Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Likely
- Size
- 1.5–2.5
Recent Avalanches: A few more avalanches released on the Valentine's Day buried surface hoar on Seattle Ridge yesterday. One was intentionally triggered by a cornice fall in warm up bowl, and another had an unknown trigger in main bowl. This week, there have been many large avalanches on this weak layer across the advisory area.
The weather should be quiet again today, but we are still very concerned about the potential for large human triggered avalanches on a layer of buried surface hoar about 1-2' deep. Field observations have shown a mixed bag of highly unstable results where the buried surface hoar exists and relatively stable results elsewhere. That is typical for this type of weak layer, and this is part of the reason it is easy to let your guard down. Persistent weak layers often show no signs of instability and can lull you into a false sense of security before producing large avalanches.
We recommend continuing to practice patience and adopt a conservative mindset by traveling on low angle slopes and being aware of the potential to remotely trigger avalanches on adjacent steeper slopes. This type of weak layer is notorious for causing avalanches on lower angle slopes than normal and can pull the carpet out from underneath you if you are on a low angle slope connected to steeper terrain below.
In addition to the persistent slabs, we could see cornice falls near ridgelines and loose snow avalanches on the surface. If the sun comes out today, natural loose snow avalanches on steep southern aspects could be a concern. Glide avalanches are also still on our radar. We recommend keeping an eye out for glide cracks and trying to avoid spending time underneath them.
(3/6/2025) Recent avalanche in main bowl that was likely remote triggered by riders on the ridge. Photo: Sean Fallon
