* WHAT...Flash flooding caused by excessive rainfall is possible. * WHERE...Portions of Illinois, including the following areas, Bond IL, Fayette IL, Greene IL, Jersey IL, Macoupin IL, Madison IL and Montgomery IL and east central Missouri, including the following areas, Franklin MO, Saint Charles MO, Saint Louis City MO and Saint Louis MO. * WHEN...From Sunday morning through late Sunday night. * IMPACTS...Excessive runoff may result in flooding of rivers, creeks, streams, and other low-lying and flood-prone locations. * ADDITIONAL DETAILS... - Thunderstorms producing heavy rainfall moving over the same locations could produce flash flooding. Rainfall amounts of 1-3 inches are expected with locally higher amounts possible.