As California braces for another round of atmospheric rivers and storms, Gov. Gavin Newsom on Wednesday declared a state of emergency to support storm response and relief efforts in 21 counties, including five in the greater Bay Area.

Storms are forecast to pummel the state through mid-March, and many areas are already grappling with flooding, power outages and damage from recent record rainfall and snow storms.

The emergency proclamation issued Wednesday to provide disaster response and relief includes San Francisco, San Mateo, Santa Clara, Santa Cruz and Monterey counties.

Last week, a state of emergency was issued for 13 counties statewide that included Sonoma County, and the governor activated the California Guard and State Operations Center.

Bay Area communities are preparing for high winds and possible flooding as an atmospheric river approaches the region with heavy rains on Thursday and Friday.

A flood watch is in effect for the region from Thursday afternoon through Sunday morning, and a wind advisory is in effect for the entire Bay Area and Central Coast Thursday afternoon through Friday afternoon.

Lingering rain will continue into the weekend with yet another atmospheric river expected next week, according to the National Weather Service.

"The state is working around the clock with local partners to deploy life-saving equipment and first responders to communities across California," Newsom said Wednesday. "With more dangerous storms on the horizon, we'll continue to mobilize every available resource to protect Californians."