Persistent Slabs
- Hochgebirge
- Waldgrenze
- Unterhalb der Waldgrenze
- Wahrscheinlichkeit
- Possible
- Größe
- 2–3
Layers of weak snow are buried underneath dense, 2-5 foot thick slabs here. If you dig down you'll find facets that resemble early-season weak layers on slopes that face the sun, and crust+facet combinations on sunny slopes. These weak layers produced two remarkable avalanche cycles in our other forecast zones during the two major storms of the past week (map, list). There, we've recorded over 300 avalanches large enough to bury a person in this time, though the actual number of slides likely numbers in the thousands. Observations from this zone are limited, but indicate that these weak layers aren't quite as bad here as they are further south.
4" of SWE (snow water equivalent) was added to the snowpack here in the past 8 days. This snow has settled into a dense slab that sits perched above the weak layers below. This hefty slab makes it harder to impact the weak layers below and you may not benefit from obvious signs of instability as you move through the mountains. The first indication that the snowpack is unstable may be the very large avalanche you trigger. Avalanches may break much wider than you expect and may be triggered a distance away from the slope that slides. This includes breaking well above you on the slope you are riding or skiing. Tracks on a slope are not an indicator of stability. Avalanches can be triggered after many skiers or riders have traversed a slope.
(3/12/2023) This avalanche failed on a SE slope at 9000' in Lola Creek. Based on the aspect and the appearance of the crown, this slide likely failed on a layer of facets below a melt freeze crust.