Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 1–2
Triggering large, destructive avalanches involving 1-2 foot thick slabs on weak, early-season facets near the base of the snowpack remains a possibility. The ingredients for this recipe live on all upper-elevation slopes and middle-elevation slopes on colder aspects of the compass (W-N-E). On colder slopes, an easily identifiable layer of weak, sugary facets sits underneath this slab. On more solar (SW-S-SE) aspects, the weak layer presents as a stack of facet + crust sandwiches and is more difficult to identify.
Obvious signs of instability like recent avalanches, cracking, and collapsing have all been decreasing without additional snowfall — but not disappearing. Don't forget that the weak snowpack structure still lingers. Four out of the five people in your group could ride a slope and high-five at the bottom, while rider five triggers and is caught in a slide. Slides can break well above you on the slope.
ADDITIONAL DISCUSSION: Dense small wind slabs that are reactive to your weight remain a possibility near ridgelines today. These will be small but can knock you off your feet in a consequential spot. Small avalanches can be effective triggers for slabs failing on the weak snow near the ground.