The auxiliary spillway on the Oroville Dam is likely to fail within the hour according to news reports.
Here is a link to The Sacramento Bee's emergency coverage.
UPDATE 6:53PM PST:
California Department of Water Resources has released this photo of the damaged spillway.
UPDATE 6:59PM PST: If you need an inundation map, it is here.
Here is the NWS's flash flood and flood warnings: