The conditions are favorable for supercells to develop that are capable of producing hail up to 3 inches in diameter, wind gusts up to 75 mph and a few tornados, according to the weather service's Storm Prediction Center.
Affected counties include: Adair, Adams, Appanoose, Benton, Boone, Cedar, Clarke, Dallas, Davis, Decatur, Des Moines, Guthrie, Henry, Iowa, Jasper, Jefferson, Johnson, Keokuk, Lee, Linn, Louisa, Lucas, Madison, Mahaska, Marion, Marshall, Monroe, Muscatine, Polk, Poweshiek, Ringgold, Scott, Story, Tama, Taylor, Union, Van Buren, Wapello, Warren, Washington and Wayne
The National Weather Service has issued a tornado watch for 41 counties in Iowa stretching from east of the Des Moines metro area through the southeast corner of the state
The watch includes the Des Moines metro area, Ames, Iowa City, Cedar Rapids, the Quad Cities and Burlington until 12:00 a.m. Monday, Sept. 19.
NWS Des Moines @NWSDesMoines A tornado watch has been issued for parts of Illinois, Iowa and Missouri until 12 AM CDT