Banner Summit

Triggering a 1.5-2' thick avalanche remains possible on some slopes. Avalanches are more likely on shady slopes facing E-N-W and could occur on both sheltered mid-elevation slopes and in wind-affected terrain. Recent winds have formed thin wind drifts that are likely to be small but could be easy to trigger. 

We have variable and divergent conditions across our region. This is making our jobs as forecasters difficult, and if you recreate in multiple portions of our forecast area, it means more for you to keep track of too. Here's a rundown of how things vary across the forecast area, from north to south:

In the Sawtooths & W Smokys and Banner Summit zones, the primary player is a layer of surface hoar that was buried in early January. The majority of the recent persistent slab avalanches occurred in these areas. These zones also received the most recent snowfall, and the layer can be found beneath a stout 1.5-2' thick slab on slopes that face E-N-W. Observers continue to find this layer in snowpits, but tests are showing signs of improvement. You may be as likely to trigger an avalanche on sheltered slopes as you are in wind-affected terrain. Triggering an avalanche on older, deeply buried weak layers is unlikely (but not impossible) given the more uniformly deep snowpack.

The Galena Summit & E Mtns zone has a variable and complex snowpack. The early January surface hoar can be found buried 1-1.5' deep, but it didn't get quite enough load to be a widespread issue. The surface hoar layer remains more problematic where recent or past wind loading had created a stiffer slab in the upper snowpack. Although the surface hoar is less concerning in this zone, the older, more deeply buried weak layers are more worrisome. With a shallower snowpack than further north and west, and more rocky, wind-affected alpine terrain, there are more areas where these weak layers are closer to the surface.

Moving south to the Soldier & Wood River Valley zone, in the mountains above Ketchum and Hailey, plenty of weak snow exists but a strong slab is less common. You can avoid most avalanche hazard by staying off of wind-affected slopes where a stiffer snow surface exists. In the western portions of this zone, including the Soldiers and the mountains around Dollarhide Summit, a much more complex snowpack exists—one that has attributes of all the other zones. Avalanches occurred in the Soldiers on the early January surface hoar layer, and deeper weak layers may remain a concern similar to the Galena Summit & E Mtns zone. Throw in the recent wind events that have hammered the Soldiers, and you're likely to find a mixed bag of conditions. 

So what should you do? Snowpack weak layers are variable enough in their distribution and sensitivity that attempting a slope-by-slope assessment can be a fool's errand.  As weak layers become less reactive, it usually takes a very steep slope to trigger a slide (over about 35 degrees). Perhaps the biggest distinction you can recognize is that if you are recreating in the Sawtooths & W Smokys or Banner Summit zones, you may be as likely to trigger an avalanche on sheltered slopes as you are in wind-affected terrain. By contrast, in the Galena Summit & E Mtns and Soldier & Wood River Valley zones, wind-affected slopes are far more concerning.