Avalanche: Highline

Observer Name
T&A Conover
Observation Date
Wednesday, March 9, 2022
Avalanche Date
Wednesday, March 9, 2022
Region
Salt Lake » Big Cottonwood Canyon » Mineral Fork » Highline
Location Name or Route
Mineral Fork
Elevation
8,200'
Aspect
Northeast
Trigger
Snowboarder
Trigger: additional info
Unintentionally Triggered
Avalanche Type
Soft Slab
Avalanche Problem
Persistent Weak Layer
Weak Layer
Facets
Depth
2'
Width
100'
Carried
1
Comments
We ascended into Mineral Fork with a plan to ski the benches of Lower and Mid East Facing Mineral and Highline areas with the knowledge of the hazard being high today. We proceeded on the skin track up the summer trail to the Highline Ridge. At the ridge, we ascended to 8200' on an E/NE slope where we unintentionally triggered a SS-AR-D1. Hard to establish a true R value as this was a pocket into trees, versus a true "path". Two caught and one carried. I (AC) was carried 20 feet and brushed by a small tree that I grabbed onto while simultaneously wrapping my knees around another. A second pulse of snow washed over me and I was able to hang on. The slide broke 20 feet above the first ascending on the track on a small bench from a small pocket of flat terrrain breaking on a slope 32 degrees in steepness. The avalanche was 100 feet wide with a crown depth of 2 feet max. While the slide broke on relatively low angle terrain the debris flushed through steeper treed terrain. It seemed as though a portion sympathetically released to the left that we chose to avoid on our uptrack based on another debris toe that was evident as we evacuated. It was of similar size and character but we did not investigate the second crown up close due to lost gear, challenging travel and potential for more unstable snow. The slide failed on FC from the mid winter drought. Rocks (apparent in photos) near crown seem characteristic of a repeater pocket but cannot be verified by slope history. Besides lost gear and the emotional rollercoaster that comes along with botched decision making we came out unscathed.
A few takeaways. The skier caught and carried (A.Conover) did not have toes locked on ascent, so gear released quickly. I was strategically positioned in some smaller brush and able to hang on for some of the first pulse of snow until I was caught. We were also well spaced to avoid multiple burial. An arrest when caught and carried was also well implemented. If I hadn't arrested, this would have been a full burial either in one of multiple large debris against trees or the terminus of the avalanche which was a couple meters deep with significant potential for trauma and difficult travel for my partner (T.Conover) whose board was split at the time of slide.
We overshot our initial uptrack plan while distracted and chatting and backtracked to our initial planned area, utilizing steeper east facing slopes that did not harbor poor structure. When we came upon a perceivably small pocket of deeper snow with poor structure, a couple key errors occurred. We had chatted about assuming poor structure and managing size of any pocket we came across. Clearly we missed the mark here. One, we did not fully appreciate the consequences of the runout and were hyperfocused on the manageability of the size of the pocket. We called it manageable before moving forward and I (AC) grabbed onto a scrubby tree in case it slid. All in all way more snow moved than we anticipated, even wrapping into a significant amount of low angle terrain-so much so that I obviously couldn't hang on. I have chatted for years about how suboptimal an incident on the uptrack would be and had my first (and hopefully last) lesson today about how true that really is.
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