* WHAT...Flash flooding caused by excessive rainfall is possible. * WHERE...Portions of southwest Iowa, including the following counties, Fremont, Mills, Montgomery, Page and Pottawattamie and Nebraska, including the following counties, Butler, Cass, Douglas, Gage, Jefferson, Johnson, Lancaster, Nemaha, Otoe, Pawnee, Richardson, Saline, Sarpy, Saunders and Seward. * WHEN...Until 5 AM CDT Sunday. * IMPACTS...Excessive runoff may result in flooding of rivers, creeks, streams, and other low-lying and flood-prone locations. * ADDITIONAL DETAILS... - Ongoing storm activity will combine with incoming storms from the west, with increasing flood chances through the overnight hours. Short-term models indicate that 3-5 inches will be possible, with rain rates of 1-2 inches or more in one hour already observed. - http://www.weather.gov/safety/flood