Two skiers were injured Sunday in a snowboarding triggered avalanche at the Squaw Valley ski resort, according to a resort spokeswoman.

Authorities said the avalanche took place around 9:50 a.m. but fortunately did not bury the two injured skiers.

A 39-year-old woman was treated and released from a Squaw Valley medical clinic with undisclosed injuries while a teenage boy was treated for a shoulder injury and taken to Tahoe Forest Hospital in Truckee.

A search by rescue dogs failed to turn up any other victims.

Resort spokeswoman Amelia Richmond said the avalanche reportedly was triggered by snowboarders.

Elsewhere in the Sierra, a string of powerful storms over the last four days has dumped a mountain of snow and provided top-notch conditions for what traditionally is one of the busiest weeks of the skiing season.

Squaw Valley reported receiving more than 3 feet of new snow between Friday and early Sunday morning, and forecasters expected another 1 to 2 feet by Monday morning.

The storms have set the stage for a busy holiday week on the slopes, Richmond said, and have assured Squaw Valley of its second largest Christmas Day snowpack since 1970.

"The conditions are phenomenal especially for those who like fresh snow," Richmond told The Associated Press. "It's an incredible setup (for the holidays), and we're looking forward to a very white Christmas."

The resort has received some 200 inches of snow so far this season, compared with nearly 250 inches of snow on Christmas Day, 2010, when the region was en route to a snowpack twice the normal average. Squaw Valley averages 450 inches of snow a year.

The heavy snowfall was expected to allow many, if not most, Sierra resorts to kick into full operation.

On Sunday, Sierra-at-Tahoe near the lake's south shore reported 44 of 46 trails and 10 of 14 lifts were open.

As much snow has already fallen this season as did by April 1 of last season when the Sierra snowpack finished about half of the normal average, said resort spokesman Steven Hemphill.

"We are extremely excited about the snow that is coming in," Hemphill told the Tahoe Daily Tribune. "It's going to make for a great powder-filled holiday for all the guests coming up."

While skiers and snowboarders rejoiced over the snow, holiday travelers in the Sierra cursed it.

Tire chains were mandatory most of the weekend on all three major trans-Sierra highways linking the Sacramento, Calif., and Reno areas: Interstate 80 over Donner Summit, U.S. 50 over Echo Summit and State Highway 88 over Carson Pass.

Storms also forced closures of the mountain portions of all three major highways at various times. Tire chains or snow tires were required on vehicles on other highways around Tahoe.

The National Weather Service was calling for a chance of snow around Tahoe every day this week.