Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 300723 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 323 AM EDT SUN AUG 30 2015 .SYNOPSIS... MOISTURE FROM THE GULF OF MEXICO WILL BRING INCREASING COVERAGE OF SHOWERS AND ISOLATED THUNDERSTORMS FOR THE UPCOMING WEEK. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1030 PM SATURDAY...INFRARED SATELLITE IMAGERY SHOWS THE HIGH LEVEL STREAM OF MOISTURE CONTINUES FROM THE SOUTH...WHILE AIRPORT ASOS/AWOS OBS SHOW THE 3000-FOOT CLOUD DECK CONTINUES ALONG THE GRAND STRAND AND AS FAR NORTH AS SOUTHPORT. TEMPERATURES ARE FALLING INLINE WITH THE UPDATE EARLIER THIS EVENING AND ONLY A FEW TWEAKS ARE NEEDED TO THE FORECAST. DISCUSSION FROM 730 PM FOLLOWS... MULTILAYERED CLOUDS ACROSS THE AREA ARE IN AT LEAST THREE DISTINCT GROUPS: SCATTERED 3000 FOOT CLOUDS WHERE MARINE MOISTURE EXISTS...SCATTERED 6000 FOOT CLOUDS AT THE TOP OF THE DEEPER MIXED LAYER...AND BROKEN 18000-30000 FOOT CLOUDS IN A VERY MOIST SOUTH- SOUTHWEST FLOW ALOFT. THIS MOIST FLOW ALOFT IS KEY TO OUR FORECAST OVER THE NEXT 12 HOURS AS IT WILL DEEPEN AND EVENTUALLY LEAD TO SHOWERS CROSSING THE SANTEE RIVER INTO NORTHEASTERN SOUTH CAROLINA. UNTIL THEN...PARTLY CLOUDY SKIES SHOULD TURN MOSTLY CLOUDY LATE. VERY FEW CHANGES WERE NEEDED TO THE FORECAST WITH THIS EARLY-EVENING UPDATE. DISCUSSION FROM 330 PM FOLLOWS... UNUSUALLY STRONG UPPER LOW OVER THE NE/NORTH-CENTRAL GOMEX TO WEAKEN AND START MOVING ASHORE IN FL PANHANDLE THROUGH THE PERIOD. MOISTURE WILL THUS OVERSPREAD THE AREA FROM SW TO NE AND BE MOST PRONOUNCED AT THE MID LEVELS. LOW LEVEL WILL LAG BEHIND BUT SHOULD STILL KICK IN OVER SOUTHERN ZONES. SOME RAIN CHANCES WILL THUS RAMP UP LATE TONIGHT OVER FAR SOUTHERN COUNTIES. IN THE VERY NEAR TERM SOME MOISTURE MOVING OUT OF CHS CWA APPEARS TO BE DISSIPATING BEFORE REACHING THE GROUND DUE TO LIGHT FORCING AND LARGE DEWPOINT DEPRESSIONS. AS THE NIGHT WEARS ON A STRENGTHENING OF THE LIFT AND LESSENING OF THE DEWPOINT WILL FAVOR SOME LIGHT RAIN BY THE END OF THE PERIOD OVER ROUGHLY THE SOUTHERN HALF OF THE CWA. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... AS OF 315 AM SUNDAY...SHAPING UP TO BE A RATHER UNSETTLED COUPLE OF DAYS AS THE STREAM OF MOISTURE AS SEEN ON INFRARED IMAGERY EXTENDING DEEP INTO THE TROPICS CONTINUES TO MOVE ACROSS. I HAVE ELEVATED POPS MAINLY FOR MONDAY TO LIKELY ALONG THE COAST WHERE THE DEEPEST MOISTURE WILL RESIDE. SOME DRYING IS NOTED IN THE PROFILES FOR TUESDAY MAINLY IN THE GFS BUT THE NAM REMAINS BULLISH ON POPS. TO COMPROMISE I DID DECREASE THE POPS SOMEWHAT TUESDAY BUT STILL ADVERTISING CHANCE VALUES AREA WIDE. I TRIMMED BACK EXPECTED HIGHS A DEGREE OR TWO MONDAY AND INCREASED THE MORNING LOWS THE SAME DUE TO THE EXPECTED MOISTURE. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... AS OF 315 AM SUNDAY...MEDIUM RANGE GUIDANCE CONTINUES TO DEPICT A WEAK PATTERN BOTH AT THE SURFACE AND ALOFT. THERE REMAINS AMPLE MOISTURE TO GENERATE CONVECTION AND WITH A SUBTLE PIEDMONT TROUGH AND COASTAL TROUGH FROM TIME TO TIME...PRUDENT TO KEEP GOOD CHANCE POPS IN THE FORECAST THROUGH FRIDAY. MODELS DO HINT AT A BACKDOOR FRONT SLIDING THROUGH SATURDAY WHICH WOULD DRY THINGS OUT. THIS TREND IS REFLECTED IN THE FORECAST WITH LOWER POPS AND SLIGHTLY LOWER TEMPERATURES. && .AVIATION /07Z SUNDAY THROUGH THURSDAY/... AS OF 05Z...EXPECT VFR THROUGH THE VALID 06Z ISSUANCE PERIOD...WITH INCREASING CLOUD COVER AT ALL LEVELS EARLY THIS AM THROUGH MIDNIGHT MONDAY. PATCHY MVFR DURING THE PRE-DAWN SUN HRS FROM GROUND FOG REMAINS POSSIBLE. ISOLATED/SCATTERED -SHRA POSSIBLE THIS SUN AFTN AND EVENING. VFR WILL PREVAIL THROUGH OVERNIGHT WITH LIGHT WINDS AND SOME LINGERING LOW CLOUDS 2-3K FT ACROSS THE NE SOUTH CAROLINA AREA EARLY ON. SATELLITE IMAGERY VIA WATER VAPOR AND IR CHANNELS... CONTINUE TO DEPICT A GRADUAL INCREASING TREND OF MAINLY MID TO HIGH LEVEL CLOUDS ACROSS THE AREA. EXPECT THIS TREND TO CONTINUE THRUOUT THE VALID FORECAST ISSUANCE PERIOD AS VARIOUS MODEL FCST SOUNDINGS SUPPORT INCREASING MOISTURE INTO THE AREA. BKN/OVC MID-HIGH LEVEL CLOUDS BECOMING COMMON THRUOUT THE FCST PERIOD. SOME GUIDANCE DOES SUGGEST POSSIBLE BKN LOW CIGS WHICH COULD CREATE MVFR TOWARDS DAYBREAK SUN MORNING...BUT CONFIDENCE IS LOW...THUS HAVE NOT INTRODUCED IN GOING FCST. AFTER DAYBREAK...ANTICIPATE LOWERING CLOUD HEIGHTS THRUOUT THE DAY WITH DIURNALLY INDUCED CU/SC ADDING TO THE CLOUD SPECTRUM. HAVE STAYED CLOSER TO THE DRIER GFS BIAS FOR LOWER PCPN CHANCES AND COVERAGE...AND ALSO A SLOWER LOWERING OF CEILINGS DURING THE DAYTIME AND EVENING SUN HOURS. THUS...WILL INDICATE VCNTY SHRA AND HOLD OFF WITH THUNDER FOR THIS 06Z PACKAGE AT ALL SITES. WINDS AT THE 06Z INITIAL TIME WILL EITHER START OUT WITH CALM INLAND...TO NE 2 TO 4 KT AT THE COAST...BECOMING NE 4 TO 8 KT DURING DAYTIME SUN MORNING AT ALL SITES. LOOK FOR FURTHER VEERING TO E-SE AT 5 TO 10 KT DURING SUN AFTN AND EARLY EVENING...DROPPING TO LESS THAN 5 KT BY MID TO LATE SUN EVENING. EXTENDED OUTLOOK...PREDOMINATELY VFR WITH MVFR/IFR CONDITIONS FROM ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS THROUGH THE EXTENDED. BRIEF MVFR/IFR MORNING FOG/STRATUS IS ALSO EXPECTED EACH DAY. && .MARINE... NEAR TERM /THROUGH TONIGHT/...AS OF 1030 PM SATURDAY...WIND DIRECTIONS ARE FROM THE NE OFFSHORE BUT VEER MORE EASTERLY AT THE BEACHES. WITH THE EXCEPTION OF THE 18Z NAM ALL MODELS SHOW WINDS BACKING TO THE NE EVEN ALONG THE COAST OVERNIGHT. VERY FEW CHANGES WERE NEEDED TO THE FORECAST WITH THIS EARLY-EVENING UPDATE. DISCUSSION FROM 330 PM FOLLOWS... DROPPED THE SCEC A BIT EARLY AS SEAS HAVE DECREASED TO 3 FT AT NEAR SHORE BUOY 41110 AND 4.5 FT ALL THE WAY OUT AT FRYING PAN SHOALS BUOY 41035. CONDITIONS ARE STILL QUITE CHOPPY WITH EVEN THE LATTER BUOY SHOWING A WAVE POWER PEAK AT JUST 5 SECONDS. THE HIGH TO OUR NORTH IS FORECAST TO WEAKEN THIS EVENING AND THE LOCAL GRADIENT AND RESULTING WINDS WILL DO THE SAME. SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... AS OF 325 AM SUNDAY...IT APPEARS THE STRONGEST WINDS WILL OCCUR EARLY MONDAY AS GOOD MID LEVEL FORCING LEADS TO THE DEVELOPMENT OF A COASTAL TROUGH. SHOULD SEE SOUTHEAST WINDS OF 10-15 KNOTS FOR A FEW HOURS. THIS TROUGH MOVES INLAND WITH THE SEA BREEZE AND BASICALLY DISSIPATES EARLY TUESDAY. IN ITS WAKE WEAK WINDS OF TEN KNOTS OR LESS DEVELOP WITH THE DIRECTIONS MAINLY DICTATED BY THE LAND AND SEA BREEZES. SEAS WILL SEE A BRIEF PERIOD OF 2-4 FEET MONDAY MORNING AND TREND DOWNWARD SLIGHTLY THEREAFTER. LONG TERM /WEDNESDAY THROUGH THURSDAY/... AS OF 325 AM SUNDAY...VERY LITTLE IN THE WAY SYNOPTICALLY TO SHOW ANY DEVIATION FROM THE STANDARD SUMMERTIME PATTERN OF WEAK SOUTHEAST WINDS AND SEAS OF 2-4 FEET. SOME CONVECTION COULD BRIEFLY DISTORT THESE FIELDS OCCASIONALLY BUT THESE SHOULD HOLD FOR THE MOST PART. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ SYNOPSIS...SHK NEAR TERM...DCH/TRA SHORT TERM...SHK LONG TERM...SHK AVIATION...DCH/SGL

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