National Weather Service
Area Forecast Discussion

930 PM EDT Fri May 29 2020
SYNOPSIS
Showers and thunderstorms will move out of the area this evening as a cold front moves east of the Ohio Valley. A drier and cooler airmass will settle into the region for the weekend.



NEAR TERM
UNTIL 6 AM SATURDAY MORNING
A cold front has cleared through the ILN forecast area this afternoon and evening, and precipitation associated with the front is just about out of the area -- with just a few showers remaining in northeast Kentucky and far southern Ohio. A secondary cold front is now about to enter the area from the west, but this front has done little more than lead to an increase in clouds and a few light showers over northeast Indiana. Some low-end PoPs were kept in the forecast for a few hours in the northeast part of the ILN CWA, but this front should come through dry at almost all locations.

Immediately behind the initial cold front, winds shifted to the northwest. The area just ahead of the second front, however, has been characterized by light and variable wind flow -- calm in some places. This regime of light flow is now moving into the western sections of the ILN CWA. Later in the overnight hours, under clear skies, these light winds will set up over the eastern part of the forecast area. Some patchy fog may develop, and this has been added to the forecast for the southeastern ILN CWA -- particularly in the Scioto River valley.

Previous discussion > An upper-lever trough and surface cold front are swinging through the Ohio Valley. Widespread showers and storms have formed southeast of the cold front in the warm and humid airmass. Thunderstorms have been widespread thanks to the lower and upper level forcing running into the uncapped, low to moderately unstable (MLCAPE around 1000 J/kg) air east of the front.

Most thunderstorms have remained well below severe criteria in part due to shear being fairly weak. However, there still remains as non- zero threat for isolated strong wind gusts and hail east of I-75 where the greatest shear and instability exist this afternoon. Additionally, some locations have received multiple rounds of heavy rain in excess of 2 inches leading to the potential for isolated flash flooding.

The cold front will move east of the Ohio Valley later this evening and northwesterly winds will advect in cooler, drier air behind the front as high pressure approaches from the northwest. Forecast lows drop back into the middle 50s. Some pockets of reduced visibility are possible tonight due to dropping temperatures and the abundance of low-level moisture.



SHORT TERM
6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT
High pressure will build in from the northwest on Saturday. Northwesterly winds from 10-15 mph will usher and cooler and drier air. Forecast highs are near 70 in central Ohio and lower 70s near the Ohio River. Sprawling cumulus is expected to develop during the daytime due to the abundance of low-level moisture.

Tranquil weather continues Saturday night as light northerly winds continue to usher in cool air from the north. Forecast lows are in the upper 40s in central Ohio and near 50 by the Ohio River under fair weather skies.



LONG TERM
SUNDAY THROUGH FRIDAY
Extended period begins with Canadian high pressure over the western Great Lakes/Upper MS Valley. The high works eastward during the day on Sunday, reaching Ohio Sunday night. Still seeing some cold air advection at 850mb, so expect some cumulus development, but not as much as occurred on Saturday. Highs on Sunday will range from the mid 60s in the north to around 70 in the south. With the high centered over the region Sunday night, skies should be clear, allowing temperatures to drop into the mid to upper 40s.

The high pressure will slip off into the Appalachians on Monday. This will put the region on the backside of the high, allowing temperatures to start to rebound. Highs will push back into the lower 70s Monday afternoon.

Pattern begins to change as a large H5 ridge builds over the middle of the country Monday night into Tuesday. This puts the Great Lakes in northwest flow. Models continue to show the development of several rounds of convection developing over the upper Great Lakes. They then drop southeast across the Upper Ohio Valley. The ECMWF remains the quickest and furthest south with the pcpn, while the GFS and CMC are farther north. Will run a blend to come up with lower chance PoPs in the northern counties Monday night into Tuesday.

A shortwave in the northern stream flattens the upper ridge on Wednesday. This allows the pcpn to work farther south into the region. Models linger convection over the region into Thursday, before high pressure building in from the north displaces it to the south.



AVIATION
02Z SATURDAY THROUGH WEDNESDAY
Precipitation chances have ended at the TAF sites. Winds have shifted to the NW, and will remain in the 10-15 knot range for an hour or two, before diminishing to around 5 knots overnight. While some brief MVFR ceilings are still around the area as of 22Z-223Z, VFR skies are expected after 00Z.

Visibility restrictions are not completely out of the question overnight, though this looks slightly more favorable for KILN/KCMH/KLCK. For now, a 5SM BR has been added at KLCK.

No significant weather is expected tomorrow, with fair weather cumulus (VFR) and NW winds of around 10 knots.



OUTLOOK

Thunderstorms are possible on Wednesday.



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