Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Very Likely
- Size
- 1.5–2
Large avalanches breaking 1-3 feet below the snow surface will be easy to trigger today and may continue to release naturally. These slides can break hundreds to thousands of feet wide and can be triggered from long distances away from steeper slopes. Despite the poor visibility yesterday, a number of avalanches were observed in the terrain around Galena Summit, including on slopes that don't frequently produce avalanches. Expect to be able to trigger similar slides in similar terrain today.
A widespread layer of weak snow developed during the December drought and was buried by a series of storms this week. This layer exists on almost all slopes. There are several layers of surface hoar here, in addition to very weak stacks of facets and facet + crust combos. Slabs that fail on this layer will be largest, easiest to trigger, and most destructive in areas where the wind has been at work building slabs. Thanks to the strength of yesterday's wind, this includes most slopes. However, even slopes sheltered from the effects of the wind are not to be trusted with a weak layer like this.
Avalanches that fail on this layer can break into the weak snow near the ground, producing very large, unsurvivable avalanches (see Problem #2 below).
(1/11/2024) This large avalanche was remotely triggered in the Headwaters drainage. Ben and his partner on Thursday afternoon were over 100 feet away, on the opposite side of the ridge when they triggered this collapse and resulting avalanche. This avalanche ran through some very hazardous terrain and was plenty large to bury a person.