The heavy rain earlier this week in the Southern Willamette Valley could cause minor flooding of the Willamette River in Portland and the Columbia River.
The National Weather Service says river levels will crest just below flood stage, but flooding of low areas could happen.
The flooding could start as early as Thursday evening and will continue through Saturday when the river levels will recede.
The Columbia River could also have minor flooding as it backs up behind the flooded Willamette River.