Avalanche: Boundary Creek

MacKay and Beacham

Uintas » Boundary Creek

Boundary Creek

10,200'

West

Skier

Unintentionally Triggered

Soft Slab

Persistent Weak Layer

Facets

2'

800'

900'

TLDR: Multiple large D2 remote triggers from low-angle terrain. High connectivity on West aspects, failing at the new/old snow interface. Crown depths 18"–36". Hiked back to the yurt late 2/20 and noted some collapsing while walking on the skin track in after the ridge yurt. Slept in then did our first lap around 11 a.m. We skinned through the trees to a low angle ridge to ascend, and noted widespread collapsing with long cracks propagating far away. We got to a flat spot on the ridge, where we discussed our options to ascend the last section, which had some steep sections we needed to avoid. We began making our way up again when we felt and heard a large collapse. About 250 feet away, 60 foot wide, 18"-24" deep avalanche slid down the slope. We decided to go get a look. After, we continued to the top and skied through low angle terrain back to the yurt. In the evening, our group of 4 went for one more lap along the same route. We spaced out on the way down. Skier 1 was about half way down the slope when skier 2 had an equipment malfunction so skier 3 went to help. Skier 4 then went down, a bit farther to skiers left than everyone and a little closer to the steep and open face, then he cut over to see what was going on with 2 and 3. At that moment, skier 1 radioed that there had been a large avalanche, and checked to make sure that everyone was accounted for. Skiers 2,3, and 4 did not see or hear the avalanche. The slope adjacent to the shoulder we had been skiing had avalanched, propagating full width (about 800') with a crown estimated to be anywhere between 18" to 3'. The debris pile was significant, burying and breaking a few small trees, and there were rocks and logs now exposed along the path of the avalanche, which had nearly ripped to the ground. The edge of the debris pile was no more than 300 feet from the yurt, which highlights the importance of carefully selecting terrain and being aware of what is above you even when you are "close to home". Both avalanches were remotely triggered from low angle slopes and failed on the new snow old snow interface with crowns on western slopes estimated to be in the low 30s.