Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Likely
- Size
- 1.5–2.5
Recent avalanches: Several large to very large human-triggered avalanches occurred yesterday in popular locations in Turnagain Pass. Including Tincan Common, Eddie's Headwall, Main Bowl, and near the weather station on Seattle Ridge. Most, if not all, of these avalanches were remotely triggered from adjacent lower-angle terrain. In Summit Lake, there have been reports of widespread large collapses, and one observation of a natural avalanche on Tenderfoot from Saturday that was about 100 to 150' wide.
Despite the calm weather today, avalanche conditions remain very dangerous. Human-triggered avalanches about 1 to 3' deep on buried weak layers are likely. Triggering an avalanche remotely from a low-angle slope adjacent to steeper terrain is likely with this type of snowpack setup. We strongly recommend avoiding avalanche terrain and staying out from underneath avalanche paths where the runout from overhead avalanches could bury a person.
This setup was caused by the prolonged cold and clear weather in December, which formed weak layers of faceted snow. These layers have been buried and stressed by the last two storms and are now about 1 to 3' deep. The most concerning locations for these weak layers are from about 1000 to 3000', where there is an ice crust in the snowpack that has helped make the weak layers more unstable. At higher elevations, we are also seeing a weak snowpack setup, but we have limited information about recent avalanche activity due to low visibility and a lack of observations.
In addition to the widespread large human-triggered avalanches, almost every observation we have received in the past week has reported large collapses or whumphing in the snowpack. These are clear signs from the snowpack that avalanche conditions are unstable.
(1/5/2026)
This snowpack structure is a week old, but the same setup with facets under the new storm snow is still our main concern.
Photo: Marc Heifetz