Persistent Slabs
- Alta montaña
- Límite del bosque
- Bajo el límite del bosque
- Probabilidad
- Possible
- Tamaño
- 1–2
Snowfall during February is incrementally stressing buried weak layers that developed during the January dry spell. The character and distribution of these weak layers vary between our Northern and Southern Mountains, and subtle differences even exist within the same range. The differences reflect variations in rain-snow elevations, storm totals, aspect, and periods of warm, sunny weather. With each passing storm, the overlying slabs have gained thickness and cohesion, steadily increasing the likelihood for both human triggering and naturally occurring avalanches. After two weeks, these layers now lurk between 1 and 3 feet below the surface. Whether or not avalanches span adjacent terrain features, the depth of weak layers will likely result in larger, more dangerous avalanches if provoked.
The best way to navigate this problem is to favor southerly-facing slopes and those that are about 30 degrees without steeper hazards directly above. Mild weather in early February wetted and softened upper snowpack layers then later refroze into thicker crust layers on southerly aspects making it more difficult to impact weaker layers below. On west through north to east-facing slopes where these problematic layers are still intact, the threat is elevated. The current structure is particularly problematic because the main evidence of instability we’ve observed is lingering propagating failures in tests, but other warning signs like recent avalanches, cracking, or collapsing have been less frequent.
New snow will build on a weak surface and previously buried weak layers that have been producing propagating results in large column tests.
February 12, 2026.
Photo: Izzy Davis
