Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 232002 CCA AFDILM Area Forecast Discussion...CORRECTED National Weather Service Wilmington NC 302 PM EST Thu Nov 23 2017 .SYNOPSIS... High pressure north of the area, and low pressure passing offshore overnight into Friday, will bring cool conditions along with occasional light rain and drizzle near the coast. A dry cold front will cross the coast Saturday night followed by cool and dry Canadian high pressure through early next week. A warming trend will follow through mid-week, as high pressure moves offshore, and low pressure approaches from the west. && .NEAR TERM /THROUGH FRIDAY/...
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As of 228 PM Thursday...Deep southwest flow maintains mid and high level moisture feed through tonight. The sharp 5h trough axis, which stays west of the area into Fri before weakening periodically ejects weak shortwaves which will move northeast, passing off the coast. Each wave develops a weak surface low, yet precip chances through the period will end up rather low. There will be some isentropic lift overnight with the surface highs to the north and then northwest building in. However, dry air with the highs keeps the lowest 4k ft or so dry. Another negative factor is the eastward drift of the 5h trough. This keeps the bulk of the best lift and moisture off the coast, stymieing precip chances. The only area with enough lift to generate light rain will be along the coast this evening as the initial surface/mid-level waves move up the coast. Even so, the very dry boundary layer coupled with the weak nature of the isentropic lift limits rainfall chances overnight. Prospects do not look much better Fri as far as rainfall is concerned. Seeing good agreement between the Canadian/EC/GFS/and NAM with all 4 of them showing the moisture and forcing shifting east and moving offshore by daybreak Fri. Skies clear from east to west Fri AM as surface high to the northwest builds in. At the coast clouds linger into mid- morning before skies clear out as mid and upper level flow becomes westerly. Temperatures through the period will run below climo. As skies start to clear out tonight and drier air spreads in from the northwest radiational cooling may develop in some of the typical western cold spots. Closer to the coast clouds and moisture will linger. Lows tonight will range from low 30s inland to around 40 at the coast. Skies will clear out for Fri but northeast flow will continue with only some airmass modification taking place. Highs will reach low 60s in inland areas with coastal locations running a few degrees cooler due to lingering morning clouds.
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&& .SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/... As of 228 PM Thursday...in the mid and upper levels the trough moves off the coast and several spokes of short-wave energy approaches from the west-northwest Saturday afternoon into the overnight. There is very little lift shown as most of the energy stay in Virginia and northward. Moisture is limited so only scattered clouds are expected through this period. Both of the 12 UTC global models, GFS and ECMWF, concur on no precipitation option. Lows on Friday night are expected to range from the middle 30s inland to the lower 40s at the beaches. On Saturday night lows are expected to be a few degrees warmer. The highs on Saturday are expected to be in the middle 60s. && .LONG TERM /SUNDAY THROUGH THURSDAY/... As of 228 PM Thursday...Intrusion of Canadian high pressure to dominate the first half of the extended period, with dry north breezes Sunday as the high barges in from the west, remaining exceptionally dry through Monday, although winds do ease Monday as the surface high centers over the area. Monday morning will be the chilliest portion of this period, with widespread 30s and sub-freezing air over parts of the interior. Tuesday through Thursday look for warming to trend, as return wind flow becomes established, and gradual amplification of a short-wave ridge over the area mid-week, as an upper low migrates eastward across the mid-Mississippi Valley. The moisture return will bring slight rain chances WED/THU days 6/7. No Arctic air or severe weather signatures noted on the horizon at this time. && .AVIATION /20Z THURSDAY THROUGH TUESDAY/... As of 18Z...High pressure to our west will give us fairly decent aviation weather today with a predominately mid cloud ceiling. A weak wave will ride up the eastern seaboard this evening. Still some uncertainty with respect to rain and ceilings, but think the coast has a decent enough probability to introduce some light rain, just before 00Z at the Myrtles. Ceilings will be lowest there also, but should remain VFR. VFR conditions are expected on Friday with northeast flow. Extended Outlook...Possible showers along the coast Saturday night, otherwise VFR. && .MARINE... NEAR TERM /THROUGH FRIDAY/... As of 228 PM Thursday...Northeast winds will continue through the period with pinched gradient this evening and overnight keeping speeds near 20 kt into Fri. Gradient has weakened a bit the last few hours with both winds and seas dropping a bit. However, low pressure moving northeast from northern FL will begin reversing that trend by this evening. Given the expectation of solid 20 kt winds overnight decided to extend the small craft advisory headline into tomorrow afternoon. The gradient starts to relax around midday Fri as elongated high centered to the northwest drifts east-southeast. Northeast winds will drop to around 15 kt tomorrow afternoon with seas falling from 3 to 6 ft this evening to 3 to 5 ft later Fri. SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... As of 228 PM Thursday...high pressure will give way to a cold front that will cross the waters near sunrise Saturday morning and shift east and south of the waters by Saturday night. This front will not be particularly strong. No precipitation is expected. The winds on Saturday night will be from the northeast at 15 knots then with frontal passage the winds will back to the west at 10 to 15 knots. As the high builds in the wind will veer back to the north at 15 to 20 knots late Saturday Night. Seas will range from 2 to 3 feet near shore Friday night to 4 to 5 feet at 20 miles off the coast. On Saturday the seas will drop only slightly to the 2 to 4 foot range. An increase to 3 to 5 feet between 10 to 20 miles off the coast is possible as a cold surge works it way south very late Saturday night. LONG TERM /SUNDAY THROUGH TUESDAY/... As of 228 PM Thursday...The extended marine forecast is one of improving conditions, as Sunday begins blustery in N wind as Canadian high pressure builds toward the coast. Following this however, a vast improvement, as winds ease and Monday into Tuesday, with light windspeeds. As a result, a notable easing trend in sea heights as well, with 3-4 foot seas Sunday, slowly subsiding to 1-2 feet into Tuesday. An `Exercise Caution` flag cannot be ruled out entirely Sunday, but afterward, manageable marine conditions appear on tap. No TSTMS expected on the 0-20 NM waters this period. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...Small Craft Advisory until 5 PM EST Friday for AMZ250-252-254- 256. && $$ SYNOPSIS... NEAR TERM...III SHORT TERM...DRH LONG TERM...MJC AVIATION...DL MARINE...

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