Persistent Slabs
- Hochgebirge
- Waldgrenze
- Unterhalb der Waldgrenze
- Wahrscheinlichkeit
- Possible
- Größe
- 2–3
A layer of surface hoar buried 1 to 3’ deep is still capable of creating a large avalanche. This type of weak layer is notorious for taking months to heal which is unusual to a lot of us. Usually weak layers tend to gain strength faster but this has not been the case for this layer which has been responsible for many human triggered avalanches.
A new development is that a stout crust has formed on the surface up to 2,000’ which can make us feel safer. The truth is that we are unsure how true this is, especially if the crust is thin in some spots, doesn't freeze overnight or melts in the afternoon. Do not bet this crust will keep you safe. We still have a weak layer under a slab that is capable of triggering an avalanche.
When the snowpack is dangerous the safest option is to avoid traveling on or below steep slopes. If you do decide to venture into steep terrain, look for slopes that fan out and do not have terrain traps such as gullies or creeks where snow can pile up. People have triggered avalanches above them from relatively flat terrain. Human-triggered avalanches on this weak layer have occurred on slopes with many tracks on them so do not assume these slopes are safe.
(3/21/2025)
Overview of the two avalanches that were believe to have been triggered by a rider ascending the Headwall of Seattle Creek.
Photo: CNFAIC Staff