Summary: A group of 3 skiers descended a steep, north-facing chute that goes by the local name "Jaws" in the upper section of Days Fork, Big Cottonwood Canyon of the Wasatch Range, Utah. The first two skiers descended one at a time and tucked in beneath some cliffs in a safe spot at the bottom. When the third skier entered the slope, he triggered a large, deep avalanche that carried him down through rocks and small trees and completely buried him at the bottom. He also suffered an open tibia-fibula fracture of his left leg with quite a bit of blood loss. His partners, along another nearby group, who happened to see it from the flats below, quickly located him using avalanche transceivers and dug him out within 3-4 minutes. He was not breathing and unconscious and he began breathing on his own after they cleared the airway. He was evacuated by a medical helicopter. He was buried with his face about a foot under the surface and his hand just under the surface as well.
The skiers were very experienced, well-equipped locals in their 40's
Jaws is a steep (40 degree plus) north-facing chute that goes through a narrow passage through a cliff and terminates in small fir trees at the bottom. So it's high consequence terrain. I took the upper photo from the ridge looking down. It shows where the skiers entered the slidepath in the upper right of the photo and the skier who triggered the avalanche ended up in the small fir trees on the left of the photo. I took the second photo from the bed surface of the avalanche looking down the avalanche path. Rescuers had to carry the victim down to the landing zone in the flats below.
Typical of an early season snowpack, the base of the snowpack was depth hoar and the upper horizon of the faceted snow was very weak near-surface faceted snow that was on the surface before the latest storm. This upper faceted layer was the weakest layer of the snowpack and it was probably the one that initially collapsed causing the avalanche, but the avalanche quickly stepped down to the depth hoar layer near the ground. You can see distinct dirt streaks in the track. A very large storm with extremely high west wind over the previous days deposited a 2-foot-deep layer of very dense, moist snow, which was the slab in this case. Precipitation ended about 48 hours before the accident. The day of the accident, there was mostly clear skies with increasing high clouds and warming temperatures in advance of another snowstorm.
The avalanche probably broke on or near the near-surface faceted layer around 60 cm and then quickly stepped down to the depth hoar near the ground. There was not much snow left in the starting zone because most of it avalanched but this profile is a compilation of several small pieces of intact snow left hanging to the rocks.