We toured into Hyalite Peak to investigate a large, skier-triggered avalanche that occurred on Saturday (avalanche details and photos). The avalanche broke 750' wide, ran 650' vertical and broke 3-5' deep. It failed on a layer of sugary facets buried 95 cm (3 feet) deep. This layer had not been producing avalanche in the weeks prior to this slide. We measured 8.3" of snow water equivalent contained in the slab overlying the weak layer. We tested the weak layer in the eastern most part of the crown and got an ECTP26.
Additionally, we found a very weak layer of facets and surface hoar buried 1-1.5 feet deep. This had nothing to do with the large avalanche. The party reported triggering some small wind slabs near the summit, these may have been related but we don't know for sure. This layer failed with at ECTP13 and ECTP20. We looked for it again on our exit from the basin and came up empty. It is certainly something that we will look for in the coming weeks, but the primary driver of our decision-making will remain the deeper instability for now.