Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 2–3
Buried weak layers have been producing large to very large avalanches for over a month, most of them remotely triggered. Several have snapped mature trees, and many have broken back into very low-angle terrain. Slides were becoming slightly harder to trigger before the recent storm; however, a significant load of rain and snow has been added to slopes harboring buried weak layers. This new weight will stress those layers again, and so far they’ve shown little ability to handle even a modest new load. The additional weight of a person today could be enough to tip the balance.
Managing this problem comes down to staying completely out of its reach. You might see warning signs like cracking or collapsing—or you might not. It doesn’t really matter; the structure stinks, and the consequences are high. Triggering a slide is most likely where the snowpack is thin, and the weak layer is close to the surface, such as wind-scoured slopes and those peppered with rocks. The safest approach is to avoid steep avalanche terrain altogether and give runout zones, ridge crests, and the margins of avalanche paths plenty of space.
(3/5/2026)
A view of the flank of a very large (D3) avalanche remotely triggered on February 21. The slide failed on the preserved surface hoar layer from the January drought.
Photo: Mark Dundas