A group of three snowmobilers left from Big Cottonwood Canyon and traveled over Guardsmen’s Pass for a day of recreation. Once over the pass they headed south toward Claytons Peak. While playing around at the bottom of an avalanche path one of the snowmobilers triggered a large avalanche that released 400 to 500 feet above them. He was able to escape it but his friend was caught. The large avalanche carried the victim and his sled a short distance. The sled ended up completely buried and the victim was buried to his waist, uninjured. Rescue involved digging out the victim and the sled which was not damaged. The very lucky group was then able to ride back out to Big Cottonwood Canyon.
This slope is the exact location described in the daily avalanche advisory (Advisory 12-16-08) of places where you were most likely to trigger an avalanche. The weak crust/facet combination with a slab on top of it is just the set up needed to be able to trigger avalanches from a distance which is what this group did. They ignored a cardinal rule of thumb in that only one person should be on any given avalanche path at a time. Luckily, this story had a happy ending. This could have just as easily been a tragic accident ending with a fatality.
Here is a photo of the avalanche that one of the UAC observers took from near Peak 10420. He thought the avalanche had occurred naturally.