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Park City Mountain Resort

SALT LAKE CITY — A winter storm sweeping over the Northern Rockies is bringing the season's first significant snowfall to Utah and hammering parts of Wyoming and Montana.

Northern Utah ski areas reported getting as much as 15 inches by early Thursday with several feet more expected in the coming days. The National Weather Service said the storm will continue into Friday, then pause briefly before another blast over the weekend.

Officials reported 100-mph wind gusts in the Wyoming Range, and said up to 46 inches of snow had already fallen in the Teton Range northwest of Jackson. In Montana, a foot of snow fell on Helena, Missoula and in the Billings area. The storm triggered avalanche warnings near Yellowstone National Park and sent temperatures plummeting below zero in places.

High winds and drifting snow closed Wyoming Highway 22 Thursday morning between Jackson and the Idaho state line. Snow was piling up in the region and could total 4 feet by Friday.

Avalanche warnings were issued throughout the Northern Rockies.

The Utah Avalanche Center advised skiers to stay out of the backcountry for at least several days. Officials said the wet, heavy snow piling up in the Wasatch mountains was almost certain to slide on steeper slopes, with or without a kick from skiers.

Another wintry blast is expected to sweep through the Northern Rockies Saturday into Sunday.

In Utah, Snowbird Ski and Summer Resort was expecting to get 5 feet of snow by Sunday, turning around an unusually dismal winter of bare coverage on the slopes.

"Powderhounds have been chomping at the bit and hit Snowbird in full force" on Thursday, Snowbird spokeswoman Emily Moench said.

In Utah, Rocky Mountain Power said winter's first major blast left as many as 10,000 customers without power overnight Wednesday, mostly in the Salt Lake valley.

The snow is mixing with rain in some areas, making driving treacherous. Slick roads forced dozens of slide-offs in Idaho and closed schools across the state. In south-central Idaho, a Twin Falls woman died Wednesday after losing control of her vehicle and swerving into oncoming traffic.

In northern Idaho, the storm dumped up to 22 inches, according to the National Weather Service.

Administrators at Lewis-Clark State College in Lewiston and the University of Idaho in Moscow shuttered their campuses as a winter storm warning remained in effect for much of the region.

In southwestern Idaho, a snow-starved ski resort above Idaho's capital city rejoiced as winter finally made its presence known in the Boise region. With nearly a foot of new snow at Bogus Basin Mountain Resort, lifts rumbled to life Thursday and marked the ski area's latest opening in its 69-year history.

Associated Press writers Bob Moen in Cheyenne, Wyo., and Jessie Bonner in Boise, Idaho, contributed to this report.