERIOD WILL GRADUALLY INCREASE. THE MAGNITUDE OF THE INCREASE REMAINS IN QUESTION AS CONFIDENCE IN THE EVOLUTION OF THE LOW DEVELOPING NORTH OF THE BAHAMAS DURING THE PERIOD IS LOW. IT DOES NOT APPEAR A FULL BLOWN TROPICAL SYSTEM WILL DEVELOP DURING THE PERIOD BUT THE LOW IS EXPECTED TO EXPERIENCE AT LEAST SOME STRENGTHENING. THE COMBINATION OF EXTENDED NORTHEAST FLOW AND SPEEDS SOLIDLY IN THE 15 TO 20 KT RANGE LATER IN THE PERIOD WILL PUSH SEAS OVER 6 FT AS EARLY AS THU AM AND HEADLINES ARE LIKELY TO BE REQUIRED FOR AT LEAST THE SECOND HALF OF THE PERIOD. LONG TERM /FRIDAY THROUGH SATURDAY/... AS OF 3 AM TUESDAY...LOCATION AND STRENGTH OF THE LOW OFF THE SOUTHEAST COAST REMAINS IN QUESTION...BUT ITS PRESENCE WILL AT THE VERY LEAST LEAD TO CONTINUED NORTHEAST FLOW. SPEEDS COULD APPROACH 25 KT AT TIMES...FURTHER BUILDING SEAS WITHIN 20 NM. IT SEEMS ALMOST CERTAIN THAT HEADLINES WILL BE REQUIRED FOR AT LEAST SOME PORTION OF THE FORECAST PERIOD THOUGH THE NATURE OF THE HEADLINES AND THEIR DURATION WILL DEPEND SOLELY ON THE EVOLUTION OF THE LOW OFF THE SOUTHEAST COAST. CONFIDENCE IN ANY ONE SOLUTION IS LOW SO DID NOT MAKE MUCH IN THE WAY OF CHANGES.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ SYNOPSIS...III NEAR TERM...DCH SHORT TERM...III LONG TERM...III AVIATION...DCH

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