Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 222118 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 418 PM EST Mon Jan 22 2018 .SYNOPSIS... A cold front will sweep through the Ohio Valley this evening bringing showers and a chance of thunder. Colder air will filter back into the region tonight and Tuesday. A chance of snow showers will be observed Tuesday as an upper low tracks through the Great Lakes. High pressure will then bring dry conditions through the end of the week. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... Deep mid level low centered near Kansas City to lift nne into the mid MS VLY this evening. Associated sfc low will become vertically stacked with cold front pushing east across ILN/s FA this evening. Band of pre-frontal showers associated with axis of forcing from low level jet will continue to push east across the area this afternoon into the evening. Have timed this band of showers with a period of categorical pops. Convection starting to develop along the front over Illinois. Models solutions continue to show marginal boundary layer instability early this evening over the sw FA, so have continued a slight chance of thunder for a few hours. Dry slot to work into the area late this evening with wrap around pcpn associated with mid/upper level low moving into the northwest late. CAA will develop in the wake of the front with lows ranging from the upper 30s northwest to the lower 40s southeast. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/... On Tuesday the closed mid/upper low will track east through the Great Lakes. Southwest to west winds of 15 to 25 mph with gusts to 35 mph will usher colder air into the region Tuesday. Expect nearly steady temperatures in this CAA pattern. Lift from the low and steepening low level lapse rates will lead to scattered showers Tuesday into Tuesday night. Most areas will see rain initially then changing to snow from nw to se through the day into the evening. Little snow accumulation is expect prior to ending Tuesday night. Temperatures to drop to lows in the mid to upper 20s. && .LONG TERM /WEDNESDAY THROUGH MONDAY/...
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Behind the low pressure system exiting the area on Tuesday, the coldest air aloft will be moving through the area on Wednesday. This sets up Wednesday as the coolest day of the week, especially as surface winds will remain westerly -- neutrally-advecting at best. While the overall pattern will be gradually switching away from troughing and toward ridging, the 500mb flow will remain wavy, and there are expected to be one or two waves moving through the Ohio Valley and southern Great Lakes in the Wednesday-to-Thursday time frame. At the very least, this may lead to some periods of increased cloud cover (another factor to keep temperatures down on Wednesday) along with the possibility of some light precipitation. Based on the 06Z/12Z model runs there does not seem to be enough consistency in the placement of the forcing to add any PoPs to the forecast yet (a jet-induced stripe of weak ascent previously depicted for Wednesday has almost disappeared from the current runs). Broad surface high pressure will move east into the area from Wednesday night into Thursday, though it will be centered south of the ILN CWA. By Thursday morning, ridging over the Mississippi Valley will become more prominent, and increasing significantly by Thursday night into Friday. This will bring dry conditions and gradually warming temperatures through Thursday and Friday, remaining warm going into Saturday. In fact, the continual southerly flow will likely keep temperatures from falling much (if at all) on Friday night. Behind the departing surface high, and with troughing developing over the plains, moist flow from the Gulf is expected to move into the Ohio Valley again over the weekend. This very basic statement is about the only thing still in good agreement for the weekend forecast -- 00Z and 12Z operational GFS/ECMWF runs have eschewed consistency in favor of drifting further apart in their timing and amplitude depictions of the weather features through this period. In particular, it is the depth and speed of the upstream trough that seems to be a source of inconsistency regarding upcoming precipitation timing. The 12Z operational GFS is very fast and progressive with the trough, while the 12Z operational ECMWF is slower and stronger, with greater amplitude. This manifests in a roughly 24-hour difference in the timing of the greatest chances for precipitation. The 12Z GFS timing is a little more consistent with its own past runs, while the 12Z ECMWF timing is much slower than its 00Z cycle. However, it is definitely worth noting that several GFS ensemble members do not support the operational run, instead supporting the slower ECMWF solution. This all works to provide low confidence in how exactly the scenario will play out, though rain appears certain to occur at some point. Until timing gets into better agreement, PoPs will be capped at 50 percent. Conditions ahead of the trough will likely remain warmer than normal, but should cool down as an associated cold front moves through at some point in the period. Eventually, temperatures will probably end up close to the climatological normal by Monday, with drier conditions favored behind the front.
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&& .AVIATION /21Z MONDAY THROUGH SATURDAY/... A band of pre-frontal showers will push east across the TAF sites this afternoon. Generally expect continued VFR conditions with brief MVFR conditions in rain showers. Cold front to sweep east across the TAF sites early this evening. Winds will shift southwesterly with the MVFR CIGs developing in the cold air behind the front. Also, a slight chance of an embedded thunderstorms is possible at KCVG/KLUK between 0z and 3z, but this has been left out attm given limited chance and coverage. CIGs are expected to improve to VFR in the dry slot late tonight. MVFR CIGs will re-develop Tuesday with the mid/upper low tracking through the Great Lakes. Scattered showers will be possible Tuesday but have not been added to the forecast due to limited coverage and impact. OUTLOOK...MVFR ceilings likely through Wednesday. MVFR vsbys are possible Tuesday.at 50 percent. Conditions ahead of the trough will likely remain warmer than normal, but should cool down as an associated cold front moves through at some point in the period. Eventually, temperatures will probably end up close to the climatological normal by Monday, with drier conditions favored behind the front. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...AR NEAR TERM...AR SHORT TERM...AR LONG TERM...Hatzos AVIATION...AR

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