Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 211812 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 212 PM EDT Fri Apr 21 2017 .SYNOPSIS... Cooler conditions will continue into the weekend, with some chances for rain, as the front stalls south of the area. Warmer conditions are expected from Sunday into next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Some light rain will be possible across southern portions of the forecast today closer to a frontal boundary. CAA and cloud cover will keep temperatures cooler today generally in the 50s and 60s. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... Based on theta-e / MSLP analysis, the Friday morning cold front is expected to stall and pivot just south of the ILN CWA by late Friday and into Saturday morning. Precipitation chances through Friday night and Saturday will be tied to mid and upper level support moving eastward across this front, ultimately ending up with a surface low passing south of the region at some point on Saturday. Regarding all of the above features, model timing/placement agreement is disappointingly and remarkably poor. If there has been any trend with the 00Z runs, it has been for a slightly more southerly frontal position. This -- if nothing else -- will help to limit the potential for instability or more significant deep-layer moisture, limiting the threat for heavy rainfall. Models are not unanimous on this, however -- the 00Z ECMWF remains further north with the front and thus with its axis of greater QPF. The 00Z NAM is at the other end, keeping the majority of the CWA dry after an initial batch of rainfall on Friday night. WRF-ARW/WRF-NMM/NSSL Realtime WRF forecasts are similarly split on details but not as dissimilar on the overall picture, helping to paint a picture for PoPs based on a compromise scenario. Based on the majority of the model guidance, along with relatively unimpressive SPC SREF probabilities for >1" rainfall, the heavy rain mention will be removed from the forecast. Thunder was also removed from the grids, with even elevated instability expected to remain south of the area -- though, it should be noted, the elevated frontal boundary will be slightly further north than the surface front. PoPs were raised slightly with an initial wave of generally lighter precipitation late Friday evening into the overnight, with the greater chance for more persistent rainfall across the southern CWA at some point on Saturday. On the north side of the surface boundary, and in a regime of NE flow, Saturday will be a notably cool day -- with max temps at least 10 degrees below normal, only forecast to reach the lower to mid 50s. Obviously, the way the precipitation forecast plays out will have a role in these temperatures, making this a little lower confidence than normal. A rainier day on Saturday might keep temps closer to 50, but areas that escape the rain could get a little warmer. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... Upper level low will continue to dig south into the Tennessee Valley Saturday night into Sunday. As it does, it will gradually lose influence on the region. Clouds will decrease from the north but will remain some in the south with a lingering threat of showers. Temperatures should rebound into the lower and mid 60s on Sunday with the highest readings expected where more sunshine will occur. For Sunday night into Monday, upper level low will rotate southeast toward the southeast United States coastline. The threat for precipitation will end in the south with all locations expected to have sunshine on Monday. With airmass modification and solar radiation, temperatures will warm into the upper 60s to the lower 70s. Weak high pressure ridging at the surface and aloft will influence the regions weather Monday night into Tuesday. Dry weather and airmass modification will continue the warming trend with 70s expected on Tuesday. For the period Tuesday night into Wednesday night, upper level flow will allow a frontal system to push into the region from the northwest where it may briefly stall out by Wednesday night. This will bring at least a chance of showers to the northwest zones Tuesday night, and then a chance of showers and thunderstorms to all locations Wednesday into Wednesday night. By Thursday, models suggest that the upper level flow may begin to amplify. If this occurs, frontal boundary will lift north as a warm front into the Great Lakes on Thursday. This will eventually take the threat of precipitation with it. Temperatures will become above normal by this time with upper 70s to lower 80s expected. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
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Rain will overspread the area tonight into Saturday. Some locations already have MVFR cigs and additional MVFR cigs will work into the region overnight. Winds will increase overnight as well with wind gusts around 20 to 25 knots. Vsbys will be reduced at times with the rain. OUTLOOK...MVFR ceilings and visibilities possible Saturday with rain.
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&& .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Hatzos NEAR TERM...Novak SHORT TERM...Hatzos LONG TERM...Hickman AVIATION...Novak

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