SAN FRANCISCO (Map, News) - San Francisco was rocked Friday by the powerful punch of the biggest winter storm in two years with high winds and heavy rains disrupting transit service, causing widespread power outages and road and bridge closures.

The winds were so powerful, blowing 40 mph to 50 mph with gusts reaching up to 70 mph, that a skylight was ripped off of Washington High School and scaffolding blew off a building at Third and Market streets, prompting the closure of a portion of this main thoroughfare and affecting Muni lines. Half of Muni’s routes were disrupted in some manner by the storm, such as the J-Church line, which stopped running after trees struck its overhead wires.

The storm died down early Friday afternoon. This weekend, The City is expected to see more rain, but nothing compared with Friday’s storm.

Roads were closed because of flooding, including the Great Highway and John Muir Drive. The storm lightened up by the afternoon, with winds and rain dying down, although not before dropping up to an inch of rain.

High winds brought down at least 400 trees or branches which contributed to loss of power for up to 62,000 Pacific Gas and Electric customers in the Noe Valley, Twin Peaks,

Bayview-Hunters Point, Sunset, Richmond and Mission neighborhoods. As of Friday afternoon, 57,000 customers were left without power and told to prepare for having no power throughout today.

Department of Public Works crews out in full force kept busy clearing clogged catch basins and removing fallen trees. The area along 11th and Mission streets was closed down after trees fell on top of Muni lines, but was later reopened mid-day.

DPW crews were expected to clear evening commuter routes and work through the night and today cleaning up the damage left in the storm’s wake.

Severe storm-related accidents occurred outside of The City with winds toppling over two big-rig trucks on the Richmond San Rafael Bridge on Friday morning, prompting the California Highway Patrol to close it down because of the high winds.

“This is the first time in many, many years that we’ve closed a bridge due to wind,” CHP spokesman Mike Davis said.

Golden Gate Bridge officials created a two-lane buffer between northern and southern traffic flows, but did not close the bridge. Ferry service in the Bay was also disrupted.

“Frankly, it’s just what you anticipated — downed trees, downed wires, arched wires, issues relating to flooding that exacerbated traffic conditions,” Mayor Gavin Newsom said. “But nothing of monumental consequence.”

The storm brought San Francisco International Airport to a near halt, causing up to four-hour delays and more than 80 cancellations of every airline, said SFO spokesman Mike McCarron.

Even access to SFO was hindered by the storm after winds felled trees, blocking BART tracks. BART ran buses from its 24th Street-Mission station for passengers headed to SFO, according to a BART spokesman.

Downed trees on the tracks caused two BART trains to be evacuated and service between the 24th Street-Mission and Daly City stations to be closed. Trains traveling to San Francisco International Airport from north of Daly City also were stopped, BART spokesman Jim Allison said.

jsabaini@examiner

Examiner Staff Writers Katie Worth, Sasha Vasilyuk and wire services contributed to this report.