Kudos to Seattle City Light for a raw, but thorough, update on cause of last night’s outage, presented here in its entirety in case it’s gone when you check the link:

Power to the Highland Park, Delridge, White Center, South Park neighborhoods have been restored. Cause was unstable hillside sluffing off & trees falling into 26kv @ Highland Park Wy SW between W. Marginal Wy SW & SW Webster St. A crew is onsite to repair but ETR is unknown due to still unstable hillside. 1 customer remains out until perm repair is done.