Scattered storms will develop today into this evening in an area including Mercer County, Ohio, the National Weather Service said.
Some of the storms will contain very heavy rainfall with localized flooding possible, the weather service said in its outlook.
A few of the stronger storms may produce strong wind gusts, the outlook said.
There is a low chance for thunderstorms this afternoon in a nine-county area of northeast Indiana and northwest Ohio, the weather service said. It said severe storms are not expected.
The nine counties are Allen, Adams, Huntington, Wabash, Wells and Whitley in Indiana and Defiance, Paulding and Van Wert in Ohio.
Heavy rainfall is possible in the 10 counties this weekend, especially late Saturday into Sunday, the weather service said. It said isolated flooding is possible, along with significant rises on larger rivers in the Wabash and Maumee river basins into early next week.