Watch Video :Heavy rain, strong winds slam San Francisco.Houses Destroyed by the storm..
A ferocious storm system brought heavy rain, powerful wind and power outages to Northern California Thursday, forcing San Francisco at one point to shut down its famed cable car system.
Truckers using the highly exposed Richmond-San Rafael Bridge -- which stretches across the northern end of San Francisco Bay -- were advised to avoid the structure because of high winds.
Pacific Gas and Electric reported 20,000 Bay Area customers without power.
KPIX-TV reports that electricity was knocked out in San Francisco from the Marina to the financial district and beyond.
The cable car system was shut down before the storm hit because of concern over the effectiveness of brakes on the aging cars in wet conditions.