Persistent Slabs
- Alta montaña
- Límite del bosque
- Bajo el límite del bosque
- Probabilidad
- Possible
- Tamaño
- 1.5–2.5
You're most likely to trigger a large, 1-3 foot thick avalanche where a dense slab rests above weak, faceted snow and crusts. Last week's observed avalanche activity focused on N-NE-E-SE facing slopes at middle and upper elevations (near and above about 8500' in this zone). Many slopes in these areas have both thick slabs and suspect crust + facet combinations.
You can use your boots, hands, or poles to quickly check for "old snow"—crusts and/or weak, grey, sugary facets—beneath a dense slab. Steep slopes with a > 1 foot thick slab above "old snow" are the most likely places to find trouble. While slabs are larger and more widespread in obviously wind-loaded terrain, triggering an avalanche is also possible on more sheltered slopes.
Cracks shooting out from you and "whumpfing" sounds as the snowpack collapses are red flags that indicate unstable conditions. If you experience these obvious signs of instability, avoid steep slopes with similar appearances, aspects, elevations, and snowpack depths. You may be able to trigger avalanches remotely—from gentler terrain above, below, or to the sides of steep slopes.
(12/11/2025) These large avalanches released between 8,500-8,900' on NE and E aspects near Copper Mountain.