Area Forecast Discussion
Issued by NWS Wilmington, NC

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805 FXUS62 KILM 291012 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 612 AM EDT Thu Sep 29 2016 .SYNOPSIS... A cold front approaching from the west will slow down on Friday and linger near or along the Carolina coast through this weekend. High pressure will build in behind the front through early next week. && .NEAR TERM /THROUGH TONIGHT/... As of 600 AM Thursday...Have upped the POPs across the northernportions of the FA to account for the persistent convection and alsoto account for its very slow movement eastward with time. The QPFhas been updated and increased across the aforementioned areas thatwill see POPs raised. As of 330 am Thursday...SPC has a good portion of the ILM CWA...mainly away from the immediate coast...in a marginal risk today into this evening. The cutoff low is progged to drop to central Kentucky by Friday morning. Models indicate that this will be its furthest southern push. Dynamics associated with mid-level vorts or s/w trofs, interacting with the sfc cold front now across the central Carolinas, and rotating around this upper low further aid the development and persistence of convection today. Persistence, meaning even after the days insolation has ceased the convection will continue. This illustrated well by the convection that has persisted across central NC during these pre-dawn Thu hours. In general, have peaked POPs at 50 percent. But, depending on where the current convection continues at xmit time, may go hier to likely then drop it back down later this morning. POPs have been continued along the immediate ILM CWA coast during the pre-dawn Fri hrs due to convection aided by an upper s/w trof tracking nearly due north around the periphery of the cutoff low. The nocturnal development of convection over the Atl waters this time of the year will also play a part. As for temps, the European and NAM MOS Guidance, both have been doing well with daytime highs based on the latest verification stats for the local area for the past several days. For night time Lows, the NAM Mos alone, is verifying the best. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... As of 345 AM Thursday...To no surprise, the cutoff upper low and mid-level vorts, like spokes on a bicycle tire, rotating around it will be the driver of the sensible weather across the ILM CWA this period. The good news, models have this cutoff/closed low slowly opening up and lifting northward by the end of this period as a result of the strong westerlies now able to move this upper feature. At the sfc, the cold front will slowly make some progress to the coast on Friday and on Saturday it basically stalls either along the immediate coast or just offshore due to it becoming parallel with the flow aloft. Therefore POPs will be confined along the eastern 1/3rd of the ILM CWA and the adjacent Atlantic waters thruout this period. The dry slot or tongue will affect mainly the western 2/3rds of the ILM CWA helping to eliminate POPs in that area. Could see hier POPs during the pre- dawn hrs along the immediate coast during the pre- dawn Sat and Sun hours due to the combined nocturnal development over the waters and any mid- level vorts having either rotated around the cutoff low or picked up off the Florida west coast or the northern Bahamas. Max/Min temps to remain above normal, 1 to 2 categories, thruout this period. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... As of 3 AM Thursday...Large upper low finally lifting out to the northeast early in the period. In its wake will be a weak pressure gradient and a dissipating frontal boundary just offshore. A few showers along this front may affect coastal locales but suspect that most areas stay rain-free and seasonable. As the upper low begins to interact with troughiness east of Canada rising surface pressures advect into the eastern U.S. Tuesday and Wednesday. Should this flow be NE then some lower dewpoints may creep into the Carolinas but current progs show more ENE and likely preclude that. Building heights aloft argue for not much in the way of meaningful precip though a few sprinkles tough to rule out in the onshore low level flow. This gradient could become pinched by Matthew and it may become breezy locally by Wednesday if the quick GFS is correct. && .AVIATION /10Z THURSDAY THROUGH MONDAY/... As of 06Z...Rather persistent storms just west of our area and the HRRR wants to spread them all the way to the coast by daybreak. This seems ambitious but have covered for this possibility with VC. Better chance for predominant rain is at FLO and LBT. Then there may be a break in the action before daytime heating causes isolated storms to fire through the day as front remains stalled to our west. By evening a large scale dry slot should be spreading into the area shutting down any rainfall from SW to NE though a few may linger at the coast. EXTENDED OUTLOOK...Primarily VFR. Isolated to scattered afternoon showers through much the period, although limited in strength and coverage due to dry air aloft. && .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 605 AM Thursday...The sfc cold front to remain inland from the coast during this period. That means a southerly wind will continue across the local waters thruout this period. The sfc pg to remain semi-tightened ahead of the cold front and should produce 10 to 15 kt wind speeds...and could see occasional gusts up to 20 kt, especially during the overnight period. Significant seas will run a solid 3 foot. The spectral density charts indicate that a pseudo easterly swell at 7 second periods, with an occasional ese swell at 10 second periods, will both dominate the seas spectrum. Wind driven waves will mesh on top of this e to ese ground swell. Convection this morning will move across the local waters, mainlybetween Little River Inlet and Surf City. SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... As of 400 AM Thursday...The movement of the cold front at a snail`s pace will push it to the coast late Friday and possibly either across the coastal waters or just offshore from Carolina coastlines. The sfc pressure pattern will result in a S to SW wind direction thruout this period. The sfc pg will remain semi-tightened east of the cold front, with 10 to 15 kt speeds, and somewhat relaxed in the vicinity of the cold front, with 10 kt or less speeds. Significant seas to continue at 2 to 3 ft thruout this period. The ese ground swell at 7 to 9 second periods will mainly dominate the seas with local wind driven waves at 3 to 4 seconds on top. Expect convection thruout this period, with the pre-dawn hrs thru daytime morning hrs of each day exhibiting the hier pops during this period. LONG TERM/SUNDAY THROUGH MONDAY/... As of 3 AM Thursday...Weakening front along the coast Sunday will keep winds very light though there is some uncertainty regarding direction-though primarily onshore. Small wind chop combine w ESE swell for a 2 to 3 ft dominant wave height. No significant changes noted heading into Monday. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...MBB NEAR TERM...DCH SHORT TERM...DCH LONG TERM...MBB AVIATION...MBB/MRR

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