BRAIDWOOD, Ill. (CBS) — A tornado warning has been issued for parts of Will and Grundy counties southwest of Chicago.

The tornado warning is in effect until 1:15 p.m. Friday for east central Grundy and southwest Will counties. At 12:49 p.m., the National Weather Service discovered a severe thunderstorm on its Doppler radar that could produce a tornado.

The storm was spotted near Braidwood and Wilmington, heading northeast around 20 mph. It was expected to pass through Wilmington and Lakewood Shores around 1 p.m., Channahon around 1:10 p.m., and Elwood around 1:15 p.m.

There is a severe thunderstorm warning in effect for parts of McHenry and DeKalb counties until 1:30.

There also is a strong line of storms moving upwards from the south toward the Chicago area.

The Weather Service advises anyone in the warning area to move to an interior room on the lowest floor of your house or building.