Avalanche forecast

Banner Summit

Sawtooth Avalanche Center
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Avalanche danger

Sat
Alpine
1 · Low
Treeline
1 · Low
Below
1 · Low
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Out of date — this forecast expired 5 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Avalanche conditions are generally safe. Large avalanches are unlikely. The highest chance of triggering a large slide is on very steep, rocky, wind-affected slopes.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    2–3

    Triggering a persistent slab avalanche is unlikely but not impossible. Deeply buried, persistent weak layers (facets, facets + crusts, and isolated surface hoar) exist on nearly all slopes. Know that they are under your feet or sled. Recent warm and dry conditions are giving these layers a rest but they remain your greatest threat of triggering a large, slab avalanche. 

    You're most likely to find trouble on very steep (approaching 40 degrees), rocky, wind-affected slopes. Terrain like this is most common at upper elevations. 

    (3/5/2021) Persistent weak layers in the Banner Summit zone are unlikely to produce avalanches - but they're still there. Here, a layer of surface hoar 3' down didn't fail during a snowpack test, but sheared when the block was pried out of the column. N, 8400'.

Avalanche Discussion

For now, the danger is LOW and it'll take pronounced warming or a decent storm to change that. I find making decisions appropriate for the conditions much easier when the danger is elevated. I have a low risk tolerance when the hazards are veiled in uncertainty. For the majority of this season, sticking to safer terrain has been an easy choice. My uncertainty is primarily tied to weak snow layers buried deep in the snowpack. All recent evidence points toward improving stability, but a poor snowpack structure (strong snow over weak snow) remains. Yesterday, in the Smoky Mountains, professionals checked in on this layer, and yes, it's still there and still producing concerning snowpack test scores. Even as the danger decreases I find this structure hard to ignore, particularly where the snowpack is less than about 4' deep.

We've enjoyed anomalously cool weather over the past few days considering clear skies for this time of year. Cool weather will persist today but high temperatures will climb 10 degrees by Sunday. Here are a few things to keep in mind as we head into the weekend:

  • Wet avalanches look like they have (so far) involved only recent snow, and have remained small. If overnight temperatures start to hover near freezing, we may see larger slides gouging deeper into the snowpack. This scenario will become more likely as we head into the weekend or early next week. 
  • We observed numerous cornice failures during last week's warmup. These huge chunks of snow are more prone to sagging and failing during warm weather. They can fail much further back on a ridge than you'd expect, so give them a wide berth. 
  • You're most likely to trigger a large, slab avalanche where thinner snow cover provides better access to buried weak layers. As a whole, the snowpack is thinner and these spots are more numerous in the alpine terrain of the Boulder, the White Cloud, and the Pioneer Mountains.

Don't let good stability derail your safe travel practices. LOW danger can be a double-edged sword. The decreased likelihood of triggering a slide can lure us into more consequential terrain where even a small slide could be dangerous. If you see a wind-loaded slope or another indicator of potential instability, don't assume it's safe just because the danger is LOW.

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