Persistent Slabs
- Alta montaña
- Límite del bosque
- Bajo el límite del bosque
- Probabilidad
- Likely
- Tamaño
- 2–3
Recent Avalanches: Two days ago there were two human triggered avalanches on Seattle Ridge that failed on buried surface hoar, one of them intentionally triggered by cornice fall. There were also multiple natural avalanches observed from Taylor Pass. This week many natural and human triggered avalanches have been reported across the advisory area.
We are still very concerned that someone could trigger a large avalanche on a layer of surface hoar buried 1 to 3’ deep. There are three reasons why we feel extra cautious and are making conservative travel decisions:
- There have been many large human triggered avalanches on this layer between 1,500 and 3,000’ and some above 3,000’.
- Most of these avalanches have been remotely triggered meaning you can be traveling on low angle slopes and trigger a large avalanche on a slope above you or on an adjacent slope. Surface hoar is also known to trigger avalanches on lower angle slopes.
- Spooky distribution and test results: This layer is widespread at mid elevations but harder to find at upper elevations. You may not find it on the slope you are on then travel another 100’ and trigger an avalanche. Snow tests have produced stable and very unstable results. This type of weak layer is known to produce stable results and give the false sense that the slope you are on is safe then produce a large avalanche.
Many large collapses were observed yesterday towards the south end of Turnagain Pass which is another sign that the snow is unstable. The big picture based on the evidence is that we have a buried weak layer that has been found guilty of triggering many large avalanches on multiple aspects and elevations. So what do we do about it? The safest option is to avoid traveling in or below avalanche terrain. Make conservative decisions today which means not trying to outsmart the problem so we can get home safe and sound.
Other hazards to look out for are cornices falling from ridgelines which could trigger an avalanche above you. Loose snow avalanches may begin to avalanche naturally on steep sunny slopes if the sun comes out. A large glide crack opened recently on Seattle Ridge which is telling us that more may follow suit. Spend as little time under these as possible or avoid them altogether as they can open at any time creating large glide avalanches.
