Storm Slabs
- Alpin
- Limite forestière
- Sous la limite forestière
- Probabilité
- Likely
- Taille
- 1–2
Recent avalanches: A good look around yesterday afternoon showed what was a significant natural avalanche cycle from Girdwood to Portage Valley and through Turnagain Pass in the wake of Tuesday's storm. From afar, most look to have failed within storm snow layers and are not stepping down to the December facets. That said, we were unable to get close enough to any crowns yesterday to confirm with certainty. In the past week, we have seen evidence of some avalanches that likely failed in the December facets on Pastoral and Seattle Ridge. No human-triggered avalanches have been reported recently.
Our mission yesterday was to travel above the rain/snow line during a field day on Seattle Ridge. Unfortunately, even at our high point of ~3,000', we still found evidence of a thin rain crust capping the surface. Below ~2,500', the surface was saturated, and we observed several examples of wet, storm slabs on both sides of the highway that likely avalanched during the peak of the Tuesday storm. Temperatures today look to cool only slightly, with another .4 to .6" of rain falling below ~2,000'. This wet, storm slab activity is likely to continue today. Pay particular attention to unsupported, convex slopes in the mid-elevation bands (think Tincan trees) where the additional water weight will be stressing an already wet snowpack. Even a small avalanche today will be quite heavy and difficult to escape, given how dense and saturated the storm slab is. Keep terrain choices conservative, and consider the consequences (i.e., terrain traps) if a slope does slide.
In areas above the rain/ snow line, strong winds from the east and new snow will be building fresh wind slabs and storm slabs 1-2' deep. These will be deposited on a variety of surfaces, including a recently formed rain crust up to at least 3,000'. Triggering a smaller storm slab today still has the potential to affect the deeper layer of facets that could produce a very large avalanche in connected terrain.
Wet loose: We saw some evidence of wet loose avalanches in steep terrain, below ~2,500'. These are likely to be small, but could still prove troublesome in consequential terrain.
