Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 201107 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 707 AM EDT Sun Aug 20 2017 .SYNOPSIS... A stalled front just inland from the coast will weaken and transition to trof of low pressure by Monday. High pressure will expand across the area from the western Atlantic Monday thru Wednesday, continuing the heat and high humidity. A modest cold front will approach from the northwest late Wednesday night. Latest weather models progress this cold front across the area early Thursday, and off the Carolina coasts and well offshore by late Thursday. Canadian high pressure will ridge across the area Friday thru Saturday bringing with it a temporary reprieve from the summer heat and high humidity. && .NEAR TERM /THROUGH TONIGHT/... As of 330 AM Sunday...A dissipating frontal boundary was lingering just northwest of the forecast area generally along the 70-degree dewpoint line as of 06Z. There will be potential for at least patchy fog development southeast of this boundary towards morning, especially in those areas that received rainfall Saturday afternoon. This boundary is expected to push a little further south today, which should limit any chance for widely scattered showers or tstms this afternoon primarily to the southern and eastern CWA. As this boundary isn`t much of a front, the air behind it will remain quite warm, with highs reaching the mid 90s. Slightly lower dewpoints, however, will keep heat indices from reaching advisory criteria, though will see values reach the low 100s. Nocturnal development over the waters Sunday night may drift north and impact the coastal zones, so will maintain a low PoP to account for this possibility. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... As of 330 AM Sunday...Cloudiness and increased potential for convection will threaten the viewing of the solar eclipse Mon afternoon. The hier chance for convection and associated cloudiness will exist across the southern ILM CWA and also across the coastal counties of the ILM CWA. The western Atlantic ridging aloft will expand westward across the FA and to the Gulf Coast states. However, a weak inverted trof aloft extending from the upper low over the central Gulf of Mexico early Mon, will weaken as it pushes onshore and inland during Mon. The dynamics from this feature combined with sfc features ie. sea breeze and whats left of a stalled front, will result in clouds and chance for convection. have kept POPs in the low chance category, mainly as mentioned earlier across the southern ILM CWA and the immediate coast. Have leaned toward the drier GFS this period which would support a better viewing chance of the solar eclipse. For Monday night thru Tue night, the western Atlantic ridging across the FA into the northern Gulf of Mexico will help keep a partial lid on convection across the FA. However, not strong enough to prevent sea breeze and Piedmont trof induced convection Tue afternoon and evening. POPs will remain in the low chance category. Convection ahead of a cold front late Tue night, will be on the doorsteps of the ILM CWA come daybreak Wed. As for daily max/min temps this period, both will run slightly above normal for this time of the year. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... As of 300 PM Saturday...High pressure will reside just off shore extending down from off the coast of the Mid Atlantic region on Tues. At the same time a broad ridge aloft on Tues will be displaced by a trough digging down from the northwest through mid week. This trough will push a cold front into the Carolinas on Wed reaching the Eastern Carolinas late Wed into Thurs and slowly moving off the coast into Fri. The models show it pushing far south and east to bring drier weather on Friday into Fri night across the forecast area. Initially expect moisture convergence along the coast early Tues along periphery of high with some convection along or off shore becoming enhanced by sea breeze front Tues aftn. By Wed, cold front reaches into the Carolinas with gradient tightening ahead of it with moisture pooling over the Eastern Carolinas and dynamics aloft on the increase. Pcp water values will be above 2 inches with convection on the increase ahead of the front as it drops southeast into the area Wed night into Thurs. Drier air with lower temps expected by weeks end as front moves off the coast by Fri. Looks like we may even see a decent northeast surge behind front by late Fri. As it looks now, inland should begin to dry out Thurs night with moisture slow to leave the coast on Fri. Temps will start out warm into mid week ahead of the front, near 90, but will drop off to the mid 80s Thurs into Fri as front pushes south and east. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/...
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As of 12Z...IFR/LIFR conditions inland terminals thru 13-14z due to FG and VV. Coastal terminals will see MVFR from BR thru 13Z. All terminals from 14Z thru this aftn and evening will see VFR conditions. Will see diurnal Cu develop by late morning and persist into the evening in the 3.5K to 5.0K foot levels. Did not include any TSRA with convection coverage overall being isolated. If anywhere, the sea breeze or the dissipating stalled front just inland from the coast could provide the lift for isolated storms. Synoptic Winds generally start out from the ENE 5 kt and veer this aftn and evening to the SE-S 5 to 10 kt, except around 10 kt across the coastal terminals due to the aid of the sea breeze or in this case, the resultant wind boundary. Winds will quickly lower after sunset with most terminals becoming calm by midnight thru the predawn Mon hrs. Fog, possibly dense inland, will again make an appearance across all terminals after 06Z. Extended Outlook...Increasing coverage of showers/tstms by Tue through Wed. Flight restrictions will also be possible each early morning due to stratus/fog Wed.
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&& .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 330 AM Sunday...Bermuda high offshore will result in southwesterly flow around 10 kt across the waters this morning, but the approach of a dissipating frontal boundary may introduce some variability in the wind direction by midday. The gradient will be weak, and speeds are expected to remain around 10 kt through the period, supporting wave heights of around 2 ft. The exact location of the boundary will be difficult to forecast, and if it slips far enough south, some areas within the nearshore waters will experience a brief period of northeasterly winds. Isolated to scattered showers and thunderstorms will also be possible over the waters, mainly this evening and overnight. SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/... As of 330 AM Sunday...Sfc ridging will extend across the local waters from the Western Atlantic high during this period. At the start of this period, the ridge axis will extend inland north of the local waters. This will result in E to SE wind directions during Mon. The sfc ridge axis will drop southward across the local waters Mon night and Tue, and by Tue night, this ridge axis will be south of the local waters, extending inland vicinity of Georgia and northern Florida. This will result in veering wind directions, becoming south Mon night into Tue, and SW Tue night. The sfc pg will remain relaxed Mon thru early Tue with wind speeds 5 to 10 kts. The sfc pg will be in a tightening phase late Tue thru Tue night ahead of an approaching cold front. This will yield windspeeds in the 10 to 15 kt range. Significant seas will initially commence around 2 ft Mon thru early Tue and increase to 2 to 4 ft late Tue thru Tue night. An ESE, 1 to 2 foot ground swell at 7 to 8 second periods will initially dominate the seas spectrum. Wavewatch3 and Swan models indicate this dominating swell will increase to 2 to possibly 3 feet with periods also increasing to 9 to 10 seconds Tue thru Tue night. LONG TERM /TUESDAY THROUGH THURSDAY/... As of 300 PM Saturday...Southerly winds around high pressure extending down from off the Mid Atlantic coast will become more SE Tues aftn in sea breeze but will remain basically 10 kts or less. Winds will begin to veer and increase out of the southwest Tues night into Wed as a cold front makes its way into the Carolinas tightening the overall pressure gradient. This front will make it into the Eastern Carolinas Wed night into Thurs with stiff SW winds continuing ahead of it. The winds will begin to veer late Thurs into Fri as the front makes its way into and through the waters. Shower and thunderstorm activity will be on the rise ahead of the front through mid week. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...DCH NEAR TERM...CRM SHORT TERM...DCH LONG TERM...RGZ AVIATION...DCH

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