Snowstorms: See what they look like from space 1:00

(CNN) --

A dangerous winter storm is battering Northern California with rare blizzard conditions and fierce winds, while threatening to dump up to 10 feet of snow in the mountains and disrupt travel.

In the Sierra Nevada, the storm is causing heavy snowfall, reduced visibility, downed power lines and gale-force winds of more than 120 kilometers per hour, which are expected to continue roaring through the weekend.

About half a million people are under blizzard warnings in the Mountain West, and another 6 million are under winter weather advisories across the region.

The weather service warned this Friday of “high to extreme” avalanche danger until Sunday afternoon in the Central Sierra and Great Lake Tahoe area.

Extreme snowfall and strong winds combining to produce long-lasting blizzard conditions across much of the Sierra and parts of the northern mountain ranges will mean slushy and snowy conditions, making travel “impossible,” the Weather Service warned. National.

advertising

Visibility has already dropped to almost zero in some areas, meaning it is impossible to see beyond a few feet, or at all.

The impact of the storm will not be felt in the area's largest cities, but it is making travel on major routes difficult.

A stretch of Interstate 80 was closed Friday at the Nevada state line when the California Highway Patrol reported spins and low visibility.

Amtrak canceled the Friday departure of its California Zephyr service from Chicago to San Francisco as it passes through Truckee, California, in the high country, which is under a blizzard warning through Sunday morning.

A sign warns motorists about parking restrictions as snow falls Friday in Truckee, California.

Brooke Hess-Homeier/AP

Power outages are increasing, with more than 14,000 reported in California, according to the tracking website PowerOutage.us.

The number is expected to increase dramatically as winds strengthen.

Wind watches are posted in nine Western states, covering nearly 20 million people.

The most extreme conditions are developing at higher elevations, where snowfall rates could reach 7 to 12 centimeters per hour through this Saturday, threatening road closures and increasing the risk of avalanches.

Models show nearly an additional foot of snow at high elevations this Saturday morning and blizzard conditions continuing throughout the day.

Those blizzard conditions will move into eastern Nevada this Saturday morning, and blizzard warnings are in effect Saturday morning through Saturday night.

The National Weather Service in Reno said that in addition to the huge amounts of snow in the mountains, a significant amount of snow could fall at lower elevations, “even up to 15 to 35 centimeters in the Reno-Carson-Minden corridor,” it said. the office in its forecast.