Persistent Slabs
- Hochgebirge
- Waldgrenze
- Unterhalb der Waldgrenze
- Wahrscheinlichkeit
- Possible
- Größe
- 2–3
Widespread layers of weak snow can produce large avalanches here. These are buried beneath dense, 1-4 plus foot thick slabs, which makes triggering slides more difficult. These thick slabs also mean that any slide you trigger will be large and destructive. Do not expect feedback to receive obvious feedback from the snowpack today. The first sign of instability may be the large, wide avalanche that you trigger. These slides can be triggered after dozens of skiers or riders have traversed a slope. Triggered slides are likely to break far above you, making escape difficult to impossible.
Skiers remotely triggered a very large slide in this zone yesterday on Saviers Peak without receiving any warning signs. Avalanche activity during major storms of the past two weeks was widespread, occurring on all aspects. Many huge slides in this zone failed on persistent weak layers in the upper and middle portion of the snowpack. You'll find a variety of weak layers here (crusts with facets on solar slopes, and facets without crusts on shaded slopes). These weak layers have gained some strength and the likelihood of triggering a slide on them is gradually decreasing, but the consequences would be severe.
Triggering a slide is most likely in steep, rocky, open, heavily wind-affected terrain (photo at right/above). You can reduce your risk by avoiding this type of terrain.
ADDITIONAL DISCUSSION - NEW SNOW: Expect to encounter small instabilities in the new snow that falls during the day today. Small pockets of wind-drifted snow may be sensitive to your weight as you climb higher in elevation. While small, these could knock you off your feet in consequential terrain above cliffs, rocks, and trees. If the sun comes out more than forecasted, loose snow avalanches can run fast and far on slick crusts, gaining speed and mass as they rocket downhill. These smaller slides are possible triggers for the instabilities deeper in the snowpack described above.
(3/6/2024) Very large avalanche on a SE aspect above Window Lake north of Boulder Basin. Photo: Sun Valley Heli Ski