Avalanche: Birthday Chutes

Observer Name
YG/UAC Staff
Observation Date
Wednesday, November 29, 2023
Avalanche Date
Saturday, November 25, 2023
Region
Salt Lake » Little Cottonwood Canyon » White Pine » Birthday Chutes
Location Name or Route
Birthday Chutes
Elevation
10,700'
Aspect
Northwest
Slope Angle
Unknown
Trigger
Unknown
Avalanche Type
Soft Slab
Avalanche Problem
Persistent Weak Layer
Weak Layer
New Snow/Old Snow Interface
Depth
2'
Width
200'
Vertical
700'
Comments
Middle one of the birthday chutes. Entire chute went. Multiple crowns, slid to the ground level layer. Debris run all the way down to the flats. Saw a track close to the crown but it traversed back to the ridge.
Comments
Forecaster Comments: This avalanche was originally reported on 11/25/2023. The UAC forecaster team went in to look at it on November 29, 2023. Our impression was that this was a D2 (large enough to bury a person) avalanche that ran on dry facets above a crust approximately 1' off the ground. Total depth of snow adjacent to this avalanche at 10,340' was 42" (107cm) and the test results showed ECTX x 2. However, a propagation saw test PST in the dry facets above the dirt crust showed propagation to the end. There were a couple of different avalanche crown faces in this slide. There was an initial crown down off the ridge in the center of the chute, another propagating crown under the cliff band half way down, and the lower riders left flank (where it had been wind loaded) pulled out to the ground.
It was really hard to tell what the trigger may have been. We did observe at least one track in on the riders left flank. We couldn't see a track out and were unsure of the timing of the track so we did a quick beacon search on the debris pile, finding no signals. There were multiple tracks on the lower angle slopes to the west of this avalanche and we observed some signs of settlement and cracking in nearby lower angle slopes from previous days.
Coordinates