Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 1.5–2
Persistent weak layers have been an issue in our snowpack for a while now. Large surface hoar (1cm+) found up to 3000feet, has been buried 1-2 feet deep by recent storm snow. Minimal reactivity or signs of instability have been associated with this layer in Thompson Pass and areas to the north. We will likely see increased sensitivity on this layer with additional snow loads and stiffening of overlying snow in the near future. For today, human-triggered avalanches 1-2 feetdeep are possible below 3000 feet on specific slopes over 35 degrees. Areas that have been loaded or affected by the wind will have increased sensitivity. Cracking or settling of the snowpack while travelling will indicate you are on sensitive snow that could produce an avalanche. Buried surface hoar can take a while to gain strength, so you can expect to hear more about this layer in the future.
In the maritime zone, buried surface hoar below 3000 feet has been observed to be very sensitive due to stiffer and deeper snow. Recent rain has saturated the upper snowpack, potentially adding to stresses on this layer. For today, you can expect the hazard to be Considerable in the maritime zone, with human-triggered avalanches likely.
Windslab: Isolated windslabs and areas of windrifted snow will have increased sensitivity today. Be cautious on slopes with notably deeper or stiffer snow on the surface.
Natural slab avalanche failing on buried surface hoar, on a small terrain feature.
Benzene Alley 1/27
Photo: Gareth Brown