Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 211858 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 258 PM EDT Thu Sep 21 2017 .SYNOPSIS...
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A mid level ridge of high pressure will set up over the Great Lakes and remain stagnant into early next week. Weather conditions are expected to be generally dry, with temperatures above normal through the weekend.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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An elongated mid-level ridge remains in place from the eastern Great Lakes into the middle/lower Mississippi Valley region, with the ILN CWA on its eastern periphery. At the surface, high pressure extends from well to the northeast into the Ohio Valley, overall providing for a stagnant weather pattern. There is plentiful low-level moisture (dewpoints in the upper 60s to lower 70s are exceeding most model forecasts by a couple degrees) and with temperatures reaching the middle to upper 80s, the warm layer near 800mb has been breached in an isolated fashion -- even despite little to no forcing. Though impossible to pick out on surface obs, there seems to be some weak convergence running across the ILN CWA from SSW-to-NNE. A persistence forecast appears best suited tonight, with another round of fog development likely -- with some chance of getting dense fog in a few spots, particularly in river valleys. Based on how dewpoints have progressed today, it also appeared reasonable to follow some of the raw model trends and increase min temps tonight by a degree or two -- putting things in the middle to upper 60s by morning.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/...
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The stagnant pattern will continue into Friday, as the mid-level ridge strengthens slightly, and the surface high establishes itself a little more firmly into the northern Ohio Valley. Another day of near-full sun should allow for a slight warming in temperatures from today (Thursday), raising the possibility of seeing some 90 degree readings, mainly in the southwestern ILN CWA. It is another day where it is tough to get a clean read on precipitation chances, as forecast soundings again show that a weak cap will be present near 800mb. Despite this, model output again suggests that conditions may not remain completely dry. With a pattern almost identical to today, some low-end chance of showers may eventually need to be introduced, but this may not be possible until real-time trends are monitored -- and it would not be good to include this CWA-wide since almost all locations will remain dry. With a slight drop in dewpoints going into Friday night, temperatures will be capable of falling a little more than on Thursday night -- and min temps should be in the lower to mid 60s.
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&& .LONG TERM /SATURDAY THROUGH WEDNESDAY/...
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Large H5 ridge over the eastern U.S. will be the dominant feature through the weekend and into early next week. It will work with a surface high centered over the eastern Great Lakes to bring dry and much above normal temperatures to the region. High temperatures will be about 10-15 degrees above normal as they push into the mid and upper 80s. Morning lows be in the lower 60s. Extended models continue to differ in their strength and timing of front for the middle of next week. The ECMWF is the quickest with the front, brining pcpn Wednesday Evening into Wednesday night. The GFS is doesn`t bring the front and pcpn in until Thursday. The Canadian brings Maria into NC/VA and therefore doesn`t really have the frontal feature. Ran with a blend of the ECMWF/GFS for the last 48 hours of the forecast.
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&& .AVIATION /19Z THURSDAY THROUGH TUESDAY/... No significant changes to the TAFs or weather conditions today. Some very isolated showers will remain possible this afternoon, but chances appear too low to include in the forecast. This may occur again tomorrow. Otherwise, cumulus development (3kft-4kft) will occur, likely remaining VFR. Winds will be light and variable through the period. Fog will again be a concern tonight into Friday morning. MVFR fog is likely for all TAF sites, with a chance for IFR at KILN and possibly at KCMH/KLCK. KLUK will again be favored for dense valley fog. OUTLOOK...No significant weather is expected at this time. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Hatzos NEAR TERM...Hatzos SHORT TERM...Hatzos LONG TERM...Sites AVIATION...Hatzos

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