* WHAT...Flash flooding caused by excessive rainfall continues to be possible. * WHERE...Portions of southwest Iowa, including the following counties, Fremont, Mills, Montgomery, Page and Pottawattamie and Nebraska, including the following counties, Cass, Douglas, Gage, Johnson, Lancaster, Nemaha, Otoe, Pawnee, Richardson and Sarpy. * WHEN...Through Tuesday evening. * IMPACTS...Excessive runoff may result in flooding of rivers, creeks, streams, and other low-lying and flood-prone locations. * ADDITIONAL DETAILS... - Recent heavy rainfall combined with potential for repeated rounds of thunderstorms this evening and overnight will lead to a flash flooding threat through at least Tuesday morning. Additional rounds of rainfall will be possible through the remainder of the week. If confidence increases in potential for heavy rain Tuesday night into Wednesday, part or all of the watch may need to be extended. - http://www.weather.gov/safety/flood