Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 180620 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 116 AM EST Sun Feb 18 2018 .SYNOPSIS...
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High pressure will build down from the north pushing a cold front south and east through this morning. This front will return back to the north, through the area, as a warm front early Monday. Bermuda High pressure will follow and provide several days of possible record warmth through mid week. A cold front may drop far enough south to bring a slight cool down for Friday, but warm weather will return for next weekend. .NEAR TERM /THROUGH SUNDAY/... As of 1000 PM Saturday...Quick changes with the addition of patchy fog across all locations based on latest sfc obs trends. Sfc dewpoints are progged to increase into the 50s which is not high enough for sea fog to develop when passing across SSTs that are now in the mid to upper 50s. Enough low level moisture will advect inland with both stratus and patchy ground fog possible. The low temps for tonight will basically occur by late this evening, and then slowly increase due to WAA from SE to S flow. Did not change any POPs. Have kept the previous pcpn type and coverage and continued with low QPF ie. less than 0.05 inches. Previous....................................................... As of 300 PM Saturday...Front that was stalled south of the area has begun lifting back north as a warm front. Weak surface wave moving northeast along the boundary is helping lift the front back into the forecast area. Shallow layer of near saturation, from roughly 2k ft to 6k ft, is starting to show up as echos on KLTX. Thus far rain is not being reported in any locations. As the front returns north this evening there will be a narrow window where the layer below 6k ft will be nearly saturated. However, the lack of forcing coupled with the short duration of the event suggests a low chance of measurable rainfall. Cannot rule out a few areas measuring a hundredth to two this evening into tonight but suspect most of what falls from the sky will lead to dampness with only a few areas ending up wet. Still this is likely to be the best chance for measurable rainfall during the period. Front`s northward progression is limited and short- lived. The surface wave moves off to the northeast this evening, opening the door for the return of high pressure. The north winds on the backside of the exiting low coupled with northerly flow around the east side of the building high helps drive the front to the south in the pre- dawn hours. Low tonight will once again hinge upon how quickly the cooler air arrives. Warmer solution worked out better this morning and is likely to be the way to go tomorrow morning as well. Lows will range from upper 40s to lower 50s. Front pushes well south of the area tomorrow morning, aided by stretched shortwave pushing off the coast late tonight. High pressure builds in from the northwest and quickly shifts east, a result of the flat flow aloft. Forecast area will experience significant low level drying and skies are likely to be partly to mostly sunny tomorrow. Despite light northeast flow, becoming onshore in the afternoon, the abundance of sunshine coupled with limited cold advection results in highs above climo. Away from the immediate coast highs will be in the mid 60s, with highs at the coast likely to be mid to upper 50s. Any rain chances end with the passing of the front and tomorrow will be dry.
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&& .SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/... As of 300 PM Saturday...A cloudy yet warming period on tap for the short term. Warm front lifting through late Sunday night into Monday morning to yield warm and moist advection. Ascent will be very sloped and gentle though so rainfall chances will remain very low and QPF prospects negligible. Mid level ridge starts building into the area from offshore late Monday night helping to start decreasing cloud cover. && .LONG TERM /TUESDAY THROUGH SATURDAY/... As of 300 PM Saturday...An exceptionally strong upper level ridge is expected to develop next week off the East Coast. 500 mb heights up to 591 dam would be above normal in August, and should be among the highest values ever observed locally this early in the season according to the SPC sounding climatology webpage. The Penn State GEFS ensemble viewer (http:/cms.met.psu.edu/sref/GEFS) shows 500 mb height forecasts nearly 3 standard deviations above normal for several days next week. This should be a vertically stacked high with deep southerly flow transporting an unseasonably warm and humid subtropical airmass across the Carolinas. High temperatures are expected to reach 80-83 degrees Tuesday through Thursday inland, with somewhat cooler readings expected near the coast due to nearshore water temperatures still in the 50s. The warmest days are expected to be Wednesday and Thursday where record highs are currently forecast in Florence and Wilmington. Thursday should be the warmest day near the coast as an upper level trough passes through New England, veering surface winds a bit more westerly which will delay/suppress the seabreeze and its cooler, maritime influence. I think Thursday may have the best potential for Myrtle Beach to achieve a record high. As the trough passes through New England and Canadian high pressure advances eastward across the Great Lakes, a backdoor cold front will get shoved southward into the Carolinas Thursday night. To be a day 6 forecast there is surprising agreement among the GFS/ECMWF/Canadian models with the timing of this front. Cooler northeasterly winds behind the front should suppress temperatures by 5-10 degrees on Friday. As the ridge rebuilds again Friday night the front should return north with our temperatures rising well above normal again on Saturday. I`ve kept the forecast dry through the period as it appears each day`s cumulus field should be capped off by a subsidence inversion 6000-9000 feet AGL associated with the strong upper ridge. While it`s possible a sprinkle or light shower could develop from shallow diurnal convection beneath this inversion, coverage of rain should be less than 10 percent each day. The best potential for a shower might be on Wednesday as both the GFS and ECMWF show a pocket of enhanced mid-level moisture passing across the central and western Carolinas during the day. && .AVIATION /06Z SUNDAY THROUGH THURSDAY/...
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As of 06Z...LIFR to IFR visibilities and ceilings in fog and stratus this morning will dissipate as drier high pressure builds down behind a cold front today. The SW to W winds will continue to veer around to the N as the front drop through the area early this morning. Moisture profiles and soundings show column drying out leaving VFR conditions mainly after 15z. Expect northerly winds behind the front to veer around to the E tonight as the high pressure moves off the Mid Atlantic coast and the front begins to return north as a warm front. The on shore flow of marine moisture and weak isentropic lift associated with warm front will bring VFR to MVFR ceilings, mainly between 3k and 5k ft, back into the terminals tonight, by 06z. Extended Outlook...Tempo MVFR/IFR/SHRA cig/vsby Mon. Becoming VFR Tue. VFR/SHRA Wed. VFR Thur.
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&& .MARINE...
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NEAR TERM /THROUGH SUNDAY/... As of 1000 PM Saturday...Progressive wx features to continue. Mesoscale warm front at the same time will push inland while lifting to the north. Winds will veer to the SE-S 10-15 kt by midnight and further veer to the SW at 15 to 20 kt by daybreak as the sfc pg tightens ahead of the fast approaching cold front. Ocean Sfc Dewpoints are not progged to reach widespread 60s which is needed with latest SSTS having recently risen to the mid and upper 50s. As a result, have cut down on the sea fog however area inlets and the intra-coastal waterway will see some reductions in vsby from land based fog. Significant seas will run 2 to 3 ft with 4 footers possible by morning. Short period and choppy wind driven waves will dominate the sig. seas. Previous.................................................... As of 300 PM Saturday...Northeast surge has weakened considerably during the last 2 hours or so and the SCA was allowed to expire at 2 PM. Surface high continues to build down the coast but as its influence weakens a front, stalled south of the area, will lift north later this afternoon and evening as weak low pressure in eastern GA moves northeast. The front is expected to lift north and west of the waters tonight with a brief period of enhanced southerly flow around midnight. Speeds may briefly touch 20 kt but not for a long enough duration to warrant any headlines. The exiting low will be followed by a cold front, pushed well south of the waters a little after daybreak Sun. Cold advection behind the front does not appear particularly strong however, the gradient will result in wind speeds on the high end of the 15 to 20 kt range. Seas falling to 2 to 3 ft overnight will start to build as northeast flow develops and then increases Sun. Most areas will experience 2 to 4 ft seas but isolated portions of NC zones could see 5 ft late in the period. SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/... As of 300 PM Saturday...Wind turns onshore Sunday night as a warm front approaches the coast. Then on Monday a turn to SE expected as the boundary moves northward. High pressure center shifting from our north to west Atlantic Monday night will turn winds southerly. Wind speed and seas will show a gradual downward trend for the entire period. LONG TERM /TUESDAY THROUGH THURSDAY/... As of 300 PM Saturday...Strong high pressure will build off the East Coast next week, bringing gentle southerly winds Tuesday and Wednesday. By Thursday winds should veer more southwesterly in advance of a backdoor cold front that is expected to reach the Cape Fear area sometime Thursday night. This should be a very warm airmass, perhaps too warm for any sea fog to develop despite an otherwise favorable situation. A large region of easterly and southeasterly winds south of the big Atlantic high should produce a 9-second southeasterly swell that could reach 3 feet out at 20 miles distance from shore. Shorter period wind waves of 1-2 feet are also expected.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ NEAR TERM...DCH/III SHORT TERM...TRA LONG TERM...MBB AVIATION...RGZ

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