Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Unlikely
- Size
- 3
Triggering an avalanche 2-4' deep down into our old PWL persistent weak layer of facets and crusts is becoming less likely in most terrain. The most recent reported avalanche into this layering was in upper Wilson Fork of Mill Creek on a steep northeast facing slope at 9600'. Although snowpits continue to show a poor structure and a "lively" interface between the strong slab over the weak facets, cracking and collapsing have become much less common. I suspect that this layering will become dormant in the days ahead. I do think it would be more likely to trigger one of these avalanches in thinner snowpack areas, such as areas of the Park City ridgeline, upper Mill Creek, Lambs Canyon, the Wasatch back, or lower canyon drainages with a much shallower snowpack. (Read more about avalanches that involve PWLs here.)
A chronological display for these backcountry (ie: not ski area) avalanches is below.