Bay Area: Sunny skies expected to give way to incoming storm

Bay Area residents can expect light to moderate showers starting Friday afternoon and evening, with colder weather continuing into the weekend.

Lamont Bain, a National Weather Service meteorologist, said there was a 70% to 90% chance of rain falling across the East Bay, Santa Clara Valley and Monterey Bay by Friday evening. There may also be a rumble of thunder and an appearance of lightning, he said, as there is a 20% chance of thunderstorms over the region.

The storm is expected to approach the North Bay area, bringing early spring showers with it as it passes over; by the late afternoon, the rain is likely to spread to San Francisco and the East Bay. Showers should have moved into position over the Santa Clara Valley by early evening.

The highs for Friday are expected to be in the mid-60s in San Francisco and Monterey Bay and around 70 degrees in San Jose, with lows forecast around 50 degrees in San Francisco, 49 degrees in San Jose and 48 degrees in Monterey Bay.

Bain said the chance of rain would dwindle to 20% to 40% by dawn Saturday. Over the weekend, the entire Bay Area will be affected by a cold front; rain and isolated thunderstorms will prevent temperatures areas in the East Bay, South Bay and Monterey Bay from rising out of the 50s.

Some people in areas near San Francisco and down toward Monterey Bay may see a 5% to 10% chance of thunderstorms, but its coverage is expected to be very isolated, Bain said. Most people will likely see showers over the weekend, but not thunderstorms. By midmorning and afternoon Sunday, the precipitation is forecast to dry out.