Triggering an avalanche is likely on steep slopes at upper elevations, particularly where the wind has helped to stiffen the snow. These slides are more likely in the western portion of this zone where more snow has fallen (Soldier Mountains and Dollarhide area). These slides will break 1-2 feet down from the surface on a thick layer of weak snow. Avalanches may be triggered from below, above, and to the sides of steep slopes.
On Bald Mountain, and especially in the Soldiers, weather stations reported increasing NW winds overnight. Combined with abundant soft snow, the wind may have formed small wind slabs in upper elevation terrain. These may be touchy on their own, but they are also adding more weight to the persistent slab problem discussed above.
The snowpack in this zone is most similar to the snowpack in the Galena Summit and Eastern Mountains Zone. In the past two days, skiers triggered 3 (reported) avalanches in the Galena Summit area, including one that resulted in a partial burial. You can find more information about each of these slides here, here, and here. All 3 avalanches failed on the weak snow that is buried 6-24" deep in this zone. In addition to these human-triggered avalanches, several large, natural avalanches failed in the Smoky Mountains just north of this zone during the storm on Saturday (photo at right).
Your best bet for managing this problem is to avoid steep, upper elevation slopes, particularly those with recent and past wind loading. Given the nature of our snowpack, remotely triggering an avalanche from below, above, and to the sides of steeper slopes is a possibility. Be aware of the terrain you are in and the terrain you are exposed to from above.
ADDITIONAL DISCUSSIONSaturday's storm graced us with 3-8" of low-density snow in this zone. In the Soldier Mountains, moderate to strong winds transported this snow and built stiff drifts in exposed, upper elevation terrain. These slabs are likely to be small and isolated but are adding stress to the weak snow described above. Triggering an avalanche in one of these drifts may result in a "step-down" to this weak snow, creating a much larger and more dangerous avalanche.
(12/27/2020) This avalanche failed at 9,500-9,900' on a E-NE facing slope at the head of Owl Creek in the Smoky Mountains. It appears to have released near the end of the storm on Saturday, 12/26.
We are starting to see a fair bit of variability in the way our different forecast zones are behaving. However, there is an unfortunate constant across the region: a layer of very weak snow that developed during the November/December drought. The variation we are seeing between zones is driven by how deeply this snow is buried. In our northern zones (Sawtooth and Western Smoky Mtns and Banner Summit Area) this snow is buried by the 1.5-2.5 feet of snow that fell in the past two weeks. In our southern zones (Galena Summit and Eastern Mtns and Soldier and Wood River Valley Mtns) this snow is buried about half as deep.
In addition to the depth of burial, the nature of the snow above these weak facets is important. In areas where the wind has helped to stiffen the overlying snow you are much more likely to experience cracking, collapsing, and to be able to trigger an avalanche. In areas where the snow above is soft and unaffected by the wind you are less likely to see these obvious signs of instability. Bear in mind that the new, low density snow may be masking signs of previous wind loading. If the character of the snow you are traveling through is changing from soft to firm the likelihood of triggering an avalanche is increasing. Unfortunately, even in areas that are completely sheltered from the wind, triggering an avalanche involving this weak snow is possible.
I suspect most of us are familiar with the expression "out of sight, out of mind". With blue skies and blower snow, it can be easy to forget that we have built our snowpack on some of the weakest snow you can imagine. Fortunately, you don't have to imagine it—put your shovel in the snow and you can find it! Encountering this snow in person is a great way to keep it at the front of your mind. You don't have to do snowpack tests, just get in there and interact with it with your hands. Every time I dig a snowpack I'm impressed by just how "ugly" this weak snow is. We are going to be dealing with this problem for a long time. I wish that weren't the case, but I don't have any control over the snow and neither do you. We only have control over ourselves. I will continue to advise you to exercise caution in your decision making in the mountains, not because I don't want you to have a good time, but because I want you to go home safely at the end of the day.
