Ten skiers missing after Northern California avalanche

Ten back country skiers are missing and six have been found alive after an avalanche in Northern California during a powerful winter storm moving through the state.

Search and rescue crews were dispatched to the Castle Peak area, northwest of Lake Tahoe, after someone called 911 to report an avalanche with people buried on Tuesday

Ashley Quadros, a spokesperson with the Nevada County Sheriff's Office, said the six skiers located were still awaiting rescue. Quadros said the survivors were asked to shelter in place "as best they can" to wait for search and rescue ski teams reach them.

There are 46 emergency first responders trying to reach them.

The group included four ski guides with 12 clients, Quadros said.

The Nevada County Sheriff's Office received a 911 call at about 11:30am from someone reporting an avalanche with people buried, Quadros said.

The sheriff's office, the sheriff's Search & Rescue team and a crew with the California Department of Forestry and Fire Protection combed the area of Castle Peak, which is northwest of Lake Tahoe, Quadros said.

California is being walloped this week by a powerful winter storm carrying treacherous thunderstorms, high winds and heavy snow in mountain areas.

According to the Sierra Avalanche Center of the Tahoe National Forest based in Truckee, the area in the Central Sierra Nevada, including the Greater Lake Tahoe region, was facing high avalanche danger in the back country with large slides expected to occur Tuesday and into Wednesday.

The dangerous conditions were caused by rapidly accumulating snowfall piling on already fragile snow pack layers coupled with gale-force winds.

Several ski resorts around Lake Tahoe were fully or partially closed due to the extreme weather.

The resorts along highways have avalanche mitigation programs and were not expected to be at as high of a risk as the back country where travel in, near, or below the avalanche terrain was strongly discouraged, the centre said.

"It's particularly dangerous in the back country right now just because we're at the height of the storm," said Brandon Schwartz, Tahoe National Forest lead avalanche forecaster at the centre.

Experts rely on people who witness an avalanche or its aftermath to know when and where an avalanche has occurred, Schwartz said.

Castle Peak in the Donner Summit area of the Sierra Nevada, is a popular back country skiing destination. In the nearby town of Soda Springs, at least 76cm of snow had fallen in the last 24 hours, according to the Soda Springs Mountain Resort.

Forecasters said the western slope of the Sierra Nevada in northern Shasta County - including portions of Interstate 5 - and parts of the state's Pacific Coast Range could see up to 2.4 metres of snow before the storm moves through late on Wednesday.