Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Likely
- Size
- 1.5–2.5
Yesterday's storm brought rain up to around 2500', along with strong winds and a few inches of snow in the alpine. This is going to make it tricky to predict how the weak layers of buried surface hoar will respond. Here's what we know:
- These weak layers are responsible for 2 remote triggered avalanches a week ago on Tenderfoot and we are still getting concerning results in snow tests.
- Rain reached much higher yesterday than it did during the previous storm.
- That has added extra weight to the snowpack, and the weak layers have not had much time to change at all.
What we don't know is exactly how touchy those weak layers will remain. It is likely that all of that rain helped the cause stability-wise at mid and lower elevations because the snow above the weak layers is likely now either a thick crust or a wet and incohesive slab of mushy snow. But at some point there will be a transition from that wet mush to new snow that will likely still be reactive and capable of making big avalanches.
Approach steep terrain very cautiously today. Be aware that these layers of surface hoar tend to exist in pockets, so even if you dig a pit and get a stable result you may still trigger an avalanche in a nearby slope. When these layers are the main concern, it's usually best to avoid big steep terrain, especially if there is any kind of terrain trap below.
(11/22/2025)
Buried surface hoar on the bed surface of an avalanche that was triggered last weekend.
Photo: Peter Wadsworth
