Quick report
- Cracking
- isolated
Toured from South Fork trailhead on an icy trail, then ascending towards Swiss bowl. We discussed our route multiple times and ultimately opted to skin up Swiss bowl itself, rather than the standard ridge approach, because it seemed there was too little snow to be much of a threat. We observed atrociously low snow levels, which was appreciated only by the canine members of the party. As we ascended, the snow quality proved highly variable, including a patchwork of bare tundra, 3-4” of facets, soft snow (fleeting!), and - increasingly towards the upper elevations - isolated wind slabs ranging from 1-5” thick above facets and icy crust. Multiple hand pits and several conversations about route culminated in a decision to descend early due to a small (6” long) shooting crack triggered while skinning. Skier 1 almost immediately triggered a large wind slab avalanche on their first turn, and were caught and carried for a short distance. The debris was slow-moving and skier was able to self-arrest. No dogs were harmed. All drove home somewhat chastened.
Avalanche
- Size
- D2
- Aspect
- NW
- Trigger
- AS
- Elevation
- 3600 ft
We toured about 1/2-2/3 of the way up Swiss Bowl (Peak 1201) on NW aspect to 3600’. We observed the usual cross-loading trend, but no cornices were noted at the top of swiss bowl. We expected to find a stiff supportable crust with 3-5” of snow on top (dust on crust) in the gullies since this is what had been seen in similar gullies prior to the last storm. There were numerous ribs of exposed tundra that extended to the upper ridge in several places. Given the lack of snow we toured up a series of partially exposed tundra benches, inspecting the wind-accumulated snow between benches as we went. Numerous ski pole tests, and two good jumps off the skin track on the deeper snow produced no cracking, collapsing or other motion. Several hand pits showed thin snowpack (3-12”or 10-30 cm). Basal facets overlain by a pencil hard crust, then another weak layer (bsh) overlain by a layer of denser, wind-transported snow. We noticed a thin wind slab 3-4” (7-10 cm) was locally present, but it was very stubborn and did not produce cracks or collapsing until 3600’, when we decided to go down (an isolated 6” long shooting crack was noted while skinning, which precipitated the turn-around decision). A wind-slab about 4” (~10-12cm) thick was observed at our turn-around spot, but we presumed this might be isolated like the others we observed on the way up. Skier 1 proceeded to ski down in an area with slightly deeper snow and better snow quality. On the first turn, a 4-6” (10-15 cm) soft slab avalanche broke above them (wind slab) and slid on tundra. The slide slowly carried them 10-15?ft where the skier escaped unharmed, and the slow-moving slide continued down slope. Many of the north to northwest aspects are likely wind-loaded in SoFo. We were lured in by our desperation to ski soft snow closer to home, and the inconsistent feedback from the snowpack we toured up through. The past 2 winters have been overall more stable snowpack in sofo than usual, so this may have dropped our guard. It’s thin, highly variable and touchy in places. In hindsight, we suspect the thin snowpack allowed us to believe that there wasn’t really enough snow to cause a big problem, and we felt fairly confident that the wind slabs we had found while skinning up were localized and small, since the snow surface was so constantly variable. These factors allowed us to believe we were safer than we were. Great learning moment (particularly since no one was hurt!).