Our group of three triggered an avalanche in Upper Mill Creek today. Our first run was on south facing South Murdock Bowl and was without incident. Snow was approximately boot deep and was just enough to cover firm older snow. Our second run was further to the west, was also south facing and was where we triggered the avalanche.

At the top of the run, skier 1 (me, Andy Paradis) noted that the slope has a roll and that he had previously dug a pit in this area and found weak snow. Our first mistake was not discussing the route more carefully. It is possible to ski this slope and stay more to the west and avoid the roll or ski around it, closer to the trees. All of us have skied this slope before, including the prior weekend which probably contributed to a lack of discussion about the route. Skier 1 went first and skied the roll in an area that was actually steeper than where the avalanche was triggered but had less wind loading. At the bottom of the roll, Skier 1 paused briefly and could see that he had triggered a small wind slab perhaps 6” deep and 20 feet wide. Skier 1 then continued out of the way to lower angle terrain.

Skier 2 descended to the left of Skier 1, in an area that had more wind loading and triggered an avalanche. Skier 2 pulled his airbag was carried perhaps 300 feet.

Skier 3 was able to see that Skier 2 had triggered an avalanche, paused briefly at the top of the roll to assess the situation then skied down to Skier 2 without incident. Skier 3 arrived at Skier 2, very quickly, perhaps in less than 2 minutes. Skier 2 was buried except for the airbag and his face. The rest of his body was pinned in the snow.

After the avalanche, Skier 1 skinned back uphill to Skier 2’s position. By that time, Skier 3 had dug Skier 2 out of the snow, he stood up immediately, and reported being sore, as his knees and arms were twisted under the debris and due to the rough ride down the slope through aspen trees, but otherwise fine. Skier 2 lost 1 pole and 1 ski but we were able to find the missing ski after searching. All three skiers ascended the bed surface to look more closely at the avalanche and returned home without incident. We called Canyons Dispatch to indicate everyone was OK.

Avalanche Details

The avalanche crown was 2 feet deep at maximum, the slide was approximately 75 feet wide and ran maybe 400 vertical feet. I think this was wind slab that failed on facets and involved all of the snow from the last two weeks (which was about 2 feet). The debris included large firm chunks of snow characteristic of a firm slab and piled up fairly deep in places. The avalanche also snapped a few smaller trees and bent over others. The slope angle on the steepest part of the roll was in the low thirty degree range. The avalanche pulled back quite far into lower angle terrain. Will revisit tomorrow and collect better measurements.

Other Notes

Skier 2 reported that he could feel the airbag significantly lifting him which was somewhat surprising since the slope was relatively small and there would have not been much time for inverse segregation to occur. The bag is a bright orange color and it was possible for Skier 1 and Skier 3 to easily spot Skier 2’s location and know that he was on top.