California faces new threat of heavy snow, rain and floods that could put lives in 'great danger'

California is facing a fresh battering from severe weather this weekend, with a winter storm expected to bring heavy snow, rain and the threat of floods to parts of the state, potentially putting "lives and property" in "great danger," forecasters have warned.

The storm is expected to affect the West Coast, particularly California, through Friday, bringing a "burst of heavy precipitation," the National Weather Service said.

The weather service’s Weather Prediction Center has issued a high risk of excessive rainfall over California through Saturday morning, with severe, widespread flash flooding expected with the storm.

“Areas that normally do not experience flash flooding will flood,” the weather service said. “Lives and property are in great danger from Friday into Saturday morning,” it warned.

As little as 6 inches of moving water can easily knock a person off their feet, while a foot of water has the force to sweep a car away, the San Luis Obispo Office of Emergency Services warned residents of the Central Coast Friday.

"Remember, do not walk, swim or drive through flood waters and avoid non-essential travel today," the agency said.

The California Department of Transportation on Friday also urged state residents to check their local weather before stepping outside this weekend.

The department cautioned drivers to be "prepared for delays and carry extra food, water, blankets and other essentials, and pack cellphone chargers."

An “atmospheric river” already began moving into California on Thursday, raising the risk of floods, forecasters and other officials said.

“With the abundant rain coming from these atmospheric rivers, we will see flood impacts again,” Michael Anderson, the California state climatologist, said in a news briefing Thursday. He described some of the expected precipitation totals as “astounding.”

At least 10 rivers are expected to exceed their flood stages, according to the California Nevada River Forecast Center as of early Friday.

Heavy rain and high snow levels are likely across parts of the state, with warm air associated with the storm expected to see rain falling on existing snowpacks up to 8,500 feet, the weather service said.

The highest snow levels and heaviest rainfall are expected to hit central California, with "considerable flooding impacts" possible across parts of the central coast and the San Joaquin Valley, it said.

"Rain and snowmelt will lead to flooding," it warned, adding that the most significant snowmelt and overall flooding threat is expected below 5,000-foot elevation in areas with shallow snowpack. "Creeks and streams in the foothills of the Sierra Nevada will be most vulnerable to flooding from rain and snowmelt," it said.

Heavy wet snow is also expected at higher elevations, with parts of Northern California and the Sierra Nevada expected to see heavy, wet snow that could make travel difficult.

The threat of excessive rainfall is expected to drop significantly Saturday, with the weather prediction center warning of a "marginal risk of excessive rainfall" over parts of California from Saturday into Sunday morning.

"The associated heavy rain will create localized areas of flash flooding, affecting areas that experience rapid runoff and burn scars," the weather service said.

The storm is one of a series of systems expected to batter the state in March, prompting California Gov. Gavin Newsom to declare a state of emergency Wednesday to expand the state’s storm response and relief efforts.

Last week, Newsom proclaimed a state of emergency in 13 counties amid brutal storms. The governor activated the California Guard and the State Operations Center to deliver support to county-led emergency response efforts and to help coordinate mutual aid from neighboring areas.

The latest state of emergency will expand the state efforts to 21 more counties, including, "Butte, El Dorado, Fresno, Humboldt, Imperial, Inyo, Lake, Mendocino, Merced, Monterey, Napa, Placer, Plumas, Sacramento, San Francisco, San Mateo, Santa Clara, Santa Cruz, Stanislaus, Tuolumne and Yuba," according to a news release from Newsom's office.

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

The storm is expected to move out of the Rockies and onto the Plains, bringing showers and severe thunderstorms over parts of the Southern Plains and the Lower Mississippi Valley.

"The hazards associated with these thunderstorms are frequent lightning, severe thunderstorm wind gusts, hail, and a few tornadoes," the weather service said.

The northern half of the system is expected to bring heavy snow to parts of the northern Plains on Friday, as well as over parts of the upper Mississippi Valley on Saturday. Rains are also expected to develop over parts of the middle Mississippi Valley, with snowfall expected to make its way to the Great Lakes by Sunday.

The severe weather in California comes after a powerful winter storm that brought blizzard conditions and several feet of snow to the Southern California mountains in late February.

The heavy snowfall isolated communities and left some residents trapped in their homes. Wrightwood, a community of around 4,700, saw around 50 inches of snow, or a little more than 4 feet, according to the weather service.

Some mountain highways had just begun to reopen this week after being closed for more than 10 days.