Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Likely
- Size
- 2–3
The last significant avalanche triggered on the Valentine's Day surface hoar layer was on Eddies in Tunagain Pass on Sunday, March 9th. The crown of this avalanche was 3' deep and propagated very widely in low angle terrain. Despite the lack of recent avalanche observations, avalanche conditions are still very dangerous. The potential for a person to trigger an avalanche on this layer might be decreasing over time but the consequences of being involved with one of these avalanches are severe. To manage this problem, we recommend sticking to low angle terrain and avoiding slopes that are connected to steeper terrain above.
This phase of a persistent weak layer's life cycle can be very challenging to manage because we will likely see less avalanche activity, which can give a false sense of confidence. Being patient and continuing to practice conservative decision-making are key to staying safe. Buried surface hoar is uniquely difficult to manage because it causes avalanches on low angle slopes that we typically consider safe. If an avalanche releases on terrain below you, it can pull a connected chunk of slab off an adjacent ridge or safe zone. Remote triggering an avalanche onto steeper terrain above, below, or across from where you are traveling is also common.
Other concerns today include isolated wind slabs at upper elevations, loose snow avalanches on steep slopes triggered by the sun, and cornice fall. Any of these smaller avalanches could trigger a larger avalanche on the buried surface hoar.
Glide avalanches are also still an issue and we have seen recent glide releases this week. Try to avoid traveling underneath glide cracks or expose one person at a time to minimize time underneath these unpredictable hazards.
