Area Forecast Discussion
Issued by NWS Wilmington, NC

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596 FXUS62 KILM 241154 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 754 AM EDT WED AUG 24 2016 .SYNOPSIS... High pressure will affect the Carolinas through the end of the week. This will result in dry weather continuing. Humidity will increase by the weekend. An area of low pressure moving through the Bahamas and toward Florida on Sunday will be watched closely for possible tropical development. && .NEAR TERM /THROUGH TONIGHT/... As of 630 AM Wednesday...A 700-500 mb ridge centered along the Gulf Coast will maintain a strong convective cap across the Carolinas today. The subsidence inversion on yesterday evening`s 00z Greensboro, NC sounding was impressive with air temperatures going from +8C at 7300 feet AGL to +12C at 7900 feet AGL. Dry weather is forecast again today as east-northeasterly low-level winds continue around surface high pressure centered off the NJ coast. Only some flat high-based cumulus clouds are expected today at the base of that subsidence inversion. 850 mb temps should range from +14C to +15C this afternoon, sufficient in this dry airmass for highs in the upper 80s to around 90. The high off the Mid-Atlantic coast should weaken, but a ridge axis will continue to extend southwestward across Virginia and into western North Carolina. Since we`re south of this ridge a light northeast wind should continue. Lows should fall into the mid to upper 60s with some lower 70s on the beaches. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 300 AM Wednesday...The 700-500 mb ridge will build eastward Thursday and should be centered over North Carolina on Friday. This will maintain warm and very dry mid and upper level conditions. The low-level airmass will modify a little each day as the tropical ocean water in the western Atlantic feeds heat and moisture into the boundary layer. This should lead to rising temperatures and dewpoints for us as this modified air advects onshore. It`s not impossible that the early morning landbreeze could pop off some shallow convection over the coastal waters Thursday and/or Friday, with the low-level easterly flow perhaps pushing one or two of those ashore. Forecast highs in the 90s will expand Thursday and particularly on Friday due to the warming airmass. Dewpoints rising back toward 70 should add a stickiness we`ve become quite used to this summer, and heat indices Friday afternoon could be in the 94-98 degree range. Overnight lows mainly in the upper 60s Thursday night and lower 70s Friday night. && .LONG TERM /SATURDAY THROUGH TUESDAY/... As of 300 PM Tuesday...At the start of this period the 2 long-term global models, GFS and European, both indicate an Upper High centered overhead, across the NC and SC region. This position basically holds thru Sunday. At the sfc, a weak ridge axis will extend across the region from the ene. This ridging extends from the center of high pressure that was once a 1025+ mb high located just off the NE States today. Mos Guidance indicates Sat will be the warmer day of the 2 days this weekend, with most places seeing 90+ except the immediate coast where onshore flow persists. On Sunday, a weak to modest ne surge occurs. This a result of weak ridging on Sat giving way to ridging from another 1025+ mb high that moves once again across the NE States. Could see isolated convection along the resultant wind boundary Sun but ridging aloft will prevent any further or deeper convection to occur. Highs Sunday will be a degree or 2 lower than Sat highs. For Monday and Tuesday time frame, the 2 global models have their particular solutions for the upper high and associated ridging to maneuver across the Southeast States with its relative positioning to become quite important with respect to the potential for a Tropical Cyclone threat either on the East Coast of the U.S. or the Gulf Coast. For now, Monday and Tuesday will see a decent onshore flow especially in the low levels. If it becomes deep enough, showers may move onshore late at night...followed by low chance for diurnally driven low topped convection over land each day. Will keep POPs at 30 percent or lower this period due to the uncertainty. Temps will run at or a couple degrees below the norm. Wavewatch3 and locally run SWAN models, both respectively indicate the leader swells from Gaston located over the High Seas of the Atlantic at this time period, will begin affecting the local beaches by Midday Sunday. This will result in Moderate to Strong Rip Currents on Sunday across all beaches. Will advertise this in the hazardous weather outlook. && .AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
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As of 12Z...High confidence for VFR through the valid TAF period as high pressure continues to control the current weather pattern. Other than few/sct passing mid clouds, conditions are expected to remain fairly quiet today. Northeast winds around 5 kts will become east-northeasterly this afternoon up to 10 kts. Tonight, winds become light and variable with nearly clear skies through Thursday morning. EXTENDED OUTLOOK...Potential for MVFR due to areas of fog early Friday and with isolated convection on Sunday. Otherwise expect VFR.
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&& .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 630 AM Wednesday...Surface high pressure is centered a couple hundred miles off the New Jersey coast. The high will move slowly eastward today and tonight, but a ridge axis will continue to extend southwestward across Virginia and into western North Carolina. Surface pressures across the northern Bahamas and Florida are fairly low, and this difference in pressure will maintain an east-northeasterly wind across the Carolina coastal waters. Wind speeds of 15 kt this morning should diminish to 10-15 kt this afternoon. Seas have been churned up by the wind over the past 8-12 hours and buoy reports at 6 AM include 4.3 feet 5 miles SE of Wrightsville Beach and 4.6 feet at Frying Pan Shoals. These areas of 4+ foot seas should die away by noon with 2-3 foot seas anticipated for the afternoon into tonight. SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 300 AM Wednesday...High pressure along 40 degrees latitude will continue to weaken Thursday and Friday even as a ridge axis extends southwestward across Virginia and western North Carolina. As the pressure gradient decays between the weakening high and lower pressures present across the Bahamas and Florence, wind speeds should diminish to around 10 knots by Thursday night into Friday. Winds this light would normally equate to 2 foot seas, however we`ll begin to pick up a long period east-southeast swell from at least one and perhaps two tropical systems in the Atlantic. This should create combined sea heights of 3 feet to locally 4 feet by Friday. LONG TERM /SATURDAY THROUGH SUNDAY/... As of 300 AM Wednesday...Weak Sfc ridging from the ene on Saturday will produce a 10 to 15 kt ene wind across the area waters. Wind driven waves or even a pseudo ground swell will dominate the significant seas with 3 to 4 ft common with a few 5 footers possible, with periods in the 6 to 8 second period range. For Sunday, the sfc ridging re-positions to a "new" center of high pressure moving across the NE States. The sfc pg does increase, resulting in NE winds at a solid 15 kt possibly up to 20 kt. The 2 to 4 foot pseudo ground swell at 6 to 8 second periods, will become mixed with the easterly leader swells from Gaston running at 13 to 16 second periods. Wavewatch3 and locally run SWAN models, both respectively indicate the leader swells from Gaston, located over the High Seas of the Atlantic at this time period, will begin affecting the local waters by midday Sunday and continuing there-after. The combined pseudo ground swell and leader swells from Gaston, could reach SCA thresholds during the aftn and night. Will advertise this in the hazardous weather outlook. && .CLIMATE... As of 300 AM Wednesday...Shortly before 2 AM this morning Wilmington`s official temperature here at the airport touched 69 degrees. This ends the streak of consecutive days with low temps 70 degrees or warmer at 58, now the all-time longest streak in Wilmington history dating back to 1874. Wilmington`s Consecutive Days with Low Temperatures 70+ degrees #1 58 days 6/27/2016 to 8/23/2016 #2 56 days 6/29/2012 to 8/23/2012 #3 52 days 6/22/1941 to 8/12/1941 #4 48 days 7/ 6/1986 to 8/22/1986 #5 46 days 6/28/1991 to 8/12/1991 Yesterday morning the streak of consecutive 70+ low temps in Florence was broken at 62 days. This is also an all-time record for Florence dating back to 1948. Florence`s Consecutive Days with Low Temperatures 70+ degrees #1 62 days 6/22/2016 to 8/22/2016 #2 60 days 6/26/2005 to 8/24/2005 #3 55 days 7/ 6/1975 to 8/29/1975 #4 46 days 7/10/2010 to 8/24/2010 #5 45 days 6/11/2015 to 7/25/2012 #5 45 days 6/28/1991 to 8/11/1991 From a climate perspective, the summer of 2016 has been interesting in that daily highs and lows have been among the warmest average readings in history without having any individually extremely hot days. In Wilmington since June 1st our average high temperature is the fifth hottest in history and average low temperature is the third hottest, but the highest temperature this summer of only 98 degrees was not exceptional at all. Florence since June 1st has had its seventh hottest average daily high temp, record hottest daily low temp, but the highest temperature of the summer at 98 degrees is actually cooler than the "normal" hottest annual temp of 101. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...TRA NEAR TERM...TRA SHORT TERM...TRA LONG TERM...DCH AVIATION...SGL CLIMATE...TRA is the U.S. government's official web portal to all federal, state and local government web resources and services.