By Amanda Eggert EBS Associate Editor

BIG SKY – A 55-year-old male died in an avalanche north of Henderson Mountain outside of Cooke City on Sunday afternoon.

Christopher Peterson of Ketchum, Idaho, was skiing in a group of four people when a member of their party triggered an avalanche approximately 100 feet wide and 6 feet deep.

Alex Marienthal, an avalanche forecaster with the Gallatin National Forest Avalanche Center, said another member of the party was partially buried but uninjured. Marienthal said the other two avalanche center forecasters are investigating the accident today.

Marienthal said the group skied the slope at least a couple of times before it slid. According to a press release from the Park County Sheriff’s Office, members of the party located Peterson in 15-20 minutes. He was buried under approximately 5 feet of snow near the base of a tree. Two skiers from another group assisted the Peterson party.

The group’s attempts at CPR resuscitation were unsuccessful. Members of the Park County Sheriff’s Search and Rescue attempted to revive the victim with an automatic external defibrillator when they arrived, but Peterson was pronounced dead at the scene.

Marienthal said he’s not sure how far the slide carried the victim. “We know that it was through pretty dense trees and that was probably a factor in the un-survivability,” he said, adding that the avalanche center would conclude their investigation within a couple of days.

Wind loading was a factor based upon weather conditions over the weekend, Marienthal said. “There were wind gusts in the 30-40 mph range [near Cooke City] this weekend and there was quite a bit of new snow over there, almost 2 feet.”

This is the first avalanche fatality of the season locally and the second one nationally, Marienthal said. On Dec. 10, a fatal slide occurred in a backcountry area near Mount Rose Ski Tahoe, outside Reno, Nevada.

Closer to Big Sky, a snowmobiler triggered an avalanche in the Second Yellow Mule area of Buck Ridge on Dec. 10. He was fully buried and located with an avalanche transceiver by his partners, sustaining only minor injuries.

Marienthal said that slide also occurred on a wind-loaded slope with a weak layer near the ground.

The considerable amount of precipitation that fell in the Northern Rockies in October formed a hard crust and a weak layer of snow is sitting on top of it, Marienthal said. “It’s a really unstable combination with a smooth bed surface below [a layer of facets] for things to fail on, propagate and slide.”

Snow is in the forecast for the next several days, with the National Weather Service calling for 3 to 5 inches of snow in Big Sky on Thursday, Dec. 15.

An earlier version of this story reported that Peterson was skiing with six other people. New information from the Park County Sherriff’s Office states there were four people in the Peterson group. Two skiers from another group assisted the rescue party after the incident occurred.