Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 2
On Sunday, a solo rider triggered this persistent slab avalanche from below and was caught, carried, but walked away clean -- Check it out, here.
Early season snow turned persistent weak layer now sits 2-4' beneath a supportable, cohesive slab that has proved troubling with recent activity and test results. Much of this weak snow sits beneath a rain crust that formed prior to Christmas, now buried under 1-2' of snow, making the riding and snowpack feel bomber under our sled, skis, or board. That being said, it's not! We are seeing fewer red flags for this avalanche problem, like cracking and collapsing, but it is still possible to trigger. All we need to do is find a shallow spot where we can punch through the slab and impact the weak layer below. See this setup for yourself as the proof is in the powder pudding -- Pull out your shovel or trench your track down and you will surely see the dense, strong slab sitting above weak, old, faceted snow near the ground.
I am paying particular attention to, and avoiding heavily wind-loaded slopes that have a very dense and supportable slab sitting atop the weak layers. Remember, we can trigger today's avalanches remotely or from a distance, meaning we don't have to be directly on the slope to trigger the slide. Persistent slab's are not manageable with ski or side-hill sled cuts, and avoidance is the go-to tool.
Shaun was out in Shingle Mill area yesterday and reported that although its heading in the right direction, our weak and faceted snow is still the main player of our avalanche hazard.