Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 151948 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 348 PM EDT Fri Sep 15 2017 .SYNOPSIS...
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An elongated area of surface high pressure will remain entrenched along the spine of the Appalachians through the weekend, providing dry conditions and warmer temperatures. A cold front will approach the area by Sunday night into Monday, bringing rain chances back into the area.
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&& .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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Surface high pressure has settled in along the spine of Appalachians -- which has provided a markedly warmer and sunnier day today than the past several days. Some diurnally- driven Cu continue to percolate across most of the FA, but a gradual clearing trend will evolve towards sunset with the loss of daytime heating. With the partly cloudy to partly sunny skies, temperatures have jumped into the mid/upper 70s area wide -- with a few locations at 80 degrees towards the Tri-State area of southwestern Ohio, southeastern Indiana, and northwestern Kentucky. Temperatures will drop off fairly quickly this evening with the decreasing cloud cover, with lows in the upper 50s to lower 60s towards the end of the near term period. Main item of interest for the overnight period will be the potential for some fog development -- especially in area river valleys. Setup does appear to be somewhat less favorable than earlier this morning with slightly drier conditions near the surface. However, a few model soundings continue to show a fairly notable near-surface inversion forming early Saturday morning with a zero degree surface dewpoint depression. As such, there remains the potential that LL moisture will become trapped underneath this inversion, especially near sources of low-level moisture (i.e. river valleys). Will highlight the localized threat for dense fog in river valleys in the HWO, although most areas will only see light fog.
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&& .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
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The short term period will start off with some patches of light fog and potentially some denser river valley fog -- all of which will burn off by mid-morning. With light southerly flow becoming established on the western side of the aforementioned broad surface high, even warmer temperatures are expected Saturday afternoon. Went close to guidance for highs generally in the lower 80s. Light southerly winds will prevail Saturday with partly to mostly sunny skies. A few high-resolution solutions have hinted at the potential for spotty isolated showers to develop across portions of Indiana and extreme western Ohio during the afternoon hours along a very weak surface convergent boundary. However, do think that this is overdone with the overwhelming lack of any focused forcing and absence of any deep high RH within the column. As such, have maintained a completely dry fcst for now for all areas. More tranquil weather conditions are expected for Saturday night. Went close to guidance for lows -- a degree or two either side of 60 degrees across the entire FA.
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&& .LONG TERM /SUNDAY THROUGH FRIDAY/...
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Broad upper level ridging will be broached by weak short wave energy cutting across the Great Lakes and Ohio Valley. A front will stall just northwest of the region. This combination will allow for primarily diurnally-driven, unorganized convection. Better chance of this will be in western counties. Appears that ridge will strengthen somewhat later in the week which should minimize precipitation chances. Temperatures will be unseasonably warm through the period.
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&& .AVIATION /19Z FRIDAY THROUGH WEDNESDAY/... The FG/BR from earlier this morning has long burned off, leaving in its wake just a few patches of MVFR clouds which are quickly transitioning to VFR. A fairly healthy Cu field has developed in response to diurnal heating, with densest coverage focused from the lower Scioto Valley through KILN up towards KDAY. Nevertheless, even if CIGs expand, they are expected to be VFR. Cu field will dissipate rapidly with the loss of daytime heating towards 00z. Skies will go mainly clear early in the overnight period, with just a FEW/SCT cirrus in the region. Model soundings are once again showing some low level moisture being trapped underneath a near-surface inversion, especially for S/E parts of the area. While most widespread FG/BR should be S/E of the local terminals, do think that MVFR/IFR VSBYs may once again develop towards sunrise Saturday -- with greatest VSBY restrictions for KILN/KCMH/KLCK with river valley fog at KLUK. Setup appears a bit less favorable than what had developed earlier this morning -- owing to increasing dry air working into the area -- but residual VFR cloud cover should be more isolated than last night, helping enhance radiational cooling. Expect there may be some localized dense spots in area river valleys towards 12z. Any VSBY restrictions that develop will improve once again towards 13/14z Saturday, with some more diurnally-driven VFR Cu in the afternoon. Hi-res solutions are showing some isolated light SHRA developing towards the end of the TAF period for western terminals, but in increasing WAA scheme, this may be a tad overdone. As such, held off from inclusion in the fcst at this time. OUTLOOK...No significant weather is expected at this time. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...KC NEAR TERM...KC SHORT TERM...KC LONG TERM... AVIATION...KC

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