A winter storm that was only expected to slightly dampen the L.A. Basin pelted the Bay Area on Thursday, causing minor flooding and traffic woes for commuters.

A flood watch was also issued for Monterey, Santa Benito, Santa Clara and Santa Cruz counties as the storm system moved across California, creating the potential for heavy rainfall to cause small creeks and streams to breach their banks. Excess runoff could also create "ponding" in urban areas, the National Weather Service said.

Officials were forced to close a Highway 280 offramp in San Jose after a clogged storm drain created 5 inches of standing water.

In Marin County, a crumbling hillside gave way overnight, sending rocks tumbling onto the lanes of southbound Highway 101 in Sausalito near Spencer Avenue, ABC Bay Area reported. Several cars hit those rocks, resulting in flat tires and bent rims.

The rain was expected to start tapering off by midday before an even stronger storm system hits the Bay Area this weekend, potentially bringing up to 4 inches in some areas starting late Friday, forecasters warned.

Not so in parched Los Angeles, where the same system is only expected to bring the "slightest chance" of precipitation over the weekend, said meteorologist Dave Bruno with the National Weather Service in Oxnard.

ALSO:

Rizzo gets 12 years in prison, must pay $8.8 million in Bell scandal

Jay Z, Mayor Eric Garcetti expected to announce music festival

Top Centinela official says FBI probing superintendent's high salary

ason.wells@latimes.com

Twitter: @jasonbretwells | Facebook | Google+