Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Likely
- Size
- 2–3
I saw over 40 fresh, large, natural avalanches yesterday (Observation and Avalanche Occurrences) while scoping the mountains for slides. Some were big enough to destroy vehicles. Just east of this zone in Baker Creek, Ben and Mitch saw dozens of fresh natural avalanches, remotely triggered a couple from gentle terrain, and watched a group of snowmobilers safely trigger more avalanches remotely. South of this zone, the Soldier Mountain Ski Patrol reported a large, approximately 4-foot thick natural slide on Peak 2. Sun Valley Heil Ski staff snapped a great photo (right/below) of multiple slab avalanches in the Goat Creek area. Public and professional observers reported snowpack collapsing and cracking, even in heavily traveled areas near Galena Summit.
Recent natural and human-triggered avalanches, check. Remotely triggered avalanches, check. Snowpack collapsing, check. Terrible snowpack structure, check. That's all the bullseye data I need to figure out how to travel today; with my tail between my legs.
The natural avalanche cycle has probably run its course (for now), but triggering large persistent slab avalanches remains likely in both wind-loaded and sheltered terrain. Remotely triggering slides from below, above, and to the sides of steep slopes remains a very real possibility. Small, thin wind slab avalanches you trigger near ridgelines could "step down", failing on layers deeper in the snowpack and becoming much wider than the initial avalanche.
Think long and hard about the consequences of triggering an avalanche before riding or skiing steep slopes or playing below them today.
(1/5/2021) This large persistent slab avalanche released naturally during the Jan 4-5 storm on an E aspect near 9900' in the Goat Ck drainage (near Durrance Mtn). Sun Valley Heli Ski photo.