Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 180831 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 431 AM EDT Sun Mar 18 2018 .SYNOPSIS... A southward moving cold front, with isolated showers ahead of it, will move across and south of the forecast area by midday. Lingering clouds and weak high pressure with slightly cooler temperatures, will be on tap this afternoon through early Monday. A warm frontal passage will occur late Monday, prior to it, there will be a chance for light rain. This will transition to convective type precipitation as the atmosphere becomes increasingly unstable late Monday night thru Tuesday night. Much colder air will infiltrate the forecast area Wednesday thru Friday, and if enough moisture is available, wintry precipitation may mix with ongoing light rain Wednesday night, with all precipitation ending early Thursday. High pressure accompanied by a much drier and colder air mass, will settle in Thursday thru Friday. The next chance for rainfall will come from a low pressure system that will push across the area next weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 3 AM Sunday...a short-wave trough seen in the GOES-East water vapor imagery is in Virginia and northwestern North Carolina. This short-wave trough will shift to the Atlantic coastline north of the forecast area. The impact of this wave has been the convection that developed to our north along the frontal boundary and will move into the northern part of the forecast area before sunrise. This wave will force the frontal boundary back south today. The models are depicting the front to shift into to Georgia on Sunday. A developing surface low pressure area over the southern plains will cause the surface front well to our south to begin shifting northward with isentropic lift of the 295K surface seen to begin late Sunday. The condensation pressure deficit does not indicate saturation of the layer until after 12 UTC Monday. So for precipiation expectations, a dry Sunday is expected with low stratus on the north side of the front dissipating by mid-morning. The increase of cloud cover will begin late Sunday with a slight chance of showers after midnight mainly over northeast South Carolina. Maximum temperatures will be cooler on Sunday with the frontal passage. Temperatures will range from the lower 60s in the northern portions of southeast North Carolina to the lower 70s in Williamsburg and Georgetown counties. Lows Sunday night will range from the lower 40s in the north to around 50 in the southern sections of northeast South Carolina. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... As of 344 PM Saturday...ECMWF/GFS both show an upper low across the Central Plains Sunday night. The upper low is progged to translate across the MS Valley during Monday evening. At the surface, a cold front will be aligned south of the forecast area at the onset. In the meantime, an area of isentropic lift and increasing low-level theta-E advection will bring rainfall chances back into the area Sunday night. Mentioned a slight chance of thunderstorms as well with some elevated instability present late Sunday night into Monday morning, primarily for SC zones. By early Monday evening both GFS/ECMWF position a surface low across TN with the warm front returning north across the area with decent rainfall chances continuing. Included thunderstorms during this time frame as stability decreases across the area. The ECMWF tracks the low a little further south, but given either solution our rainfall chances will be on the high end across the forecast area. Blend of MAV/MET numbers appears reasonable through the period. Would not be surprised to see the convective risk areas shifted a little farther north for Monday, but the bulk of the instability will likely stay farther south. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... As of 344 PM Saturday...Low pressure pulling off the coast will bring a lull Tuesday, before another low develops and brings periods of showers Tuesday night through Wednesday, changing over to snow or a rain/snow mix Wednesday evening. Forecast low temperatures and thermal profiles, depict a brief period of frozen precipitation is possible across much of the area. Sharp mid- level drying will end PCPN prior to daybreak Thursday. Significant accumulations are not expected due to warmer ground, but a "Frost` advisory, or `Freeze Warning` may be needed very early Thursday, favored over interior SE NC, but could reach into parts of NE SC. Did not include thunder this period because of stable/cooler low levels, but elevated instability will exist to some degree. QPF Tue- Wed night averages to 3/10" to 5/10". && .AVIATION /08Z SUNDAY THROUGH THURSDAY/... As of 06 UTC...A frontal boundary stretches from south of KHSE to south of KRDU and to a low pressure center near KHKY. As an upper level shortwave moves across this boundary overnight the frontal boundary will shift again to south of KMYR and KFLO taf sites. Elevated convection is possible but expected farther north of KLBT and KILM and the South Carolina TAF sites are expected to remain precipiation free overnight. As the frontal boundary shifts south a few hours of IFR ceilings is expected mainly after 09 UTC and clearing by 13 UTC as there will be drying aloft boundary layer mixing during the morning. Extended outlook...Periods of MVFR Sunday through Wednesday. Chances for convection increasing Monday through Thursday. && .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 3 AM Sunday...currently southwest winds of 15 to 20 knots are occurring at Frying Pan Shoals buoy with seas of 4.5 feet. Closer to the coast seas are running 2.5 feet 10 miles southeast of Wrightsville beach where winds are southwest at 10 knots. The frontal boundary which has been waffling north to south and south to north the last few days will again shift southward through the entire forecast area by today. The wind direction will change quicly from the southwest to the northwest later today. Overnight the winds will continue veering to the east and southeast by late Sunday night. SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/... As of 344 PM Saturday...Weak high pressure across eastern NC at the beginning of the period will shift eastward Monday morning. A stalled front south of the waters will begin to lift north as another area of low pressure takes shape across the MS Valley. The initial easterly wind will veer to a southeasterly direction Monday morning. Additional veering is expected as low pressure moves across NC Monday night. Thus a stronger southwest fetch will develop with Small Craft Advisory conditions possible overnight Monday. Seas will be highest in the southwest fetch late Monday night. LONG TERM /TUESDAY THROUGH THURSDAY/... As of 344 PM Saturday...This is shaping up to be a difficult marine period, as a series of strong low pressure systems impact the coast. Gusty SW winds 20-25 KT Tuesday and Tuesday night, will shift to north equally strong, if not stronger Wednesday as N and NW winds kick up in a cold air surge. Gusts to near Gale force are not out of the question Wednesday over the outer waters, with current numerical wave guidance at FPSN7 assigning 7 feet Wednesday. Very cold temperatures will greet mariners early Thursday, in a moderate, but biting, offshore wind. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...JDW NEAR TERM...DRH SHORT TERM...DCH LONG TERM...MJC AVIATION...DRH is the U.S. government's official web portal to all federal, state and local government web resources and services.