Increasing rain in Bay Area expected by Friday as second storm system bears down on region

The second system is expected to drop rain through Saturday.

A slow-moving storm system got the ball rolling on what is expected to be a handful of damp, cold days in the Bay Area, dropping a small amount of rain on Wednesday and into early Thursday ahead of another heavier system expected to arrive Friday.

The initial system produced about 1 1/3 inches of rain in Ben Lomond in the Santa Cruz Mountains over a 24-hour period ending at 6 a.m., as well as about two-thirds of an inch at Point Reyes of the Marin Coast, according to the National Weather Service. Those were the two highest totals in the region.

Closer to the East Bay, the rainfall was much lighter, with about a quarter-inch falling in Oakland, about two-tenths of an inch in Oakland and one-tenth of an inch in Concord and Livermore.

Those totals all are expected to increase with the expected arrival of the second system early Friday, National Weather Service meteorologist Rachel Kennedy said Thursday morning.

That system “is probably going to arrive sometime in the very early morning (Friday), about the time of the morning commute,” she said. “It should stay fairly light for the initial portion, but then there will be more moderate rainfall later in the mid-morning.”

The system arriving Friday also will turn up the wind gusts enough that the weather service issued a wind advisory along the coast from San Mateo through Big Sur, the East Bay Hills and the higher elevations of Santa Cruz, Monterey and San Benito counties. Wind gusts are expected to blow between 20-30 mph steadily through the region and as high as 45 mph along the coast and in the hills.

It also will keep the rain falling through Saturday, according to Kennedy. That rain is expected to give way to isolated showers only by Sunday. In all, at least a half-inch of rain is expected to fall before that system finally departs.

The first storm system was expected to linger through Thursday morning before clearing in most of the region, Kennedy said. Rain is expected to last through the afternoon and possibly into the evening in Sonoma County.

By Monday, most of the rain in the region should be finished, and a decent dry spell is likely, Kennedy said. A high-pressure ridge is expected to build early next week, and sunny temperatures with temperatures in the 70s and scattered clouds expected.