Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 051746 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 145 PM EDT TUE MAY 5 2015 .SYNOPSIS... HIGH PRESSURE WILL CONTINUE TO PREVAIL THROUGH THE MID-WEEK PERIOD...AND PROVIDE SEASONABLE WEATHER. A COASTAL LOW IS EXPECTED TO FORM NEAR THE BAHAMAS WEDNESDAY...AND MEANDER OFF THE SOUTHEAST U.S. COAST THROUGH THE END OF THE WEEK. && .NEAR TERM /THROUGH TONIGHT/... AS OF 145 PM TUESDAY...ONSHORE FLOW WILL WEAKEN DURING THE EVENING AND ANY CUMULUS WILL DISSIPATE WITH THE LOSS OF HEATING. SKIES OVERNIGHT WILL BE MOSTLY CLEAR WITH SOME THIN HIGH CLOUDS POSSIBLE FROM THE AREA OF DISTURBED WEATHER FAR TO THE SOUTH. OTHERWISE... TIME HEIGHT CROSS SECTIONS INDICATE A DRY COLUMN IN THE H85-5 LAYER. WITH MOSTLY CLEAR SKIES AND LIGHT WINDS THINK A BLEND TOWARD THE COOLER MET NUMBERS WILL WORK TONIGHT...WHICH IS A NOTCH BELOW CLIMO. && .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 /18Z TUESDAY THROUGH SATURDAY/... AS OF 18Z...VFR THIS TAF VALID PERIOD. SURFACE HIGH PRESSURE WILL EXTEND WEST ACROSS THE TERMINALS FROM THE HIGH/S CENTER WELL OFFSHORE FROM CAPE HATTERAS. E-SE ONSHORE WINDS WILL AFFECT ALL TERMINALS THRU THIS PERIOD...ENHANCED BY THE SEA BREEZE THRU EARLY THIS EVENING...AND AFTER 14Z WEDNESDAY. THERE IS ENOUGH MOISTURE IN THE LOW LEVELS TO PRODUCE PRIMARILY DIURNALLY DRIVEN FEW/SCT CU....BUT OVERNIGHT SOME MARINE SC COULD PERSIST ESPECIALLY SE OF KMYR. NO LOW CIGS OR PRECIPITATION EXPECTED DUE TO SUBSIDENCE ALOFT LIMITING VERTICAL DEVELOPMENT. WINDS SUBSIDE THIS EVENING AND OVERNIGHT...AND WILL PICK UP AGAIN BY 14-15Z. ALTHOUGH THERE WILL BE PATCHY BR AFTER MIDNIGHT... CONFIDENCE IS LOW ANY SPECIFIC TERMINAL WILL BE AFFECTED FOR AN EXTENDED PERIOD OF TIME. EXTENDED OUTLOOK...VFR WED. LOW CONFIDENCE REMAINDER OF EXTENDED DUE TO UNCERTAINTY IN TRACK OF SUB-TROPICAL LOW APPROACHING THE TERMINALS. VFR LIGHT RAIN DEVELOPING EARLY THU WITH TEMPO MVFR BY THU AFTERNOON. RAIN/MVFR/WINDS FRI WITH TEMPO IFR. SAT TEMPO SHOWERS/MVFR. VFR SUN. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 130 PM TUESDAY...NORTHEAST TO EAST FETCH WILL PERSIST THROUGH TONIGHT WITH HIGH PRESSURE CENTERED OFFSHORE AND LOWERING PRESSURE IN THE VICINITY OF THE BAHAMAS. SEAS WILL GRADUALLY BUILD AS A RESULT OF THE PRESSURE GRADIENT...WITH CHOPPY 3-4 FT CONDITIONS POSSIBLE BY EARLY WEDNESDAY. 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. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ NEAR TERM...SRP SHORT TERM...III LONG TERM...III AVIATION...MRR/SRP

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