Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 301045 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 645 AM EDT SAT AUG 30 2014 .SYNOPSIS...
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STRENGTHENING BERMUDA HIGH PRESSURE OFFSHORE WILL BRING WARM WEATHER THROUGH THE LABOR DAY WEEKEND WITH A FEW AFTERNOON SHOWERS AND THUNDERSTORMS POSSIBLE. A WEAK COLD FRONT WILL APPROACH FROM THE NORTH LATE IN THE PERIOD BUT IS LIKELY TO STALL BEFORE REACHING THE AREA. BERMUDA HIGH PRESSURE AND A PIEDMONT TROUGH WILL REMAIN THE DOMINANT FEATURES INTO NEXT WEEKEND.
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&& .NEAR TERM /THROUGH TONIGHT/...
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AS OF 645 AM SATURDAY...LOW CLOUDS AND FOG HAVE FILLED IN ACROSS THE SC PEE DEE CORRIDOR FROM GEORGETOWN AND KINGSTREE NORTHWARD ACROSS FLORENCE TO DARLINGTON AND BENNETTSVILLE. THE OVERNIGHT RUNS OF THE HRRR HAVE BEEN NEARLY PERFECT PREDICTING THE AREA AFFECTED BY THESE CLOUDS. SURFACE VISIBILITIES SHOULD IMPROVE SHORTLY NOW THAT THE SUN IS RISING...BUT IT TAKE ANOTHER 2-3 HOURS FOR THE LOW STRATUS TO BURN OFF INTO A CUMULUS DECK. NO SIGNIFICANT CHANGES ARE NEEDED TO THE FORECAST. PREVIOUS DISCUSSION FROM 300 AM FOLLOWS... MID AND UPPER LEVEL HIGH PRESSURE WILL BE ALMOST DIRECTLY OVERHEAD TODAY. THIS WILL KEEP THE FLOW OF TROPICAL MOISTURE ORIGINATING FROM THE WESTERN GULF ROUTED UP THE MISSISSIPPI RIVER VALLEY INTO THE GREAT LAKES WITH NO IMPACT THIS FAR EAST. AT THE SURFACE A PESKY LITTLE BACKDOOR COLD FRONT APPEARS TO HAVE SUNK AS FAR SOUTH AS NORTHERN PENDER AND BLADEN COUNTIES THIS MORNING. THIS BOUNDARY MAY ACTUALLY LINGER ACROSS SOUTHEASTERN NORTH CAROLINA FOR MUCH OF THE MORNING BEFORE RETURNING NORTH EARLY THIS AFTERNOON...PUSHED BY A COMBINATION OF THE LOCAL SEABREEZE CIRCULATION PLUS A SLOW VEERING OF THE SYNOPTIC WIND AS HIGH PRESSURE MOVES FARTHER EAST OFF THE NEW ENGLAND COASTLINE. ALTHOUGH THERE IS NO SYNOPTIC FORCING PRESENT TODAY...AN UNSTABLE AIRMASS WILL DEVELOP WITH SURFACE-BASED CAPE RISING TO 1500 J/KG AT THE COAST AND NEAR 1000 J/KG INLAND. ONLY ISOLATED SHOWERS ARE EXPECTED...MAINLY EAST OF I-95. IN TERMS OF TIMING...THE BETTER SHOWER CHANCES MAY ACTUALLY OCCUR DURING THE MORNING AND EARLY AFTERNOON HOURS WITH DEEPER MIXING DURING THE AFTERNOON DRAGGING DOWN DRY AIR FROM ALOFT AND DILUTING THE SURFACE-BASED INSTABILITY. PLENTY OF DRY AIR ALOFT AND VERY WEAK WINDS THROUGHOUT THE TROPOSPHERE FAVOR ONLY SMALL THUNDER CHANCES AND NO STORM-CELL ORGANIZATION. HIGHS TODAY SHOULD RISE INTO THE LOWER 90S INLAND WITH UPPER 80S NEAR THE COAST. MOSTLY CLEAR TO PARTLY CLOUDY SKIES AND LIGHT WINDS WILL AGAIN FAVOR AREAS OF LOW CLOUDS AND/OR FOG LATE TONIGHT. LOWS SHOULD FALL TO NEAR 70.
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&& .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 3 AM SATURDAY...WEAKENING MID LEVEL RIDGE ON SUN WILL STILL BE WORKING TO LIMIT AFTERNOON CONVECTION. FORECAST SOUNDINGS SHOW AN ABUNDANCE OF MID LEVEL DRY AIR AND A WEAK SUBSIDENCE INVERSION. ELONGATED BERMUDA HIGH WILL ENSURE PLENTY OF LOW LEVEL MOISTURE AND WARMTH WITH THE WEAK GRADIENT ALLOWING SEA BREEZE DEVELOPMENT. HOWEVER THE SEA BREEZE IS LIKELY TO BE THE ONLY FORCING MECHANISM AND IT MAY NOT BE ENOUGH TO OVERCOME THE SUBSIDENCE. A WEAK PIEDMONT TROUGH MAY DEVELOP IN THE AFTERNOON BUT IT PROBABLY WILL NOT BE OF ENOUGH SIGNIFICANCE TO GENERATE CONVECTION. CONTINUED DEEP SOUTHWEST FLOW MON COMBINED WITH WEAKENING MID LEVEL RIDGE WILL LEAD TO AN INCREASE IN PRECIP CHANCES. PRECIPITABLE WATER VALUES CLIMB TO 2 INCHES MON AFTERNOON WITH FORECAST SOUNDINGS SHOWING NO EVIDENCE OF THE PREVIOUS DAYS INVERSION. WEAK SURFACE GRADIENT WILL AGAIN ALLOW FOR SEA BREEZE DEVELOPMENT...WHICH SHOULD BE MORE ACTIVE THAN ON SUN. PIEDMONT TROUGH WILL BE MUCH MORE DEFINED AND SHOULD ALSO ACT AS A FOCUS FOR CONVECTION. WILL CONTINUE TO CARRY AFTERNOON LOW CHC POP. TEMPERATURES WILL RUN ABOVE CLIMO THROUGH THE PERIOD. && .LONG TERM /TUESDAY THROUGH FRIDAY/... AS OF 3 AM SATURDAY...BERMUDA HIGH AND PIEDMONT TROUGH WILL BE THE DOMINANT SURFACE FEATURES WHILE ALOFT WEAK ELONGATED 5H RIDGE EXTENDS ACROSS MUCH OF THE SOUTHERN CONUS. THIS PATTERN IS FAIRLY TYPICAL OF SUMMER AND COMBINED WITH PRECIPITABLE WATER VALUES AROUND 2 INCHES...ALSO TYPICAL FOR THIS TIME OF YEAR...WILL KEEP PRECIP CHANCES NEAR CLIMO THROUGH THE PERIOD...30 TO 40 PERCENT. LACK OF ANY FORCING ALOFT WILL LEAVE THE SEA BREEZE AND PIEDMONT TROUGH AS TRIGGERS FOR CONVECTION. OUTFLOW FROM STORMS AS WELL AS LINGERING BOUNDARIES FROM PREVIOUS DAYS CONVECTION WILL ALSO PLAY POTENTIAL ROLES IN CONVECTIVE INITIATION. LATE IN THE PERIOD A COLD FRONT MAY DROP IN FROM THE NORTH BUT THE STRENGTH OF THIS FEATURE WHEN IT ARRIVES...IF IT ARRIVES...IS QUESTIONABLE. TEMPERATURES WILL BE NEAR TO ABOVE CLIMO THROUGH THE PERIOD. && .AVIATION /07Z SATURDAY THROUGH WEDNESDAY/... AS OF 06Z SATURDAY...EXPECT AREAS OF MVFR/IFR CIGS/VSBYS TO DEVELOP AS LOW LEVEL MOISTURE HAS INCREASED THANKS TO ONSHORE FLOW YESTERDAY. SREF PROBS CONTINUE TO INDICATE THE BEST CHANCES FOR IFR WILL BE INLAND AT KLBT AND KFLO...LIKELY IN THE 09-12Z TIME FRAME. HAVE ALSO ADDED TEMPO IFR FOR KCRE AS SOME FOG/STRATUS IS EXPECTED HERE ONCE THE WINDS GO CALM. WILL MAINTAIN MVFR CONDITIONS AT KILM/KMYR... THOUGH BRIEF PERIODS OF IFR AROUND DAYBREAK CANNOT BE RULED OUT. ALL TAF SITES SHOULD IMPROVE TO VFR BY 13-14Z TODAY. THEN VFR WILL PREVAIL THROUGH THE REST OF THE PERIOD WITH SOUTHEAST WINDS AOB 10 KT...HIGHEST ALONG THE COAST. SLIGHT CHC OF ISOLATED SHRA ALONG THE SEA BREEZE DOES NOT WARRANT A MENTION IN THE TAFS ATTM. EXTENDED OUTLOOK...INCREASING CHANCES FOR AFTN SHOWERS/TSTMS MONDAY THROUGH WEDNESDAY WITH BRIEF AND LOCALIZED PERIODS OF MVFR POSSIBLE. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 645 AM SATURDAY...A PESKY LITTLE BACKDOOR FRONT LOCATED NEAR JACKSONVILLE NC MAY ACTUALLY SNEAK DOWN AS FAR SOUTH AS CAROLINA BEACH BEFORE STALLING LATER THIS MORNING AND RETURNING NORTH THIS AFTERNOON. IT`S A PRETTY INSIGNIFICANT FEATURE IN THE WEATHER-WORLD BUT COULD TURN WIND DIRECTIONS EAST TO NORTHEASTERLY FOR A FEW HOURS. OTHERWISE A LIGHT SOUTHEASTERLY WIND SHOULD PREVAIL THROUGH THE DAY...ENHANCED BY THE AFTERNOON SEABREEZE. ISOLATED SHOWERS OUT ACROSS THE OFFSHORE WATERS WILL MOVE TOWARD THE COAST SHORTLY AFTER SUNRISE. RAINFALL COVERAGE SHOULD AVERAGE ONLY 10-20 PERCENT OF THE AREA...ALTHOUGH UNIDIRECTIONAL WIND THROUGH THE LOWEST 6000 FEET OF THE ATMOSPHERE RAISES THE POTENTIAL THAT WATERSPOUTS COULD DEVELOP EVEN IN A WEAK SHOWER CELL. SHOWER CHANCES SHOULD DIMINISH RAPIDLY THIS AFTERNOON BEHIND THE DEVELOPING SEABREEZE FRONT. WINDS WILL TURN MORE SOUTHERLY WITH TIME TONIGHT WITH NO INCREASE IN WIND SPEED EXPECTED. SEAS CURRENTLY AROUND 2 FEET MAY BUILD TO 3 FEET AWAY FROM SHORE AS A SWELL SET PRODUCED BY THE BERMUDA HIGH ARRIVES AT THE COAST. NOAA BUOY 41002 LOCATED ABOUT 200 MILES OFFSHORE STARTED PICKING UP THIS SWELL ABOUT 6 PM YESTERDAY. THIS SOUTHEASTERLY 7 TO 8 SECOND SWELL SHOULD BE OUR DOMINANT WAVE THROUGH TONIGHT. SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 3 AM SATURDAY...SURFACE GRADIENT WILL REMAIN WEAK THROUGH THE PERIOD WITH ELONGATED BERMUDA HIGH OFF THE COAST. THIS WILL MAINTAIN LIGHT SOUTH TO SOUTHWEST FLOW THROUGH MON NIGHT. SPEEDS WILL RUN AROUND 10 KT OVERNIGHT WITH DIURNAL INCREASES TO A SOLID 15 KT EACH DAY. SEAS WILL RUN 2 TO 3 FT THROUGH THE PERIOD. LONG TERM /TUESDAY THROUGH WEDNESDAY/... AS OF 3 AM SATURDAY...ELONGATED BERMUDA HIGH REMAINS IN PLACE TUE AND WED WITH PIEDMONT TROUGH BECOMING A LITTLE MORE DEFINED. SLIGHT INCREASE IN GRADIENT EACH AFTERNOON WILL INCREASE SOUTHWEST FLOW TO A SOLID 15 KT INTO THE EARLY EVENING HOURS. OTHERWISE SOUTHWEST FLOW WILL BE 10 KT OR LESS. SEAS RUN 2 TO 3 FT.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ NEAR TERM...TRA SHORT TERM...III LONG TERM...III AVIATION...BJR/TRA

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