Yesterday, a backcountry rider triggered an avalanche and was pushed into a tree causing serious injury. Human-triggered avalanches continue to occur daily. Many of those avalanches have been remotely triggered from lower-angled slopes connected to steeper slopes. In many areas dangerous avalanche conditions exist, and conservative decision-making is recommended.
There are large amounts of snow available for transport. Upper elevation winds may increase a notch this morning, blowing in the teens and gusting into the 20's or 30's at best. Keep an eye out for areas that see any additional wind-loading, and the potential for small wind slabs or additional wind-loading on the persistent slab avalanche problem.
An example of a small cornice that collapsed on Friday.
A new round of weak layers was buried on February 2nd. These weak layers consist of surface hoar and facets on most east, north, and west-facing slopes, and potentially faceted crusts on high-elevation southerly aspects. This interface is now buried 2 to 4 feet on average. In the last week, there have been daily human-triggered avalanches and more natural avalanche activity. This avalanche problem can be remotely triggered from flat terrain, or propagate widely across terrain features. Shooting cracks or collapses are a clear sign of danger, but these obvious signs of instability will not always show themselves before an avalanche releases.
There are old faceted weak layers near the ground that are more stubborn to human triggers. These dense old slabs may not give warning signs before they release; they are most commonly triggered from terrain features with shallow or variable snowpacks, or if avalanches in the upper snowpack gain enough mass to step down. This problem is generally up to D3 in size.
2/4: This avalanche on Mt. Axtell exemplifies our newest generation of persistent slabs (recent storm snow breaking on facets or surface hoar), which then stepped down and triggered older hard slabs deeper in the snowpack on old weak layers near the ground.
Late last week, the majority of our documented avalanches had occurred in the NW Mountain. Now on Friday and Saturday, we have seen the majority of recent avalanches transition to the SE Mountains. As the slab becomes stronger each day, the persistent slab avalanche problem appears to be becoming slightly harder to trigger in the NW Mountains, and as that thinner slab becomes more cohesive in the SE Mountains the same avalanche problem has become more reactive. This video highlights an area where the avalanche problem has become more difficult to trigger, but the potential consequences remain severe, while these next 4 observations are a sampling of recently human-triggered avalanches that have occurred in the SE Mountains over the last 2 days, (1,2,3,4).
In the last week, there have been 14 human-triggered avalanches that were small in size, and 2 human-triggered avalanches that were large in size. There have been other natural avalanches that were also large in size. Looking ahead, the potentially larger more destructive avalanches will continue to be located at near and above treeline elevations, and be comparatively more isolated in their distribution below treeline. How reactive those avalanches are to triggering will continue to slowly decrease, but by no means does that mean there will be an immediate end to the string of human-triggered avalanches occurring. Backcountry riders have been enjoying some lovely turns lately, and many people are having some great days. If you want to ride in avalanche terrain, it is recommended to make careful snowpack evaluations while identifying and avoiding the terrain features of concern.
The avalanche danger in the SE Mountains was bumped back to CONSIDERABLE below treeline. At below treeline elevations, the avalanche size, distribution, and travel advice fit MODERATE, while the sensitivity to triggering fits CONSIDERABLE. If we are riding the line between danger ratings, we are going to go with the higher danger rating to help catch attention and highlight the human-triggered avalanches occurring.
