Persistent Slabs
- Alpin
- Limite forestière
- Sous la limite forestière
- Probabilité
- Possible
- Taille
- 1–2
Recent avalanches: We saw human-triggered avalanches on Sunburst, Tincan, Seattle Ridge, Goldpan, and Super Bowl last Wednesday. There was also some natural activity on Seattle Ridge, Eddie's, and Tincan earlier in the week, during the last storm. The last reported avalanche activity occurred on Wednesday.
It's looking like we have about 12 more hours in this cold and dry holding pattern before the weather starts to get a little more active. Once that happens, the avalanche danger will rise quickly. For today, our main avalanche problem is the same as it's been for most of the week. We're still concerned with the weak layer of faceted snow buried about 8 to 10" deep on average, and up to 1 to 2' deep in wind-loaded terrain. This layer was very touchy right after it was buried, but has slowly become more stubborn as the layer of snow above it has lost cohesiveness. This has made the snowpack a little less capable of propagating a fracture across a slope, which makes it a little harder to trigger an avalanche. However, triggering an avalanche is still a very real possibility for today, and this poor snowpack structure exists across most of our forecast area.
Because this weakness is so widespread, there is not much we can do to rule out an avalanche with snowpits or tests. We should assume that if it's steep enough to slide, there is a good chance it will. The good news is that these avalanches have generally been small, and for the most part, manageable. You can avoid this problem entirely by staying out of steep terrain. If you do choose to travel on steep slopes, it will be important to avoid features that increase the consequences of getting caught in an avalanche. This includes obstacles like cliffs, rocks, or trees in the avalanche path. It also includes features that allow debris to pile up — gullies, ravines, depressions, or open glide cracks, for example. Keep in mind, even relatively small avalanches can be dangerous on larger slopes where a long ride is possible.
Avalanche danger will increase quickly as soon as we see that shift to a more active weather pattern. For now, it is looking like that won't happen until later tonight, but it will be important to pay attention if this first system arrives sooner than expected.
Dry Loose Avalanches (sluffs) are very likely in steep terrain today. These are not likely to bury a person, but similar to our persistent slab problem, they can have serious consequences in the terrain mentioned above. These can be especially concerning if you're on an ice climb in a steep gully.