TRUCKEE (AP) — A storm has left up to 18 inches of snow in the Sierra Nevada and raised the hopes of skiers and snowboarders after a subpar snowpack last winter.

Frigid temperatures also have allowed ski resorts to crank up snow-making machines in advance of the Thanksgiving holiday period.

Mammoth Mountain Resort, just east of Yosemite National Park, reported Friday that the storm brought 6 to 12 inches of snow. It was the only resort open in California on Friday, a day after it began operations for the season with some 1,000 skiers and snowboarders on the slopes.

"Snow brings them out of the woodwork," Mammoth spokeswoman Joani Lynch said. "It's very nice to have an addition of natural snow for our opening this year, and it looks like it's setting up for a real nice Thanksgiving."

Boreal Mountain Resort, atop Donner Summit north of Lake Tahoe, plans to resume daily operations Saturday afternoon after receiving 8 inches of new snow. It opened for six days beginning on Oct. 26, then suspended operations due to a lack of snow.

"With this storm we hope to be up and running for the season," Boreal spokesman Jon Slaughter said, adding it was lightly snowing Friday afternoon with the resort's snow guns going at full capacity.

Northstar California resort, just north of Tahoe, reported 8 to 18 inches of new snow, while Heavenly on Tahoe's south shore received 8 to 14 inches of snow. Both resorts plan to open Nov. 16.

Just north of Tahoe, the storm brought a foot of snow to both the Squaw Valley and Alpine Meadows resorts. Squaw is set to open Nov. 21 and Alpine Meadows Dec. 7.

The snowfall caused slow going over the Sierra as tire chains were required Friday afternoon on all vehicles except four-wheel drives on Interstate 80 over Donner Summit and State Route 88 over Carson Pass. Similar controls were in effect on other highways in the Sierra.