Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 291838 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 238 PM EDT SUN MAY 29 2016 .SYNOPSIS... A weak cold front will move through the region tonight, providing a chance of showers and thunderstorms. High pressure will move in on Monday, with drier conditions expected through the middle of the week. Another cold front will approach the region on Thursday, bringing the next chance for precipitation. && .NEAR TERM /THROUGH TONIGHT/... With only some light showers remaining in the eastern sections of the forecast area, attention will turn to the approaching cold front just to the west. The front appears roughly coincident with a wide band of enhanced cumulus on visible satellite imagery. Current surface observations indicate that the front currently extends from around Lansing MI to Bloomington IN. There is a very slight wind shift (210-220 degrees to 240-250 degrees) and a notable change in dewpoints (upper 60s to lower 60s), but temperatures are virtually identical on either side of the boundary. With these parameters in mind, and knowing that the front is not moving quickly, it is apparent that frontal forcing is not going to be especially strong. Nonetheless, the first convective cells have begun to develop, and this activity is expected to grow during the next few hours. High-resolution computer model forecasts have, across-the-board, been too fast in generating convection today. This suggests their instability forecasts may have been aggressive. A modified 12Z KILN sounding with current conditions produces MLCAPE of around 1500 J/kg, which is close to current LAPS analysis values (with higher values approaching 2000 J/Kg just ahead of the front in eastern Indiana). Surface-based parcels may be able to add another 500 J/kg on top of that, and perhaps more importantly, SPC mesoanalysis and the aforementioned modified sounding both support values of DCAPE of 600-1000 J/kg. This means that where convection does develop and become mature, it will likely be deep, and will have the potential for strong to possibly severe winds. However, weak forcing and shear (0-6km bulk shear of only around 20 knots) will make it very difficult for storms to become organized. Thus, any severe threat will likely be more pulse-type than based on updraft longevity, but a marginal risk of severe winds and hail still appears a possibility. Storm chances will be highest in the western half of the CWA between 18Z-21Z, and will then move to the east between 21Z-01Z, gradually diminishing after peak heating has been passed. Dry and mostly clear conditions are expected for the entire forecast area after 03Z, as the slightly drier air mass behind the front advects into the area. With less moisture in the boundary layer, min temps will get to around 60 degrees in the northwestern CWA, with lower 60s elsewhere. && .SHORT TERM /MONDAY THROUGH MONDAY NIGHT/...
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Behind the weak front, no huge change in air mass is expected, though dewpoints will be 5-8 degrees lower than they were over the weekend. At the surface, high pressure will be centered over the lower Ohio Valley, providing light northwesterly flow across the ILN CWA. Drier conditions will allow for mostly sunny skies, and thus despite the wind shift, temperatures will again be able to reach the lower 80s across the entire forecast area. As the surface high spreads northeast across the region and into southern Michigan, tranquil conditions are expected on Monday night, with lows in the lower 60s.
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&& .LONG TERM /TUESDAY THROUGH SATURDAY/...
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High pressure will continue over the region Tuesday into Tuesday night. Warm temperatures in the lower to mid 80s will persist with lows in the upper 50s to the lower 60s. A mid level trough is still advertised to move from the northern and central Plains to the Great Lakes Region Wednesday into Thursday. Most of the region will squeeze out one more dry day on Wednesday as high pressure moves off to the east. There could be enough moisture and diurnal instability late in the day on Wednesday for a low chance of showers/storms far west. As the mid level trough moves through the region on Thursday, an associated cold front at the surface will move through as well. There are some minor timing differences, but the region is still expected to see a gradual increase in showers and storms Wednesday night into Thursday. Warm highs in the mid to upper 80s on Wednesday will be tempered on Thursday by clouds and the threat for precipitation. For Thursday night into Friday, the cold front is forecast to exit southeast of the region, ushering in cooler and drier air with the threat for precipitation ending. Highs on Friday will range in the 75 to 80 degree range. For the upcoming weekend, the upper level pattern will transition to a broad long wave trough over the Great Lakes and Ohio Valley. High pressure on Saturday will give way to a weak disturbance Saturday night into Sunday. Have kept a low chance of showers and storms with this system at this time. Temperatures will generally range from 75 to 80 degrees for highs with upper 50s to lower 60s for lows.
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&& .AVIATION /19Z SUNDAY THROUGH FRIDAY/... Shower development is expected to coalesce into a line of thunderstorms ahead of the passage of a cold front this evening. H5 trough in the Upper Midwest will pivot northeastward into the Great Lakes early this afternoon. Showers that develop in the warm sector ahead of the cold frontal passage will deepen with the heating of the day, and as the front approaches later today there may be enough low level shear available for a line of storms to develop and propagate eastward in the late day and early evening. skies will be VFR until storms roll through. Gusty winds and mvfr vsbys are expected in thunderstorms but timing cannot be gleaned at this moment. Will have to wait until the expected line develops and extrapolate positioning and timing with any amendments this afternoon. Sky cover will rapidly improve this evening in favor of generally clear skies overnight. Some fair wx cu may sprout in the drier if not cooler air behind the front tomorrow. OUTLOOK...Showers and thunderstorms are possible Thursday. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Hatzos NEAR TERM...Hatzos SHORT TERM...Hatzos LONG TERM...Hickman AVIATION...Franks

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