Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 210019 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 819 PM EDT Thu Jul 20 2017 .SYNOPSIS... Showers and thunderstorms will be isolated in the days ahead, as an upper ridge builds from the west. The ridge will bring hot and humid conditions through the weekend. Rain chances will increase early next week as a surface trough deepens inland. && .NEAR TERM /THROUGH FRIDAY/... As of 3 PM Thursday...NVA and height rises associated by the retreating upper low working together with ambient subsidence associated with offshore convection to keep the much of the coastal plain not only rain-free but also hampering cu development. The area is shaping up for a muggy night with a continuation of light winds. Any patches of fog will only be of aviation concern as visibilities below 5SM do not appear in the cards. Tomorrow differs from today in that the aforementioned sources of downward vertical motion will be no more. With higher temps aloft and weak surface warm advection afternoon temps will soar into the mid 90s coast and upper 90s inland. There was some talk of a Heat Advisory but boundary layer hydrolapse rates seem to call for dewpoints that will fall during peak heating and preclude the 105F apparent temperatures needed across most of the area. This idea may be revisited by the evening and overnight crew however as the WRF in particular is less enamored with the idea. && .SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/... As of 3 PM Thursday...Deep layer high pressure will dominate the conditions through the short term period. Mid level moisture will be lacking and most of the guidance is keeping the area dry through the period. Temperatures will be several degrees above normal most notably with Saturdays highs with upper 90s in the most northwest/inland zones. We will once again be on the cusp of a heat advisory depending on the dry air mixing down in the afternoon which may modify the apparent temperature just enough to preclude the 105 clip needed for three hours. Overnight lows remain steamy in the middle to upper 70s. && .LONG TERM /SUNDAY THROUGH THURSDAY/... As of 3 PM Thursday...Long term will be marked by gradually decreasing temperatures and increasing chances for precipitation as ridging at the surface and aloft breaks down and a cold front approaches and then moves across the eastern Carolinas. A consensus of guidance has the front stalling in our vicinity by late Tuesday or Wednesday, where it will linger into Thursday. Above normal temperatures Sunday and Monday will drop back down to or below climo for the remainder of the long term. Tuesday looks to be the best day for convection, with deep moisture in place in advance of the impending front. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/...
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As of 00Z Friday...Looking at mainly VFR conditions this fcst package. The only exception will be from 07z-12z at which time vsby may reduce to 3sm to 5sm in BR due to calm winds. South to SW winds at 5 to 10 kt will diminish to SW-WSW at 4 kt or less after midnight. Models do not show any LLJ for FRi early morning and therefore have indicated tempo calm winds with MVFR vsby from BR. Progs indicate the mid-levels ie. 500mb will warm to -3 to -4 degrees C on Fri. This relatively mild air aloft will keep a lid on thunderstorm development with diurnally driven cu possibly reaching moderate cu stage before flattening out. Could see 4k to 5k sct to possibly bkn cu. Did not even include vcts or any prob30 groups for thunder. The sea breeze circulation will start early with the myrtles seeing southerly 10 kt winds by midday becoming gusty in the 10-15kt g20kt. The ILM terminal will see the sea breeze push thru around 19z with winds slightly lower both sustained and gusts when compared to the Myrtles. The inland terminals will see WSW 4 to 8 kt from 13Z thru 22Z backing to the S-SSW at 5 to 10 kt due to the aggressive sea breeze boundary pushing well inland. Extended Outlook...Mainly VFR with possible morning MVFR from BR. Brief MVFR/IFR possible in scattered showers and tstorms Mon and Tue due to a slowly approaching cold front from the NW.
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&& .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 3 PM Thursday...Winds have been light and somewhat variable today but a southwesterly direction will gradually come to dominate through the period. The reason being the pressure gradient-disturbing upper low will retrograde adequately for the Atlantic high to re-assert itself. Spectral plots show twin peaks of wave power at both 8 and 13-14 seconds, the latter being a ESE swell that will persist. As the wind picks up by up to a category the dominant period will shorten some but overall wave heights will not change significantly. SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... As of 3 PM Thursday...Bermuda High Pressure will keep southwest winds flowing across the coastal waters through the period. Some daytime increase in winds are expected with a decent sea breeze Saturday as it will be one of the warmest days of the year. Also the inland through will be enhanced by the heat which in turn will strengthen the low level jet overnight Saturday. Expect speeds to increase from the standard 10-15 knot range to 15-20 for a few hours. Significant seas will be 2-4 feet but a few five footers may develop overnight depending on just how much winds increase. LONG TERM /SUNDAY THROUGH TUESDAY/... As of 3 PM Thursday...Circulation around high pressure over the western Atlantic will keep winds from the SW through the period. An approaching cold front may briefly tighten the gradient enough to warrant Exercise Caution headlines or a Small Craft Advisory late on Monday, but confidence on this is low at this time. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...REK NEAR TERM...MBB SHORT TERM...SHK LONG TERM...REK AVIATION...DCH

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