Area Forecast Discussion
Issued by NWS Wilmington, NC

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814 FXUS62 KILM 250536 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 136 AM EDT Sun Sep 25 2016 .SYNOPSIS... A backdoor cold front will come through early Sunday but it may stall close enough to keep the weather unsettled into early next week. A stronger cold front arrives Tuesday night into Wednesday with some drying and cooling beginning Thursday. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... As of 1030 PM Saturday...No changes to the forecast with the latest update. Previous discussion follows: Tropical moisture surrounding a very persistent low pressure area finally moved south of the area last night, allowing drier weather to build in from the north. We`ve got shallow cumulus near the coast south of Cape Fear due to residual low-level moisture, however a subsidence inversion around 5500 feet AGL is keeping the lid of these clouds. Convective inhibition (CIN) as large as 60 J/kg is expected to be unbreakable by the weak seabreeze, leaving us with a dry forecast this evening into tonight. A cold front moving quickly southward through Virginia should reach the eastern Carolinas between 5-10 AM Sunday. Although the front is now currently outlined by fairly dense low clouds, increasingly dry air in the 925-850 mb layer should erode a good deal of these clouds as the boundary moves south. Light winds and clear skies ahead of the front should allow patchy fog to develop late tonight. Lows mainly upper 60s with some lower 70s on the beaches. && .SHORT TERM /6 AM THIS MORNING THROUGH MONDAY NIGHT/... As of 300 PM Saturday...High pressure dropping southeastward across the eastern Great Lakes will push the cold front through the area Sunday morning. Behind this front, northeasterly winds will push heavily modified Canadian air into the eastern Carolinas. This air will have spent the past 400-500 miles traversing the very warm western Atlantic Ocean and will have picked up a good deal of moisture. Throw in some sunshine and steep low-level lapse rates and scattered showers and t-storms should develop Sunday afternoon. Forecast PoPs are as high as 40 percent centered on the Burgaw- Whiteville-Marion corridor where it appears a mesoscale area of low- level convergence may develop due to the proximity of the front and the shape of the coastline from Cape Lookout to Myrtle Beach. As the high moves across New England Sunday night and into the Atlantic Monday afternoon, our northeasterly low-level flow will gradually turn easterly, perhaps even southeasterly Monday night. These onshore winds will advect in enough moisture to support 20-30 percent chances of showers, most numerous across South Carolina. Ridging aloft should keep these showers from becoming too numerous, however it`s interesting to note that both the 12z ECMWF and 12z GFS bring a mid-level wave across the area Monday night that could enhance the potential of showers. I`ve bumped PoPs up a bit for that potential. && .LONG TERM /TUESDAY THROUGH SATURDAY/... As of 300 PM Saturday...Showers and isolated thunderstorms are looking more and more likely on Tuesday. Cold front will be heading our way and accompanied by decent height falls aloft. The main factor arguing against precip being the position of the upper low leading to westerly flow aloft locally. Despite this models in pretty good agreement with some coverage of storms. Energy diving into the western part of the mid level trough will slow the surface boundary and there may even be a wave that develops just off the coast for a continuation of rain chances into Wednesday especially along the coast. Then strong dry advection and moderately strong cool advection Wednesday night into Thursday. A cooler early Fall airmass expected to round out the long term. && .AVIATION /06Z SUNDAY THROUGH THURSDAY/...
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As of 06Z...Back door cold front approaching from the NE will drop slowly SW overnight, bringing increasing stratus to the terminals. LBT/ILM are most likely to experience stratus overnight, with short duration IFR expected before becoming predominantly MVFR through daybreak. The SC terminals will have FROPA after dawn, so only some sct stratus is expected. However, all terminals have a chance for some fog ahead of this back door front, and a few sites have already dropped to MVFR around the area. Best chance for IFR fog is at CRE, but the inland terminals may also see IFR vsbys towards daybreak. Winds will be calm, becoming light from the NE late. After daybreak, fog/stratus will lift but the cold front will stall, likely across SC. This will create a chance for showers through the day at all terminals, but attm no thunderstorms are expected. Winds will become E/NE around 10 kts, and VFR is forecast with any restrictions confined to tempo MVFR in showers. More stratus is possible Sunday night, and have reintroduced MVFR at all terminals at the end of the valid period. EXTENDED OUTLOOK...Chance for SHRA/TSRA Tue through Wed. Otherwise expect VFR.
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&& .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 1030 PM Saturday...No changes to the forecast with the latest update. Previous discussion follows: A cold front currently moving south through Virginia should reach the Cape Fear to Cape Romain area between 5-10 AM Sunday morning. Out ahead of the front we expect northeast winds 10 knot or less to continue. The front will come through dry but should result in increasing northeasterly winds, most noticeable during the day Sunday. Area buoys are reporting anywhere from 1 foot seas just off Sunset Beach to 3 foot seas near and east of Cape Fear. Seas consist of a mix of 10-second easterly swell from Tropical Storm Karl out near Bermuda, and local wind waves averaging 4-second period. Karl`s swell may build by another 0.5 to 1.0 foot by late tonight, mainly realized in the waters north & east of Frying Pan Shoals. SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 300 PM Saturday...High pressure moving eastward across the Great Lakes and into New England Sunday will drop a cold front across the area Sunday morning. Behind this front, northeasterly winds will strengthen to a solid 15 knots with some gusts near 20 knots expected Sunday afternoon into Sunday night. The high will move off of the New England coast Monday afternoon, allowing our winds to gradually turn easterly, then southeasterly Monday night. Karl`s 10-second easterly swell will remain with us through Sunday. When combined with a shorter period wind chop, combined seas of 3-4 ft are expected Sunday, diminishing to 2-3 feet Monday. LONG TERM/TUESDAY THROUGH THURSDAY/... As of 300 PM Saturday...Prefrontal southerly winds develop on Tuesday after possibly starting the day light southeasterly. Not much of a wind increase as the day wears on due to the approaching front now a bit slower. Its passage late Tuesday night may be followed by its stalling just off the coast so the wind and seas forecast is a bit muddled beyond Tuesday night. The 00z ECWMF didn`t even have FROPA until Wednesday night. Despite the uncertainties there still seems to be no big cool push (that might necessitate some headlines) during the period-but there may be just beyond. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...MBB NEAR TERM...REK/RJD SHORT TERM...TRA LONG TERM...MBB AVIATION...JDW MARINE...REK/RJD/TRA/MBB

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