Persistent Slabs
- Hochgebirge
- Waldgrenze
- Unterhalb der Waldgrenze
- Wahrscheinlichkeit
- Likely
- Größe
- 2–3
Triggering thick, meaty slabs remains likely on wind-affected middle and upper elevation slopes, and is possible in sheltered terrain. Slabs may fail on either weak, sugary facets buried 2-5 feet deep or on crusts or storm interfaces in the upper 3 feet of the snowpack.
The facets: Faceted snow is buried near the ground on W-NW-N-NE-E-SE-facing slopes at middle and upper elevations, and the facets need some time without snowfall or wind-loading to strengthen. Many large to monstrous-sized avalanches released naturally since Christmas Eve (view a list of recent avalanches and photos here). Many of these avalanches would have been unsurvivable. You're most likely to trigger destructive slides on facets near the ground 1) in windy and/or rocky areas where the snowpack depth is variable and 2) in more sheltered terrain where the snowpack depth is about 3 feet deep.
The crusts: Multiple storm interfaces and rain and temperature crusts are now buried about 1-3 feet deep. Triggering avalanches involving the crusts and interfaces (photo) is most likely on slopes where the wind drifted snow or stiffened the snow surface.
How can we manage this problem? Sadly, avoidance is still the best option to reduce your risk, especially on wind-loaded slopes. Assume the slab + potential weak layer setup exists on all slopes until you dig in the snow to prove otherwise. You may or may not experience obvious signs of instability—like snowpack collapsing or cracks shooting out from your skis or sled—before triggering an avalanche.
(12/24/2025) This very large avalanche was remotely triggered from low-angle terrain adjacent to a large alpine bowl. Spring Ck in the Boulder Mountains. NW @ 10,200'. Photo: Ben VandenBos