As reported here Sunday morning, an overnight power outage lasted only two hours for 6,000+ affected in North Highline and Burien, but 10 hours for a West Seattle pocket at the east end of the Roxbury corridor. Seattle City Light spokesperson Julie Moore tells WSB what happened:

The cause was a failed cable. We were able to rule out issues along most of the route and restore power to the majority of customers pretty quickly. However, the last 40 took longer because we needed to patrol the overhead feeder that runs through a right of way to rule out other potential issues. Due to the terrain and other environmental conditions in that right of way, we needed to wait for daylight to do that patrol.

Part of the same area was affected by an outage the previous weekend; that one was blamed on a fallen tree.