Avalanche forecast

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
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Avalanche danger

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Out of date — this forecast expired 6 years ago.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

Highlights

You could trigger wide avalanches up to 2 feet thick. You're most likely to trigger large slides where the wind has formed drifts in recent days. Avalanches may be triggered from gentle terrain below, above, and to the sides of steep slopes.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2

    Sunday and Monday, the weak layers of sugary, faceted snow that exist throughout this zone were likely pushed past their breaking point. Chris, Ben, and local professionals observed evidence of an impressive avalanche cycle near Banner Summit. They saw 1-2 foot thick avalanches on nearly every slope steep enough to slide in that area. Poor visibility yesterday prevented us from seeing what happened in the Sawtooths and western Smoky Mtns, but the snowpack set up and storm totals were similar to the Banner Summit zone. The snowpack will need more than a day or two to recover from the warm, wet weather this past weekend. 

    Expect the unexpected, and continue to build wide safety margins into your backcountry travel. Steer clear of steep slopes if you see cracks shooting out from your skis or sled, or if you feel the snowpack collapse or hear whumpfing noises. Persistent slab problems are difficult beasts to deal with. These types of avalanches may be triggered from gentler terrain below, above, and to the sides of steep slopes.  Pay attention to the terrain that you are in as well as the terrain that you are connected to. 

    (12/22/2020) Multiple avalanches that released on Copper Mountain in the Banner Summit Zone. These broke 1.5-2' deep on the facet layer that formed during the Nov/Dec dry spell. 8600-8700', E-NE.

  • Wind Slabs

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

    A fresh batch of wind slabs formed in the last couple of days. While these slabs should be relatively small and isolated, they could knock you off your feet or sled. In addition, these slabs are adding stress to the weak snow described above. An avalanche that starts as a small wind slab has the potential to step down to deeper weak layers buried in the snowpack, resulting in a large and dangerous avalanche.

Avalanche Discussion

Weird Weather Makes Weird Avalanches

As avalanche forecasters, we spend a lot of time thinking about uncertainty and confidence. Thinking about these things helps us to produce forecasts that are both accurate and useful for you as a reader (at least, that's the idea). On days when we have a lot of information about the snowpack and the weather is simple, we can have high confidence in how the snow will behave. When the weather is changing rapidly and we find ourselves dealing with snowpacks that are unusual, our uncertainty can be high. This is the latter. 

There is no reason to hide the fact that we have a lot of unknowns and a lot of unknowables throughout the forecast area. The widespread layer of weak, faceted snow buried in our snowpack is quite unusual, a once in a decade or two sort of thing. The warm, wet weather that we just experienced is also quite unusual for this time of year; Stanley set the record for the highest temperature seen on the solstice, breaking a record that was set over 50 years ago. Now, it's near zero degrees F and there's a little "blower powder" window-dressing on top of the snowpack. The combination of unusual weather and snowpack events basically puts us in uncharted waters. The first step in dealing with uncertainty is to acknowledge its existence.

As our abnormally weak snowpack slowly adjusts to the recent load, remember that weird weather makes weird avalanches. I'll be traveling cautiously today, building some extra safety margin into my program. 

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