Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 1–2
Wind, warmth, and light accumulations of new snow maintain the likelihood of this problem despite some signs that poor snowpack structure is healing. You can generally find these buried weak layers 1-1.5 feet down. The most likely place you'd trigger a slide is in exposed wind-loaded terrain, and weak layers can be buried even deeper here, too. New small wind slabs could be forming throughout the day in these areas as well, but only immediately adjacent to the Cascade Crest. By the afternoon, some rain along the Crest could reach middle elevation terrain. If water works its way down to buried weak layers, this could reinvigorate instability by the end of the day.
We have limited data for the zone, which creates sizeable uncertainty around an already tricky problem to manage in the backcountry. If you plan to travel near a neighboring forecast zone, consider reading that forecast as well to equip your toolbelt with more information. Either way, ease into terrain slowly. You may or may not get clear feedback from the snowpack before triggering a large slide in consequential terrain.
(3/1/2026)
Snow machine triggered large (D2) persistent slab and self extricated on 2/28. Darland Mt. NE aspect, 6700 ft.
HS- AMu-R2-D2-O @ NE, 6700' Photo: Northwest Avalanche Center