Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 1.5–2.5
The Valentine's Buried Surface Hoar layer, along with weak faceted snow from the January Drought (buried on Feb 8), exists in the upper 3 feet of the snowpack. If you trigger a slab avalanche on either or both of these fragile weak layers, you will likely produce a large to very large avalanche.
Persistent Slab avalanches can release in surprising ways:
- They can be much wider than expected
- They can break above you and pull into relatively gentle terrain.
- Persistent slab avalanches can and will release on slopes that already have snowmachine or ski tracks.
- Although unlikely right now, you can trigger them remotely—from flat terrain below, above, and to the sides of steep slopes.
Specific terrain features that you should avoid:
- Rocky areas that are also convex rollovers- these areas may harbor a shallower snowpack and could be easier to trigger a persistent slab avalanche.
- Slopes on the north half of the compass that are protected from the wind but are connected to larger open slopes that may have had previous wind loading.
If you have uncertainty in managing this avalanche problem, you are in good company. The absence of obvious signs of instability, such as collapsing or whumphing of the snowpack, does not necessarily mean a slope is safe to ride. Avoidance is our top (and our only) tool when it comes to dealing with a persistent slab. Further slope scale investigation is warranted if you decide to commit to consequential terrain.
Surface Hoar has been found in protected areas on NW through SW aspects.
(3/6/2026) Photo: Victor McNeil