Detailed Accident Report
Submitted By: Karl Birkeland
Place: MacAtee Basin, 10 miles S. of Big Sky
Summary: Snowmobiler Survives Avalanche in Southwest Montana
Totally Buried Victim Recovered with an Avalanche Beacon
On Saturday, January 23rd, 1999 a group of 11 snowmobilers went for a ride in MacAtee Basin, which is located immediately south of Buck Ridge and approximately 10 miles south of Big Ski Area. One person was side-hilling a steep, southerly facing slope that had some mixed trees on it at about 3 pm when he triggered a sizable avalanche from the middle or toward the bottom of the slope. The slide was estimated to be about 1 to 5 feet deep and about 400 ft across, and it ran about 400 ft.
Though we have not visited the site, it probably failed on a faceted layer near the ground that was created just before, and during, a pre-Christmas cold snap in southwest Montana. This layer has been steadily gaining strength throughout our area, but weaknesses have persisted in thinner snowpack areas, and many of our southern aspects in this area have these thinner snowpacks. The snowpack in this area was apparently relatively thin since after the avalanche numerous rocks could be seen through the bed surface. In addition, a quick hitting storm dropped about 14 inches of snow (with 0.7 inches of water) at Big Sky from midnight Friday through midday Saturday. Winds during the storm were mostly light. The avalanche advisory Saturday morning warned that the avalanche danger in the mountains around Big Sky was considerable (i.e., natural avalanches are possible, human-triggered avalanches are probable) on slopes steeper than 35 degrees.
Immediately after the avalanche the group organized their rescue. All members of the party had avalanche beacons and shovels and some had probes. The victim was carried about 50 feet and was completely buried and his sled was partially buried. One member of the group had a new ARVA beacon and used it to quickly zero in on the victim's location. Meanwhile, other members pinpointed the location with probes and then started digging. They estimate that the person's head was buried about 5 feet down, and when he was dug up he was unconscious, but breathing. Estimated time of burial was 5 to 10 minutes. He was uninjured, and he quickly revived and was able to ride out. His sled was located downhill from him.
This is the third live recovery of a totally buried snowmobiler in our area in the last two years. It's nice to share these happy endings once in awhile! These folks are getting the right rescue gear and learning how to use it, and that is saving lives!
Gallatin National Forest Avalanche Center