Area Forecast Discussion
Issued by NWS Wilmington, NC

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118 FXUS62 KILM 210150 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 950 PM EDT Sun Oct 20 2019 .SYNOPSIS... A weak ridge of high pressure will build south across the Carolinas tonight and Monday with dry weather expected. A cold front will move through the area Tuesday bringing a chance of showers and thunderstorms. High pressure and dry weather are expected Wednesday and Thursday, but rain chances may increase next weekend as a cold front approaches from the west. && .UPDATE...
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Forecast updated to cancel Small Craft Advisory over SC coastal waters where seas have dropped to below 6 ft. The headline remains until 1 am over NC coastal waters.
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&& .NEAR TERM /THROUGH MONDAY NIGHT/... Cooler and drier high pressure will continue to build in behind Post-tropical Cyclone Nestor as it continues to track off to the northeast through tonight. A few light sprinkles right along the shallow frontal boundary will diminish as the front tracks off to the east leaving behind shallow cool and moist layer. The gusty W-NW downslope flow should help to break up the clouds a bit, but soundings and moisture profile show a steep frontal inversion keeping very shallow moist layer across the area tonight. This is always tough to break and tough to forecast how long it will last. Will show some breaks from SW to NE as drier air wraps around the back side of low through early this eve. But will also maintain fairly widespread stratus around the area for tonight and possibly lasting through much of the day on Monday as cooler and drier air settles in with shallow residual moisture socked in under inversion. CAA behind front will keep an overall cooling trend in temps with most temps right around 60 by this eve. The overnight lows will be tougher, with most models showing a decent break in clouds through the first part of the night allowing temps to drop and then stratus layer should help level them off with some shallow CAA continuing. Lingering shallow moisture into Monday will maintain some low stratus but should see increasing sunshine through the day. Temps will be in the low to mid 50s tonight and highs Monday in the low to mid 70s. Temps may not reach that high if clouds hold on. By Mon night, winds will veer around to the SE to S with warm and moister flow ahead of approaching cold front. Expect clouds to increase and thicken after midnight, with showers moving in by morning. Temps will be warmer with overnight lows remaining in the 60s. && .SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/... Models have come into pretty good agreement that low pressure over the Great Lakes will push a cold front eastward and across the Carolinas late Tuesday afternoon into Tuesday evening. The best vorticity associated with the 500 mb trough will pass to our north across the central Appalachians, but there should be enough instability and deep-layer moisture for showers to become likely. Modest lapse rates should keep CAPE at or below 1000 J/kg despite high temps expected to reach the lower 80s, but 0-6 km shear over 40 kt should still promote some multicell organization of scattered thunderstorms. SPC has the area outlooked in a 5 percent severe risk for wind on Tuesday. Dry air will build in behind the front Tuesday night with skies gradually clearing overnight. Lows 50 inland and mid 50s on the coast. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... Confidence is high that Wednesday and Thursday will have nice weather conditions. High pressure over the Deep South on Wednesday will move east across the Carolinas Wednesday night, then offshore on Thursday. Mainly clear skies are expected with highs around 70 on Wednesday and in the lower 70s Thursday. Lows in the 40s Wednesday night and 50s Thursday night. Forecast confidence has become much lower for late in the week as strong shortwave energy dives south across the Rockies on Thursday. The 12z GFS wants this energy to remain progressive and shows a full-latitude trough racing across the country and off the East Coast Saturday night. The 12z Canadian along with the 00z and 12z runs of the ECMWF cut the shortwave energy off across New Mexico and Texas on Friday, leading to a much slower evolution of downstream effects across the Carolinas. I`ve reduced our forecast PoPs Friday and Saturday versus forecasts we had our 24 hours ago, but realize there is no obviously correct answer just yet with how this pattern will evolve. All models show enough onshore low-level flow off the Atlantic Friday and Saturday that I can show gradually warming temperatures into the weekend with rising dewpoints, but I`m keeping PoPs just a little above climo averages until some certainty evolves in this weather pattern. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... Stratus behind a cold front will move eastward over the next few hours leading to clear skies and VFR conditions across the area. NW winds will weaken and become calm. This, along with saturated soils from yesterday`s rainfall will lead to the development of inland fog and coastal stratus tonight. IFR conditions are likely to develop for brief period tomorrow morning at many of the forecast sites. Few or scattered VFR cumulus to develop tomorrow afternoon with decent boundary layer moisture. Extended Outlook...Chance for early morning fog/stratus Tuesday morning. Cold front expected to move through Tuesday afternoon/evening with VFR conditions following. && .MARINE...
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Small Craft Advisory extended until 1 am over NC coastal waters only as seas gradually lower this evening, from 4 to 7 ft down to 3 to 6 after midnight. Weak high pressure will build in behind Post-tropical Cyclone Nestor, as it tracks off to the northeast away from waters. Gusty W-NW winds on the back end will veer around to the N-NW and lighten to 10 to 15 kts through tonight and will continue to veer around to the NE to E through late Mon and eventually southerly by late Mon night ahead of approaching cold front. Seas will remain 2 to 4 ft most of Mon through Mon night. Shower and thunderstorm chances will increase on Tuesday as a cold front approaches from the west. Latest models increase S to SW winds to around 15 knots on Tuesday with seas building to around 4 feet. The front will move offshore Tuesday evening. High pressure over the Gulf Coast will build eastward Wednesday, crossing overhead Wednesday night, then moving offshore Thursday. This should lead to a period of strong offshore winds near 20 knots Tuesday night, then lighter and veering winds Wednesday through Thursday. The 12z GFS model may be an outlier with how quickly it brings the next cold front eastward on Friday. The slower Canadian and ECMWF models maintain lighter onshore winds during the day Friday.
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&& .ILM WATCHES/WARNINGS/ADVISORIES...
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SC...None. NC...None. MARINE...Small Craft Advisory until 1 AM EDT Monday for AMZ250-252.
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&& $$ SYNOPSIS...TRA UPDATE...MAS NEAR TERM...RGZ SHORT TERM...TRA LONG TERM...TRA AVIATION...MAS/21 MARINE...TRA/MAS/RGZ

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