Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 040825 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 425 AM EDT MON MAY 4 2015 .SYNOPSIS...
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HIGH PRESSURE SYSTEM WILL CONTINUE TO DRIFT SLOWLY OFFSHORE THROUGH EARLY TO MID-WEEK...PROVIDING SUNSHINE AND SEASONABLE MAY TEMPERATURES. A COASTAL LOW IS EXPECTED TO FORM IN THE BAHAMAS MID-WEEK...AND MEANDER ALONG THE SOUTHEAST COAST THROUGH THE END OF THE WEEK AND INTO NEXT WEEKEND.
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&& .NEAR TERM /THROUGH TONIGHT/...
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AS OF 330 AM MONDAY...DRY AND SEASONABLE WEATHER WILL CONTINUE AS HIGH PRESSURE SLIPS FARTHER OFF SHORE WHILE CONTINUING TO RIDGE BACK INTO THE CAROLINAS. THIS WILL PROVIDE A LIGHT RETURN FLOW WITH A SLIGHT INCREASE IN MOISTURE. TEMPS DROPPING EARLY THIS MORNING WILL CREATE SOME VERY SHALLOW FOG BUT OVERALL COLUMN WILL REMAIN VERY DRY WITH ONLY LIMITED LOW LEVEL MOISTURE. A MID TO UPPER RIDGE TRIES TO BUILD OVERHEAD...BUT A SHORTWAVE RIDING DOWN FROM THE NW WILL DISRUPT THIS RIDGE AS IT MOVES SLOWLY OVER THE COASTAL CAROLINAS THROUGH THIS AFTERNOON WITH TROUGH BECOMING STRETCHED OUT ALONG THE COAST TONIGHT. AS THIS SHORTWAVE MOVES THROUGH IT WILL PRODUCE SOME PASSING MID LEVEL CLOUDS. THE LIGHT RETURN FLOW AROUND THE SFC HIGH WILL COMBINE WITH AFTERNOON SEA BREEZE TO GIVE IT A STRONG PUSH INLAND THROUGH THE AFTERNOON. CONVERGENCE ALONG THE SEA BREEZE AND THE WESTERN PERIPHERY OF HIGH PRESSURE WILL HELP BUILD SOME AFTERNOON CU. THE SHORTWAVE SHOULD ACT TO ENHANCE THE VERTICAL GROWTH A BIT...BUT A STRONG SUBSIDENCE INVERSION AROUND 8-9 K FT WILL CAP OFF THE CLOUDS AND LIMIT CHC OF SHWRS. THE HRRR TRIES TO GENERATE A FEW STRAY SHOWERS INLAND THIS AFTERNOON BUT BELIEVE THIS WILL JUST END UP BEING CLUSTERS OF CU. HUGE DIURNAL RANGES WILL CONTINUE WITH TEMPS STARTING OUT IN THE MID 50S THIS MORNING AND REACHING UP TO AROUND 80 EXCEPT SLIGHTLY COOLER AT THE BEACHES. CONTINUED ON SHORE FLOW AROUND HIGH WILL SUPPORT A SLOW RISE IN DEWPOINTS TONIGHT AFTER A DIURNAL DROP THIS AFTERNOON IN DEEPER MIXING. THIS WILL KEEP OVERNIGHT LOWS A FEW DEGREES HIGHER...BUT STILL DOWN TO 55 TO 60 MOST PLACES WITH IDEAL RADIATIONAL COOLING CONDITIONS UNDER CLEAR SKIES AND NEAR CALM WINDS. MAY SEE SOME PATCHY SHALLOW GROUND FOG AGAIN TONIGHT AS TEMPS DROP OUT BUT COLUMN WILL BE VERY DRY ABOVE THE SURFACE.
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&& .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... AS OF 3 AM MONDAY...BERMUDA HIGH ON TUESDAY WILL RETREAT WEDNESDAY AHEAD OF DISTURBANCE EMERGING FROM THE CARIBBEAN AND THE BAHAMAS. MID LEVEL RIDGING IN PLACE ABOVE THE BERMUDA HIGH TUE WILL MAINTAIN WARM AND DRY CONDITIONS ACROSS THE AREA WITH ONLY PATCHES OF SHALLOW AFTERNOON CU. ONSHORE FLOW WILL CONTINUE KEEPING TEMPS NEAR THE COAST AROUND CLIMO WHILE INLAND AREAS WARM UP A BIT. SECOND HALF OF THE PERIOD STARTS TO GET INTERESTING AS THE SYSTEM EMERGING FROM THE BAHAMAS WILL TRY AND COALESCE INTO A WELL DEFINED LOW. THE GOING WILL INITIALLY BE SLOW AND THE LACK OF STEERING FLOW ALOFT IS LIKELY TO KEEP THE SYSTEM SOUTH OF THE AREA THROUGH THE END OF THE PERIOD. STILL A LOT OF UNCERTAINTY REGARDING THIS SYSTEM AND WHILE IT MAY LEAD TO AN INCREASE IN CLOUD COVER...ESPECIALLY ALONG THE COAST WED NIGHT...DO NOT THINK IT WOULD DIRECTLY AFFECT THE REGION BEFORE THE END OF THE PERIOD. THUS WILL MAINTAIN THE DRY FORECAST WITH HIGHS AROUND CLIMO AND LOWS A BIT ABOVE CLIMO. && .LONG TERM /THURSDAY THROUGH SUNDAY/... AS OF 3 AM MONDAY...LONG TERM PERIOD WILL BE DOMINATED BY THE LOW EVOLVING OFF THE SOUTHEAST COAST MID TO LATE WEEK. GUIDANCE CONTINUES TO STRUGGLE WITH THIS SYSTEM...MAINLY DUE TO THE LACK OF ANY REAL STEERING FLOW ALOFT. HOWEVER SOME SOLUTIONS SEEM HARD TO BUY. FOR INSTANCE THE LOW DEEPENING AND MOVING UP THE COAST SEEMS THE LEAST LIKELY OUTCOME GIVEN THE 5H RIDGING TO THE NORTH. DO THINK THE LOW COULD GRADUALLY STRENGTHEN THROUGH THE PERIOD. ALTHOUGH THE WATER TEMPS WITHIN THE GULF STREAM ARE AROUND 80 AND SHEAR SHOULD BE WEAK TO NONEXISTENT THERE ARE SEVERAL FACTORS THAT WOULD LIMIT STRENGTHENING. A LACK OF DIFFLUENCE ALOFT EARLY IN THE PERIOD AND THE LARGE SWATH OF SEA SURFACE TEMPS OUTSIDE THE GULF STREAM IN THE 60S BEING THE BIGGEST. SO WHILE SOME DEVELOPMENT OF THIS SYSTEM IS EXPECTED A FULL BLOWN TROPICAL SYSTEM SEEMS TO BE A LONG SHOT. INSTEAD THE SYSTEM WILL PROBABLY ACQUIRE SOME TROPICAL CHARACTERISTICS BUT REMAIN QUITE WEAK AS IT WANDERS OVER THE WATERS OFF THE SOUTHEAST COAST. WORTH NOTING A LOT OF THE GFS ENSEMBLES TAKE THE WEAK LOW INTO FL OR SOUTHERN GA...SOMETHING WHICH A FAIR NUMBER OF THE MEMBERS HAVE BEEN CONSISTENTLY SHOWING OVER THE LAST FEW DAYS. LOCALLY IMPACTS THROUGH THE PERIOD WILL BE NORTHEAST FLOW...WITH SOME ENHANCEMENT LATER IN THE WEEK AND AN INCREASE IN LOW LEVEL MOISTURE. THIS SHOULD BRING ABOUT AN INCREASE IN PRECIP CHANCES...ESPECIALLY ALONG THE COAST...AS THE WEEK WEARS ON. GIVEN THE LOW CONFIDENCE PLAN TO MAKE ONLY SMALL CHANGES TO THE INHERITED FORECAST WHICH WILL NOW CARRY CHC POP THROUGH THE PERIOD WITH TEMPS NEAR TO SLIGHTLY ABOVE CLIMO. && .AVIATION /06Z MONDAY THROUGH FRIDAY/... AS OF 06Z...NOT MUCH SYNOPTICALLY DIFFERENT FROM YESTERDAY...WITH HIGH PRESSURE OFFSHORE GIVING US SOUTHEAST FLOW. THERE IS FOG POTENTIAL AGAIN OVERNIGHT...MAINLY AFTER 08Z. CRE STANDS THE BEST CHANCE AGAIN...BUT COULD NOT RULE OUT INLAND FOG EITHER. DO NOT THINK WE WILL SEE THE LIFR CONDITIONS THAT WE EXPERIENCED LAST NIGHT. MONDAY...BECOMING VFR AT ALL LOCATIONS WITH CONTINUED SOUTHEAST FLOW...STRONGEST ALONG THE COAST. 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...
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NEAR TERM /THROUGH TONIGHT/... AS OF 330 AM MONDAY...HIGH PRESSURE WILL SHIFT FARTHER OFF SHORE WHILE CONTINUING TO RIDGE BACK INTO THE COASTAL CAROLINAS. THEREFORE EXPECT A VERY LIGHT RETURN FLOW TO CONTINUE BASICALLY OUT OF THE SE-S LESS THAN 10 KTS. SEAS WILL RUN UNDER 3 FT MOST WATERS WITH A A VERY SLOW DECLINE THROUGH TODAY WITH SUCH LIGHT WINDS AND DIMINISHING LONGER PERIOD BACKSWELL FROM LOW MOVING OFF INTO THE DISTANT ATLANTIC WATERS. THE WNA SHOWS LONGER PERIOD SWELLS DROPPING OFF BY NOON TODAY WITH JUST SHORTER PERIOD WIND WAVES DOMINATING ESPECIALLY AS SEA BREEZE DEVELOPS THIS AFTERNOON. A PERSISTENT LIGHT ON SHORE RETURN FLOW WILL CAUSE A SLIGHT RISE IN SEAS THROUGH TONIGHT. OVERALL EXPECT BENIGN SEAS AROUND 2 TO 3 FT OR LESS WITH A SLIGHT SPIKE NEAR SHORE IN AFTERNOON SEA BREEZE. SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... AS OF 3 AM MONDAY...BERMUDA HIGH WILL MAINTAIN LIGHT EASTERLY FLOW TUE INTO WED. DURING THE SECOND HALF OF THE PERIOD THE HIGH WILL RETREAT NORTHEAST AS WEAK LOW PRESSURE EMERGES FROM THE BAHAMAS. WINDS WILL BACK TO NORTHEAST FOR WED AND WED NIGHT WITH A SLIGHT BUMP IS SPEED. CONFIDENCE WITH RESPECT TO THE AMOUNT OF STRENGTHENING THE LOW WILL UNDERGO AND ITS LOCATION IS RATHER LOW AND THUS FORECAST CONFIDENCE IS ALSO LOW. FOR NOW KEEPING WIND SPEEDS WED AND WED NIGHT CONFINED TO THE 15 TO 20 KT RANGE BUT HIGHER VALUES ARE POSSIBLE. SEAS 2 TO 3 FT TUE INTO WED SHOULD BUILD LATER WED AS NORTHEAST FLOW INCREASES AND COASTAL LOW STARTS TO BECOME A LITTLE MORE DEFINED. LONG TERM /THURSDAY THROUGH FRIDAY/... AS OF 3 AM MONDAY...MUCH OF THE FORECAST DEPENDS ON THE DETAILS OF THE HYBRID TROPICAL SYSTEM MEANDERING OFF THE SOUTHEAST COAST LATE THIS WEEK. WEAK STEERING FLOW ALOFT HAS SO FAR BEFUDDLED GUIDANCE AND NOT CONFIDENT CLARITY WILL DESCEND UPON THE FORECAST IN THE NEAR TERM. THAT SAID FEEL A FORECAST OF NORTHEAST FLOW IN THE 15 TO 20 KT RANGE IS A GOOD COMPROMISE AND IS IN LINE WITH PREVIOUS FORECASTS. SEAS WILL BUILD ON THE BACK OF EXTENDED NORTHEAST FLOW WITH SOME ZONES LIKELY TO EXCEED 6 FT IN PLACES ON THU AND REMAIN ABOVE 6 FT FRI.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ NEAR TERM...RGZ SHORT TERM...III LONG TERM...III AVIATION...RGZ/DL

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