Avalanche forecast

Banner Summit

Sawtooth Avalanche Center
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Avalanche danger

Sun
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Out of date — this forecast expired 6 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Significant snowfall, wind-drifting, and warming temperatures have created dangerous avalanche conditions. Human-triggered avalanches breaking 1-2 feet thick are likely on steep slopes. While unlikely, we can't rule out triggering a very large, 4-foot thick avalanche—especially on very steep, rocky, wind-affected slopes.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    While the Banner Summit zone did not receive as much snow as further south, the storm would still be considered a major one by our normal standards. Since Tuesday night, 1.5-2' of new snow fell in this area, accompanied by strong winds on Wednesday and Thursday, then warming temperatures yesterday. This storm snow has fallen on weak old snow surfaces consisting of facets, crusts, and surface hoar. Yesterday I found a layer of surface hoar buried beneath the 16" of settled storm snow, which yielded poor snowpack test scores (see video).

    Yesterday's warming temperatures helped to consolidate the storm snow into a more cohesive slab. Storm slabs will be thicker, stiffer, and more dangerous in windier terrain. Conditions remain dangerous today—keep your slope angles in check, and pay attention to the consequences of the slopes you plan to play on.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    3

    The layer of weak, faceted snow that exists throughout our area is buried more than 4' deep in this zone. Despite being buried beneath such a thick, dense slab, the layer is showing little sign of improvement. Yesterday, I found it to be as weak and sugary as it was several weeks ago.

    It would likely take a dose of bad luck to trigger a deep persistent slab avalanche, but the flip side is that you'd need to be extremely lucky to survive it. Triggering a deep slab is more likely in very steep, rocky, and wind-affected terrain where shallow "trigger points" exist. Trigger points are spots where the slab is thinner and where your weight can more easily impact the weak layer.  You can reduce the chances of triggering one of these beasts by sticking to slopes less than 35 degrees with a more uniformly deep snowpack.  

    (1/18/2021) This very large avalanche occurred in our Banner Summit Zone. Based on the depth and appearance of the crown it probably failed on facets buried deep in the snowpack.

Avalanche Discussion

The AVALANCHE WARNINGS for the Soldier & Wood River Valley, Galena Summit & Eastern Mountains, and Sawtooth & Western Smoky Zones have been extended until 6AM Sunday.

Exceedingly dangerous avalanche conditions are widespread throughout most of the forecast area. In comparison to our periods of "normal" elevated avalanche danger, conditions now can affect people who may not normally think about avalanches—dog walkers, out-of-bounds skiers, mountain residents. The avalanche danger is such that the only safe approach is to avoid all avalanche terrain. This means avoiding being on, below, or near steep slopes—whether you're in the backcountry, taking a walk, or just past the ski area boundary rope.

If you're reading this, you likely "get it", but maybe you know someone that doesn't. Conditions are ripe for an avalanche accident. In a small town, avalanche deaths impact us all—nearly everyone is only a few degrees of separation from being an acquaintance. Please help spread the word, and if you see someone ducking the rope on Baldy, don't be afraid to speak up. Maybe you'll save a life.

Be sure to check out Scott's latest Weekend Update to catch up on all the excitement.

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