Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 151643 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 1143 AM EST Fri Dec 15 2017 .SYNOPSIS... Seasonable and fair weather will continue through the weekend, with a dry cold frontal passage expected late today followed by high pressure. Southerly winds and a warming trend will begin Sunday and last through Tuesday evening ahead of a cold front, with a chance of rain Monday and Tuesday. A cooler and drier air mass will overspread the area mid-week in wake of the cold front. Another cold front will approach the coast next Friday, potentially creating a wet start to next weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 930 AM Friday...Slow moving cold front still bisecting the area. 12Z MHX RAOB shows a pretty dry column save for a moist layer around 16kft...not a good setup for front-related precipitation. Pair this with only weak vort centers found within the low amplitude mid level flow and expect little other than a windshift with FROPA as some cooler air begins to filter into the region overnight. As of 300 AM Friday...Area of low pressure was developing along weak cold front draped from west to east across the local forecast area early this morning. This low will deepen slightly over the Cape Fear coast this morning before lifting off to the NE into the waters off the Delmarva coast by this evening. Winds will be variable at times with a more northerly flow to the north side of front and SW to the south. Overall light to calm winds this morning will pick up out of the west on the back end of the wave of low pressure through today. Deep mid to upper trough extending down from the Great Lakes connects back to cutoff low over Baja California. Westerly flow aloft will stream this associated mid to upper level moisture across the Southeast through today. Sounding data and moisture profiles show decent layer of moisture at times between 15k and 25k and therefore expect periods of mid to high clouds to continue to stream across the area through today. Otherwise not expecting any pcp from the weak system. As low lifts off to the northeast, the cold front will push south and east as high pressure builds in behind it late today through tonight. The mid to upper trough should also push far enough south to displace most of the higher clouds away from the local forecast area. Overall expect sunshine to be filtered out by mid to high clouds through today with deep westerly downslope flow. A cool start to the morning will be followed by a nice warmup with temps reaching near or above 60 degrees. By tonight skies will clear with some drier and cooler air moving in behind front. Expect temps to drop down to the low to mid 30s. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... As of 300 AM Friday...Longwave upper pattern not yet established during this period. Split jet stream with the northern branch retreating back northward with time and the southern branch extending northward. During this same time period, an upper ridge will amplify and begin to affect the local FA by Sunday with the upper ridge axis extending from the Bahamas north to eastern NC by the end of this period. At the sfc, center of high pressure will park itself across the ILM CWA and adjacent waters Sat thru early Sunday then drift east and offshore by Sunday night. With subsidence overhead, clouds will basically be non-existent other than thin jetstream cirrus Sat thru early Sun morning. With the expanding south to north upper ridge axis across to just east of the FA by the end of this period, additional clouds will basically begin to override the ridge axis. Looking at mainly opaque high level clouds early Sunday and eventually mid-level clouds by Sunday night. Looking at low clouds expanding across the FA as illustrated by various model RH Time Height displays for locations across the FA. Have delayed the arrival of stratiform light rain to the pre-dawn Monday hrs. As for temps, at or a category below normal temps for Sat. Decent rad cooling conditions Sat night/Early Sun will drop lows to around the freezing mark with upper 30s to around 40 for the immediate coast. Looking at a nice warm-up Sunday with return flow from the high sliding off the Carolina coasts. Highs will be a good 5 to 10 degrees milder than Sat progged highs with weak WAA occurring. Sun night will see clouds and threat of pcpn keep lows elevated, running a good 10 degrees above the norms. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 300 PM Thursday...Primary caption this period, `Milder with Rain Chances Early Next Week`. Highly amplified troughing trend in the Baja and SW desert will cause expansion northward of the the Bahamian/FL upper ridge. Concurrently, surface high pressure centered offshore of the Carolinas, will help to complete the noteworthy warm-up, circulating milder air in southerly flow. Robust moisture advection will ensue as lower tropospheric winds tap Gulf air. Two time periods encapsulated by this moisture in deep column lift occur Monday, and again late Tuesday. Monday a jet-streak entrance region appears aligned to provide support aloft, with frontal convergence coming into play Tuesday. The period Monday and Tuesday offer rain chances, although a high uncertainty prevails on how much. Drying/cooling Wednesday in wake of the front, but return flow quick on the heels, by THU night ahead of another approaching cold front. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
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As of 18Z...VFR through the TAF period. A deep westerly flow will continue to stream mid to high clouds across the area. Surface winds will be SW-W around 10 kts. Winds will veer to the WNW as a weak front drops south through the terminals late this afternoon and early evening. As the front moves farther south and high pressure builds in, winds will become light north aob 3 kt with mid clouds decreasing. After sunrise winds will be light NW-NE becoming SW by the end of the TAF valid period. Extended Outlook...VFR. VFR tempo MVFR/SHRA Monday through Tuesday night.
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&& .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 930 AM Friday...No changes to the forecast anticipated at this time. Will be monitoring for the potential for gusts to 25 kts as low level wind fields tighten. At this time however it appears that weak lapse rates should preclude them being frequent enough to warrant any headlines. As of 300 AM Friday...Generally quiet marine conditions early this morning will rebound later today. Low pressure will deepen as it moves off to the northeast dragging front south and east of forecast area. Light SW to W winds less than 10 kts will increase up to 15 to 20 kts briefly as they veer around to the W to NW this afternoon into early evening as front pushes south and east. Seas 2 to 4 ft will jump up to 3 to 5 ft for a brief period toward evening before dropping back down after midnight as winds shift north and begin to diminish. SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... As of 300 AM Friday...Marine conditions will be good for boaters venturing into the local Atlantic waters. It will be on the cool side with temps limited by local SSTS in the 50s. Center of high pressure will be overhead Sat then sliding slowly east to the offshore waters by Sun night. Variable winds less than 10 kt will occur during Sat followed by return flow around the departing high providing SE to S 10 kt Sun and SSW 10 to 15 kt Sun night. Light Rain chances will increase to low chance late Sun night. Significant seas will subside to less than 2 ft during Sat as input from locally produced wind waves decreases. This will leave a dominating 1 to 1.5 foot easterly ground swell at 10 second periods Sat night thru Sunday. Wind waves will increase Sun night but the small ground swell will remain dominant. LONG TERM /SUNDAY THROUGH TUESDAY/... As of 300 PM Thursday...Marine conditions will gradually worsen into early next week, as a cold front approaches, then crosses the coast late Tuesday night or early on Wednesday. Small Craft Conditions appear to be approached sometime on Tuesday, by evening, in blustery SW wind of 20 KT and gusty, and 5 foot seas offshore. Conditions inshore will not be as bad, due to cooler waters. Rain showers may reduce visibilities at times Monday through Tuesday night. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ NEAR TERM...RGZ SHORT TERM...DCH LONG TERM...MJC AVIATION...MRR

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