Quick report
- Aspect
- Northeast
- Red Flags
- Recent Avalanches, Wind Loading, Poor Snowpack Structure
- Elevation
- 2835 m
- Red Flags Comment
- <p>We experienced no cracking or collapsing in our travels. We jumped on some recent hard slabs on test slopes but they seemed welded in. Snow surfaces were rapidly weakening. Checked 'recent avalanches', 'wind loading', and poor structure as we were investigating the skier triggered avalanche from Sunday.</p>
Travel was from Tibble Fork to Forest Lake and back west to take a look at Sunday's skier triggered avalanche.
This steep terrain had naturalled most likely during the Christmas/NY holiday cycle but left a lot of weak faceted snow on the bed surface. Some recent new snow combined with stronger winds late week left an unstable slab of wind drifted snow in this repeater terrain. Estimate was that the original natural was 2-3' deep and 800' wide. Video below.
We observed three naturals from the holiday time period - HERE, HERE, HERE
My snow profile (above via snowpilot) was just below and adjacent to the avalanche from Sunday. HS 105cm NE facing and presented as stable; seems you'd need to find a steep rocky piece of terrain that had previously avalanches and again recently loaded.
Below crown profile from the riders left flank. Deepest part of the crown was 2'. Failure plan was 10" (25cm) from the ground on a layer of 4-6mm facets and chained depth hoar. Extended column test with propagation at this layer with 18 and 28 taps.
Loose dry fist - hard facets in the bottom portion of the snowpack. This layer (under the red line) is what was left of the bed surface.
Photo of 4-6mm depth hoar where avalanche failed. Photo below of chained depth hoar
Below profile on approach. North facing 8400' elevation with total height of snow of 43". Made of up faceted snow of varying hand hardness. Weakest snow was large grained 3-6mm dry facets near the ground.
Photo of surface hoar in a meadow on the approach
Snowpack
Provo did well with this last storm, picking up 6-10" of new snow over the weekend. This new snow is rapidly faceting and we saw many very shallow loose dry facet sluffs in Tibble Fork Canyon. This will most likely be a player as a poor interface with any upcoming storms and or/more wind loading.