Persistent Slabs
- Hochgebirge
- Waldgrenze
- Unterhalb der Waldgrenze
- Wahrscheinlichkeit
- Unlikely
- Größe
- 2–3
We've been plagued by persistent weak layers the entire season. First by early-season facets near the ground, then by weak layers that were buried in late-January and February. Warm temperatures and a lack of loading over the past week have given these layers some time to rest, but they are still there. These weak layers still exist on most slopes, but observations from across the forecast area indicate that triggering a persistent slab avalanche is unlikely.
Even though triggering a persistent slab avalanche is unlikely, that's not the same as impossible. There's still a small chance of triggering a persistent slab avalanche on very steep (approaching 40 degrees), rocky, wind-affected slopes. Terrain like this is most common at upper elevations.
ADDITIONAL DISCUSSION: Small wind slabs formed over the weekend and will continue to grow in size with today's storm. You are most likely to find these slabs near exposed, upper elevation terrain, like ridgelines and in gullies. Though small, these slabs will be sensitive to your weight today. Be alert to the consequences of being caught in even a small slide in the terrain you are traveling in.
(3/5/2021) Persistent weak layers in the Banner Summit zone are unlikely to produce avalanches - but they're still there. Here, a layer of surface hoar 3' down didn't fail during a snowpack test, but sheared when the block was pried out of the column. N, 8400'.