Observation: Alta Periphery

Traveling throughout the backcountry near Alta for most of the day before exiting to Brighton, I saw more small to large (D1-D2) avalanches than I could count (head to the Observations page HERE to see reports on many of these). These all were soft slab avalanches of wind-drifted snow that primarily broke on the density change in the snow between the 4/1 and 4/2 storms. They predominantly were on the leeward sides of ridges, however some slides, like the one on Sunset Peak, released sympathetically mid-slope, out the wind zone and propagated widely.

Poking into the crown of 4 different skier-triggered wind slab avalanches, they all appeared to run on the interface between the 4/1 and 4/2 storms. In most areas in upper elevations (and in all crowns I looked into), this was a layer that had warmed up during the greenhousing on 4/1, then refrozen, before being buring by the snow/graupel mix on 4/2. The 4/2 storm snow was primarily a soft slab, and ran on DF and stellars on top of this crust where it existed. Despite cold temps, however, the 4/2 snow was starting to slab up in the afternoon due to solar input.

There was no notable wet activity I observed. However, as I watched wind slab avalanches peel off the mid-storm-4/1-4/2-interface, and observed the 4/2 storm snow continually slabbing up during the day with solar input despite cold temps, it is hard to not imagine wet snow avalanches becoming a real problem tomorrow as temps shoot up for the first time since the storm.