Snow-stranded Californians in mountain communities are desperately digging out after a "once-in-a-generation" winter storm, even as more snow was forecast for the weekend.

In the latest US wild weather, twisters touched down at the other end of the country, in Texas and Louisiana.

Forecasters warned of more severe weather in the southern Plains and into areas of Arkansas and Mississippi.

Storm systems have caused widespread power outages across the country.

On Wednesday night, California Governor Gavin Newsom declared a state of emergency for 13 counties to push the pace of disaster response and relief.

Power outages continued to affect parts of the state with more than 51,000 without power as of Thursday evening, according to tracking site poweroutage.us.

The state's popular Yosemite National Park has been closed indefinitely after record-breaking snowfall last week.

In San Bernardino County east of Los Angeles, around-the-clock snow removal is underway, but it could take more than a week to reach some areas.

The California National Guard has arrived to help with the disaster relief effort underway in the San Bernardino mountains, according to CBS News, BBC's partner network in the US.

Cal Guard helicopters were seen surveying Crestline Thursday afternoon, searching for an area to set up sites to distribute supplies for any rescue efforts, it said.

Many residents remained trapped in their homes there. The county has set up a hotline for residents dealing with issues like frozen pipes, roof problems and food shortages.

Mariam Magana and her family have been snowed in at their Crestline Airbnb for nearly a week - and their food rations have been running low, she told CBS News, the BBC's US partner.

"Our three-day vacation turned into a horrific nightmare," she said.

Their cars are buried in 7ft of snow, and they have called the county's emergency line and California Highway Patrol - but help has yet to arrive.

She said they were also concerned about access to medication after her children have had to use both EpiPens - prescribed to people with potentially serious allergies - they had available.

One resident shared photos of his nearly six-mile trek through the snow for groceries on Twitter.

To feed his family of five, he used a sled to transport the supplies.

The National Weather Service (NWS) forecasts rain and additional heavy mountain snows to return to northern California on Saturday.

The NWS also warned of widespread damaging winds, large hail, and tornadoes in the southern parts of the country.

"Flash flood will also be possible from north Texas and eastern Oklahoma into Arkansas and the mid-Mississippi Valley," the NWS said in its latest forecast.

More than 345,000 homes and businesses in Texas were without power as of Thursday evening.

The same forecast predicts record warmth will continue across portions of Florida on Friday.

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