* WHAT. Flooding caused by excessive rainfall is possible. * WHERE. Portions of central and west central Illinois, including the following counties, in central Illinois, Marshall and Stark. In west central Illinois, Knox. * WHEN. From this afternoon through late tonight. * IMPACTS. Excessive runoff may result in flooding of rivers, creeks, streams, and other low-lying and flood-prone locations. Flooding may occur in poor drainage and urban areas. * ADDITIONAL DETAILS. - Multiple rounds of thunderstorms with heavy rain are expected to pass over already saturated grounds. - http://www.weather.gov/safety/flood