Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 042210 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 609 PM EDT MON MAY 4 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...DRIFT NORTH THEN MEANDER ALONG THE SOUTHEAST COAST FROM THURSDAY INTO NEXT WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... AS OF 3 PM MONDAY...FIELD OF SHALLOW CU HAS DEVELOPED IN WEST OF THE SEA BREEZE THIS AFTERNOON. THIS CLOUD COVER WILL DISSIPATE QUICKLY AFTER SUNSET AND LIGHT S-SE WINDS WILL BECOME LIGHT AND VARIABLE BEFORE LIKELY DECOUPLING. THIS WILL BE A GOOD SETUP FOR RADIATIONAL COOLING AND TEMPS SHOULD FALL INTO THE MID 50S MOST LOCATIONS. SOME PATCHY FOG WILL BE POSSIBLE IN THE FEW HOURS BEFORE SUNRISE...ESPECIALLY INLAND WHERE THE TEMP-DEWPOINT DEPRESSION WILL BE SMALLEST. && .SHORT TERM /TUESDAY 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 /00Z TUESDAY THROUGH SUNDAY/... AS OF 00Z...MUCH THE SAME AS YESTERDAY WITH HIGH PRESSURE OFFSHORE CONTROLLING THE WEATHER. THERE IS ANOTHER CHANCE FOR FOG TONIGHT MAINLY THE USUAL SUSPECTS...CRE AND FOG. POCKETS OF IFR ARE POSSIBLE BUT SHOULD BE SHORT LIVED. TUESDAY...CONTINUED LIGHT SOUTHEAST FLOW WITH CU FORMING BY MID MORNING BUT MOVING QUICKLY INLAND WITH THE RESULTANT. EXTENDED OUTLOOK...PRE-DAWN MORNING FOG IS POSSIBLE EACH DAY THAT COULD RESULT IN MVFR/IFR CONDITIONS. UNSETTLED WEATHER THURSDAY NIGHT THROUGH SATURDAY WITH A SUBTROPICAL LOW. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 3 PM MONDAY...ISOLATED SHOWERS 10-20 NM OFF THE CAPE FEAR COAST HAVE STRUGGLED TO SURVIVE AS THEY ENCROACH ON THE RELATIVELY COOL SHELF WATERS AND ENCOUNTER SOME DOWNWARD MOTION RESULTING FROM THE SEA BREEZE. IF DISSIPATION TREND CONTINUES WILL PROBABLY NOT INCLUDE ANY POP FOR THE LATE AFTERNOON. OTHERWISE...SE FLOW WILL PERSIST OVERNIGHT AROUND SURFACE HIGH PRESSURE WHICH WILL LINGER OFF THE NC COAST OVERNIGHT. 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...8 NEAR TERM...CRM SHORT TERM...MJC LONG TERM...JDW AVIATION...43

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