Wilson, Hardesty

Salt Lake » Big Cottonwood Canyon » Willows » West Willow

West Willow Ridge, Big Cottonwood

9,500'

East

36°

Skier

Unintentionally Triggered

Soft Slab

Persistent Weak Layer

Facets

20"

150'

400'

Pit profile and extended column test on crown near entrance of tracks. ECTP on avalanche weak layer and on the interface between decomposing fragments and facets (where, in a different location, water had pooled!). In hindsight, wish we'd dug further from the flank so we could test a weak layer that might not have been collapsed.

Mark White reported a slide in the same area on 12/23/17, so this looks to be a repeater slide. Slope wraps from East/ENE to Northeast, with the steepest sections reaching 39 degrees. Pulled out over 100' wide...On the skiers right we saw no sign of the stauchwall, to skiers left it was evident 3/4 of the way up the slope. Despite the intense southwest winds with frontal passage on Thursday, neither the slope nor the ridge above showed evidence of wind slab or heavy loading. Slide was reportedly triggered unintentionally by an experienced skier. Skier reported seeing skin track and 5 new tracks on the slope before he skied. After skiing past the convexity he triggered the slide and was able to escape to safety on skiers left, 200' below the crown. Had he been caught (or had the slide pulled out on the skinning party), results could have included battery on trees in the choke, or burial in the 2.5 meter debris pile. Toe of debris ran well onto flat ground, at 26 degrees from the crown. What caused the avalanche to pull out on the skier yesterday afternoon and not on the earlier party is a tantalizing mystery!

cool fractures in the snow even down adjacent to the runout