Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 050642 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 242 AM EDT TUE MAY 5 2015 .SYNOPSIS... HIGH PRESSURE EXTENDING INTO THE AREA WILL CONTINUE TO DRIFT FARTHER OFFSHORE INTO MID-WEEK...PROVIDING SEASONABLE MAY WEATHER. A COASTAL LOW IS EXPECTED TO FORM IN THE BAHAMAS ON WEDNESDAY...DRIFTING NORTH BEFORE MEANDERING ALONG THE SOUTHEAST COAST FROM THURSDAY INTO NEXT WEEKEND. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... AS OF 1015 PM MONDAY...NO CHANGES TO THE FORECAST WITH THE LATEST UPDATE. PREVIOUS DISCUSSION FOLLOWS: CU FIELD HAS FADED WITH THE LOSS OF DAYTIME HEATING. SATELLITE LOOPS SHOW THAT WE MAY SEE SOME THIN CIRRUS PASS OVERHEAD AT TIMES...BUT OVERALL WE WILL SEE A CLEAR OVERNIGHT PERIOD. LIGHT S-SE WINDS WILL BECOME LIGHT AND VARIABLE BEFORE DECOUPLING THIS EVENING. THIS WILL BE A GOOD SETUP FOR RADIATIONAL COOLING AND TEMPS SHOULD FALL INTO THE MID 50S MOST LOCATIONS. FOG OF PATCHY TO AREAL EXTENT WILL BE POSSIBLE AFTER MIDNIGHT...ESPECIALLY INLAND WHERE THE TEMP-DEWPOINT DEPRESSION SPREAD WILL BE SMALLEST. && .SHORT TERM /6 AM THIS MORNING THROUGH WEDNESDAY NIGHT/... AS OF 3 PM MONDAY...EARLY SUMMER PATTERN WITH BERMUDA-LIKE HIGH CENTERED OFFSHORE...PROVIDING A BALMY EARLY MAY CIRCULATION OF AIR CLIMATOLOGICALLY INDICATIVE OF THE SEASON. MODERATE CUMULUS BUILD-UPS SEEMS LIKELY DURING THE AFTERNOON NEAR AND WEST OF THE THE AFTERNOON SEA-BREEZE...BUT ARID AIR ABOVE 10 THOUSAND FEET THROUGH WED AFTERNOON WILL KEEP MEASURABLE RAIN PROBABILITIES BELOW MENTIONABLE LEVELS. MAXIMUMS EITHER SIDE OF 80 DEG WARMEST OVER THE INTERIOR...AND MINIMUMS UPPER 50S TO LOW 60S EARLY WED AND 60-65 EARLY THU. A COASTAL LOW APPROACHING FROM THE SOUTH WILL BRING A SLIGHT CHANCE OF RAIN SHOWERS FAVORED ALONG THE COAST WED NIGHT INTO EARLY THURSDAY...AS LOW-LEVEL WIND DIRECTION AND WINDSPEED CONVERGENCE INCREASES OFFSHORE. && .LONG TERM /THURSDAY THROUGH MONDAY/... AS OF 3 PM MONDAY...ALL EYES REMAIN ON A LOW PRESSURE SYSTEM WHICH LOOKS LIKELY TO DEVELOP AND STRENGTHEN OFF THE SOUTHEAST COAST LATE THIS WEEK. NHC HAS ISSUED A SECOND SPECIAL TROPICAL WEATHER OUTLOOK TO ADDRESS THIS POTENTIAL...AND WHILE IT IS BECOMING MORE LIKELY A SYSTEM WILL DEVELOP...THERE IS STILL VERY LITTLE CONFIDENCE INTO HOW IT WILL MOVE ONCE FORMING. AN AREA OF MOISTURE ALREADY EVIDENT ACROSS THE CARIBBEAN/BAHAMAS TODAY WILL CONSOLIDATE AND LIFT SLOWLY NORTH TO OFF THE GA/SC COAST AT THE START OF THE EXTENDED. INITIALLY...THIS SYSTEM WILL FEED OF BAROCLINICITY AS AN ET-CYCLONE...BUT GUIDANCE SUGGESTS IT WILL TRANSITION TO A WARM CORE SYSTEM BY LATE WEEK AND POSSIBLY TAKE ON TROPICAL OR SUB-TROPICAL CHARACTERISTICS. THIS IS IMPORTANT BECAUSE THE ENVIRONMENT IS NOT ENTIRELY FAVORABLE FOR BAROTROPIC (WITHOUT TEMPERATURE GRADIENTS) STRENGTHENING THANKS TO WEAK DIFFLUENCE ALMOST EXCLUSIVELY ON THE EAST SIDE...AND WATER TEMPS WELL BELOW THE 80F THRESHOLD ONCE YOU GET OUTSIDE THE GULF STREAM. THIS SUGGESTS THAT A COMBINATION OF BAROTROPIC AND BAROCLINIC FEATURES WILL DETERMINE THE STRENGTH...HENCE THE LIKELY HYBRID-LOW. THE GUIDANCE STILL DIVERGES CONSIDERABLY ON THE LOW TRACK THANKS TO WEAK STEERING FLOW...BUT AS MENTIONED BY THE PREVIOUS FORECASTER...A TRACK DUE NORTH SEEMS IMPOSSIBLE WITH THE UPPER RIDGE IN THAT DIRECTION. THUS...A RETROGRADING W OR SW TRACK IS MOST PLAUSIBLE AND SEEMS TO BE SUPPORTED BY ENSEMBLES. STILL...THIS CREATES A VERY TRICKY FORECAST WITH A MEANDERING AND POSSIBLY STRENGTHENING LOW FOR SEVERAL DAYS OFF THE COAST. THE 12Z GFS BRINGS A PRETTY STRONG LOW INTO CENTRAL SC...BUT THIS IS A NEW SOLUTION FROM EVEN THE LAST RUN WHICH BROUGHT IT INTO THE GA COAST. THE ECMWF CONTINUES TO KEEP THE SYSTEM SPINNING JUST OFFSHORE INTO THE WKND. WHILE IT IS IMPOSSIBLE TO DETERMINE WITH ANY SPECIFICITY THE TRACK AT THIS TIME RANGE...WILL CONTINUE TO SHOW UNSETTLED WEATHER THU-SUN WITH THE BEST CHANCE FOR RAIN/WIND BEING LATE THURSDAY INTO SATURDAY. ALTHOUGH THE SYSTEM SHOULD BEGIN TO WEAKEN THEREAFTER...CONTINUED SCHC/LOW CHC POP IS WARRANTED RIGHT THROUGH THE END OF THE PERIOD BEFORE A TROUGH APPROACHES FOR EARLY NEXT WEEK WHICH WILL ACT TO FINALLY KICK OUT THE LOW. TEMPS THROUGH THE PERIOD SHOULD BE ABOVE CLIMO...BUT OF COURSE ANY SIGNIFICANT RAIN/CLOUDS COULD HINDER WARMING AND WILL ALSO BE DEPENDENT ON THIS LOW TRACK. ADDITIONALLY...E/NE WINDS OFF COOL SHELF WATERS WILL KEEP THE COASTAL AREAS MUCH COOLER THAN WELL INLAND...SO A LARGE TEMP GRADIENT ACROSS THE CWA IS POSSIBLE EACH AFTN THROUGH THE PERIOD. && .AVIATION /06Z 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... NEAR TERM /THROUGH TONIGHT/... AS OF 1015 PM MONDAY...NO CHANGES TO THE FORECAST WITH THE LATEST UPDATE. PREVIOUS DISCUSSION FOLLOWS: LATEST OBS SHOW A LIGHT SE FLOW OF AROUND 10 KTS WITH 2 FT SEAS OVER THE WATERS THIS EVENING. THIS SE FLOW WILL PERSIST OVERNIGHT AS HIGH PRESSURE LINGERS OVER THE WESTERN ATLANTIC...WITH SEAS OF 2 TO 3 FT THROUGHOUT THE WATERS. SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... AS OF 3 PM MONDAY...MANAGEABLE MARINE CONDITIONS MUCH OF THE PERIOD WITH INCREASING SEA HEIGHTS MAINLY LATE WEDNESDAY AS OFFSHORE SE-E WINDS BEGIN TO RAMP UP IN RESPONSE TO A BAHAMA COASTAL LOW DRIFTING NORTH. OTHERWISE...BERMUDA HIGH LIKE WEATHER WITH 2-3 FOOT SEAS AND AN INCREASE IN WIND GUSTS NEAR SHORE IN THE AFTERNOON TO EARLY EVENING DUE TO THE SEA BREEZE CIRCULATION. NO TSTMS EXPECTED THIS PERIOD...BUT SEAS MAY INCREASE TO 4-5 FT LATE WEDNESDAY NIGHT ACCOMPANIED BY INCREASING MARINE SHOWERS. LONG TERM /THURSDAY THROUGH SATURDAY/... AS OF 3 PM MONDAY...POTENTIAL CONTINUES FOR AN EXTENDED PERIOD OF POOR MARINE CONDITIONS THANKS TO A LOW PRESSURE SYSTEM THAT IS FORECAST TO DEVELOP AND POTENTIALLY TAKE ON TROPICAL CHARACTERISTICS THU-SAT. THERE IS STILL CONSIDERABLE UNCERTAINTY INTO THE STRENGTH AND TRACK OF THIS LOW...BUT IT LOOKS LIKELY THAT A SYSTEM WILL DEVELOP AND THEN MEANDER IN THE AREA THROUGH THE PERIOD. ATTM...IT APPEARS THE BEST COURSE OF ACTION IS A BLEND OF GUIDANCE...AND THIS CREATES E/NE WINDS OF 15-20 KTS THU/FRI...BEFORE EASING SATURDAY...HOPEFULLY. THIS EXTENDED PERIOD OF E/NE FETCH COMBINED WITH SWELL GENERATION FROM THE LOW PRESSURE...WILL DRIVE SEAS UP TO 4-8 FT THU AND FRI...BEFORE FALLING ON SATURDAY. OF COURSE THIS CAN CHANGE...AND THERE IS POTENTIAL FOR MUCH HIGHER SEAS AS THE WNAWAVE IS SHOWING 16 FT JUST OUTSIDE OF THE COASTAL WATERS FRIDAY. EITHER WAY...A LONG- DURATION STRONG SMALL CRAFT ADVISORY IS BECOMING MORE LIKELY FOR MUCH OF THE PERIOD. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ SYNOPSIS...MJC NEAR TERM...REK/CRM SHORT TERM...MJC LONG TERM...JDW AVIATION...DCH

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