Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 041420 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 1020 AM EDT MON MAY 4 2015 .SYNOPSIS... HIGH PRESSURE WILL CONTINUE TO DRIFT SLOWLY OFFSHORE 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. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1000 AM MONDAY...THE ATMOSPHERIC COLUMN IS RELATIVELY DRY OVERALL...HOWEVER 12Z SOUNDINGS FROM MHX AND CHS DO SHOW A LAYER OR MOISTURE JUST BELOW 700 MB. THIS MOISTURE IS EVIDENT IN VISIBLE SATELLITE IMAGERY AS A LAYER OF SCATTERED CLOUDS MOVING SSW AROUND H7-H8 HIGH PRESSURE CENTERED OVER CLT. WEAK MID-LEVEL TROFFINESS WILL SLIDE ACROSS THE AREA THIS AFTERNOON WHILE MODEST LOW- LEVEL RETURN FLOW SETS UP AROUND OFFSHORE SURFACE HIGH. HRRR INDICATES SOME POTENTIAL FOR LIGHT SHOWERS INLAND BY EARLY AFTERNOON AHEAD OF THE SEA BREEZE...BUT MOISTURE WILL BE THE LIMITING FACTOR. DO NOT PLAN TO ADD POPS TO THE FORECAST AT THIS TIME BUT CAN NOT RULE OUT A FEW BRIEF...LIGHT SHOWERS ACROSS THE WESTERN 2/3 OF THE CWA. NO CHANGE NEEDED TO MAX TEMP FORECAST... WITH AN EXPECTED RANGE OF MID-UPPER 70S AT THE BEACHES TO LOW 80S INLAND. CONTINUED ON SHORE FLOW TONIGHT AROUND OFFSHORE HIGH WILL SUPPORT A SLOW RISE IN DEWPOINTS AFTER A DIURNAL DROP THIS AFTERNOON IN DEEPER MIXING. THIS WILL KEEP OVERNIGHT LOWS A FEW DEGREES HIGHER THAN LAST NIGHT...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. && .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 /14Z MONDAY THROUGH FRIDAY/... AS OF 06Z...PERSISTENCE FORECAST REGARDING AVIATION PURPOSES. BERMUDA HIGH PRESSURE WILL CONTINUE TO DOMINATE WX CONDITIONS THROUGH THE PERIOD WITH MOSTLY IFR CONDITIONS. SOME MODELS ARE GENERATING A LITTLE SEA BREEZE ACTIVITY ACROSS SOUTH CAROLINA BUT FEEL ANY ACTIVITY WILL BE TOO ISOLATED IN NATURE TO INCLUDE IN FORECAST. ADDED A LITTLE BR TO FLO FOR THE OVERNIGHT HOURS PER OBSERVATIONS THIS MORNING. 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 1000 AM MONDAY...EXPECT ISOLATED SHOWERS CREEPING WESTWARD TOWARDS CAPE FEAR TO DIMINISH AS THEY BECOME INFLUENCED BY THE DOWNWARD COMPONENT OF THE SEA BREEZE CIRCULATION. OTHERWISE...ESE FLOW WILL BE THE STORY FOR THE REMAINDER OF THE DAY DUE TO SURFACE HIGH PRESSURE WELL OFF THE NC COAST. WIND SPEEDS AROUND 10 KNOTS ARE EXPECTED AS THE PRESSURE GRADIENT WILL REMAIN BENIGN THROUGH THE PERIOD. 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. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ SYNOPSIS...SHK NEAR TERM...CRM SHORT TERM...III LONG TERM...III AVIATION...SHK MARINE...

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