California storm could bring 12 feet of snow to Sierra Nevada mountains

A blizzard warning is in effect in California's Sierra Nevada mountains as a dangerous snowstorm slams the region.

Travel in the Sierras "will be extremely dangerous to impossible" this weekend, the National Weather Service warned.

The blizzard began Thursday and will continue off and on through this weekend. The heaviest snow will be Friday and Saturday, when some areas could see snowfall rates of 3 to 5 inches per hour.

Most parts of the Sierras will see 4 to 10 feet of snowfall. The snow could reach a whopping 12 feet in the highest elevations.

The heavy snow is also targeting portions of the Cascade Mountains in Oregon and Washington.

Strong winds gusting over 60 mph are forecast to cause dangerous whiteout conditions for hours at a time. Wind alerts are in effect from California to Wyoming, including Sacramento, Las Vegas and Salt Lake City.

Yosemite National Park has closed through at least midday Sunday due to the snow and high winds.

Meanwhile, heavy rain is expected in the San Francisco and Los Angeles areas through the weekend.

In the foothills of Southern California, 1 to 3 inches of rain is possible. Southern California could see some flooding, and with the ground already heavily saturated, mudslides are also possible.

Parts of Northern California and the Northwest could see 2 to 5 inches of rain through Sunday. Flash flooding is possible.