Bollettino valanghe

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
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Pericolo valanghe

Tue
Alta quota
4 · Forte
Limite del bosco
4 · Forte
Sotto il limite
4 · Forte
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Non aggiornato — questo bollettino è scaduto 6 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Avalanche danger will rise to HIGH today. Heavy snow and wind will overload the very weak snowpack that exists. Large natural and human-triggered avalanches will become very likely. Avoid avalanche terrain and the terrain exposed to avalanche hazard from above. Avalanches may be triggered remotely—from below, above, and to the sides of steep slopes.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Very Likely
    Dimensione
    2–3

    The weak snow that is buried in our snowpack will be pushed past its breaking point today. If you are out in the early morning hours it will feel a lot like yesterday, which was plenty dangerous. If you are out after the storm has been raging for an hour or two you will find yourself in a different world. Avalanches will become much larger and much easier to trigger as the day progresses. Strong winds will drift the new snow, creating wind slabs that help to overload the weak snow beneath. These smaller slabs will help to trigger much larger slides that fail deeper in the snowpack, producing very large and destructive avalanches.

    Today is not the day to try to thread the needle in avalanche terrain. Four human-triggered avalanches have been reported in the past four days, before the storm that will begin today. Persistent slab avalanches fail in ways that surprise even the most experienced backcountry travelers. The combination of an incredibly weak snowpack and an intense storm will produce avalanches that have you second-guessing areas that you thought were safe. I'm expecting to see slides breaking hundreds and hundreds of feet wide, wrapping around terrain features like ridges and gullies, and pulling back into flatter terrain above steeper starting zones. Avalanches may be triggered remotely—from below, above, and to the sides of steep slopes. If you are riding or skiing on a flat valley bottom you may be able to trigger a large avalanche that releases thousands of feet above you and runs down to the valley floor.

    There is only one surefire way to avoid this type of problem today: avoid avalanche terrain and terrain that is exposed to avalanche hazard from above. 

    (1/1/2021) Sun Valley Heli Ski remotely triggered this avalanche from lower angled terrain 800-1000' away. The group felt a collapse that propagated across the bowl into steeper, wind-loaded terrain. Avalanche released on a 9400', E aspect in the Western Smokys. Photo courtesy of Sun Valley Heli Ski.

Avalanche Discussion

At the Avalanche Center, we have spent the past month watching our incredibly weak snowpack react to each loading event. Since our northern zones have been favored by the storms so far, they have been the proverbial canary in the coal mine for us. The picture hasn't been pretty: small storms produced big avalanches and big storms produced widespread avalanche cycles. Even days after loading events we've seen human-triggered avalanches occurring. Almost every single avalanche we have seen this year has failed on the weak snow that developed during the fall drought. That weak snow exists everywhere that there is snow on the ground.

Today, many of our southern areas (Soldier and Wood River Valley Mtns and Galena Summit and Eastern Mtns) will be receiving the first intense load of snow that they've seen this season. The snowpack in these areas is incredibly weak and it will not be able to stand up to the weight of this new snow. In our northern areas (Sawtooths and Western Smoky Mtns and Banner Summit Area) there is already a 1-2' thick slab built on this weak snow. It may take a slightly larger load to trigger natural avalanches here but these slides will be even more dangerous and destructive because of that. We are just talking about different shades of very dangerous here.

With heavy snowfall, strong winds, and the most intense loading rates we've seen all season the picture is pretty simple: today is a day to take a few big steps back. Even very experienced backcountry travelers can be taken by surprise in these types of conditions. It can be hard to wrap our heads around the types of avalanches that will be failing during this storm. Oftentimes the problem is a failure of imagination. Try this: close your eyes and picture some of your favorite steep terrain to recreate in. Chances are that it is an avalanche path. We can learn a lot about snow and avalanches during these types of events. Mother nature will be putting on one heck of a wild show today and tomorrow, lets all stick around to see it.

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