Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 1.5–3
The odds of triggering large, Persistent Slab avalanches are decreasing, but the consequences remain severe.
In areas sheltered from the wind, expect to find 1-2.5 foot thick slabs. In terrain affected by the wind, you'll find 2-4 foot thick slabs. The avalanches are failing on a variety of weak layers: facets and/or surface hoar on shadier aspects, and crust+facet combinations on sunnier slopes. Large natural and human-triggered avalanches occured on most aspects in neighboring zones in recent weeks. Assume this problem exists on all upper and middle elevation slopes and on shadier, lower elevation aspects.
Some facts to help you travel safely today:
- You may or may not experience snowpack cracking or collapsing before triggering a slide. This is disconcerting.
- You may be able to trigger avalanches remotely—from flat or gentle terrain below, above, or to the sides of steep slopes.
- Avalanches could break well above you, either while you are descending or at the bottom of a slope.
(1/24/2024) This slope collapsed and then returned unstable snowpack test scores. This was a mostly wind-sheltered location. Snowpacks like this produced nearly continual collapsing. In wind-affected terrain, the slab was harder and thicker (up to 2') and more difficult to collapse. When initiated, collapses traveled hundreds of feet. Sydney Butte, Soldier Mtns, N aspect at 6,900'.