OAKLAND -- Dangerous high winds overnight caused downed trees and power lines across the Bay Area Friday morning, hitting areas including Oakland and San Francisco hard.

Some of the aftermath could be seen this morning on Ritchie Street, about one block west of MacArthur in East Oakland.

A large tree was also blocking two lanes of Skyline Boulevard near Redwood Road in the Oakland hills. About 8 a.m. the roadway near Highway 13 was littered with tree branches being cleaned up by public works crews.

Across the bay in San Francisco, gusting winds were being blamed for knocking two stories of scaffolding into a set of power lines on Thursday night. The scaffolding was set up against a building under renovation at 20th and Deharo streets. PG&E crews were called out to fix the damage to the lines.

Heavy winds Thursday night toppled a tree onto a car on Valle Vista in Danville, Calif., Oct. 4, 2013.
Heavy winds Thursday night toppled a tree onto a car on Valle Vista in Danville, Calif., Oct. 4, 2013. (Denis Cuff/Bay Area News Group)

Also in San Francisco, a large tree blew over blocking three of the four lanes of traffic on Masonic Avenue and Fell Street Friday morning.

Meanwhile, the California Highway Patrol has issued a High Wind Advisory for the Dumbarton Bridge and the Bay Bridge, said Officer Ron Simmons.

Winds will continue to blow at 25-35 mph, with gusts up to 50 mph today, said National Weather Service Meteorologist Steve Anderson. The fastest winds will be in the North Bay mountains and the East Bay Hills, he said. The winds are expected to relax about 3 p.m. today.

Dry conditions and the high winds have triggered a Red Flag warning for elevations about 1,000 feet in the northeast Bay Area until 6 a.m. tomorrow, Anderson also said.

Staff photographer Laura Oda contributed to this report. Contact Natalie Neysa Alund at 510-293-2469. Follow her at Twitter.com/nataliealund.