High wind warnings blanket Sierra Nevada region in California, Nevada: See maps

The biggest snowstorm of the season is underway in portions of California and Nevada, where snow will be measured in feet, not inches. Some portions of the Sierra Nevada could see as much as 10 to 12 feet of snow by the time the storm winds down early next week.

Howling winds, already measured at over 100 mph in some spots, will add to the weather misery for the people who live in the affected areas.

As of Friday, more than 500,000 people in the two states live where a blizzard warning was in effect, the National Weather Service said.

Storm impacts

Forecasters say the winter storm will cause "whiteout blizzard conditions" and travel will be "extremely dangerous to impossible."

The storm will not only close major roads in the passes but may bury and isolate communities for an extended time, AccuWeather meteorologists warn.

The combination of heavy snow and high winds is likely to lead to power outages that could take days if not weeks to resolve in isolated areas, AccuWeather said.

Backcountry avalanche warnings were in place around Lake Tahoe and Yosemite National Park stretching down to Mammoth Lakes.

At Yosemite National Park, visitors were told to leave the park as soon as possible – no later than noon Friday. The park is closed at least through noon Sunday, with the possibility that could be extended, park officials said on social media.

Weekend snowfall could push Sierra totals above average

Snowfall is often measured by water year, which is Oct. 1 to Sept. 30. Here's how this water year compares with the median and last year's record-breaker:

While this year's snowfall is not close to last year at the same time, there's still a chance the totals could be above average. The Tahoe region saw ⁠19.1 inches of snow in a 24-hour period from Thursday morning to Friday morning. "With the largest part of the storm still ahead of us and only being 38 inches from the March 4 average of 270 inches, we have a significant chance of getting to average snowfall for that date or ending up above it," said Andrew Schwartz, lead scientist and manager at the Central Sierra Snow Laboratory, a University of California, Berkeley field research station at Donner Pass in California's Sierra Nevada.

There's also promise in the future after all the snow melts. "We're already at 102% of the water contained in the snowpack after starting the year in January at only 28%, that is promising for the water supply this year," said Schwartz.

'A legitimate blizzard'

“This will be a legitimate blizzard,” University of California, Los Angeles climate scientist Daniel Swain said during an online briefing Thursday.

Officially, the National Weather Service defines a blizzard as a storm that contains large amounts of snow or blowing snow, with winds over 35 mph and visibilities of less than 1/4 mile for an extended time (at least 3 hours).

Precautions while driving in winter weather

Driving in snow can be treacherous. Here’s what to do if you get stranded while driving in a winter storm:

• If you get stuck and can't dig out, stay with the vehicle and don't walk outside in severe weather. 
• Keep a dome light on because it uses a small amount of electricity.
• Attach a brightly colored cloth to the car window. 
• Conserve gas by turning the engine on periodically to warm the car. 
• Make sure the tailpipe is clear of snow.

Contributing: The Associated Press

SOURCE NOAA, National Weather Service, AccuWeather, UC Berkeley Central Sierra Snow Lab and Paste BN research