A conditional threat for heavy rain and flash flooding exists this evening into Tuesday morning. A line of thunderstorms is expected to move through the area with potential for at least 1 to 2 inch per hour rainfall rates and training thunderstorms. Areas that received recent heavy rainfall such as far southeast Nebraska will be more susceptible to flooding.

* 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, Cass, Douglas, Gage, Johnson, Lancaster, Nemaha, Otoe, Pawnee, Richardson and Sarpy.

* WHEN...From 6 PM CDT this evening through Tuesday afternoon.

* 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. - For flood safety information, visit weather.gov/safety/flood.