Lawinenlagebericht

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
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Lawinengefahr

Wed
Hochgebirge
4 · Gross
Waldgrenze
4 · Gross
Unterhalb
4 · Gross
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Veraltet — dieser Lagebericht ist 6 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Very dangerous avalanche conditions exist and the avalanche danger is HIGH today. Heavy snow and strong winds are overloading a very weak snowpack. 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.

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Very Likely
    Größe
    2–3

    The weak snow that is buried in our snowpack has been pushed to its breaking point. Snowfall intensity peaked overnight and moderate to strong winds picked up early this morning. Winds are drifting the 6-12" of new snow, creating thick wind slabs that are helping 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 were reported in the past five days, before the storm. 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 once thought were safe. As the skies clear, I'm expecting to see slides that have failed 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

Yesterday's storm arrived a few hours later than forecast. Snowfall intensity peaked after dark and continued until after midnight, when a cold front put an end to the heaviest precipitation. However, even though the snow stopped falling, the loading continued. Wind can load slopes many times more rapidly than snow falling from the sky and the winds are cranking right now. Why is this important? Avalanches are most likely to be triggered (both naturally and by you) during times of loading. With over a foot of new snow and strong winds there is no doubt that significant loading is occurring at this very moment. 

During this storm, our southern areas (Soldier and Wood River Valley Mtns and Galena Summit and Eastern Mtns) received the most 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 a very weak snowpack and the most intense loading rates we've seen all season the picture is simple: today is a day to take a few big steps back. Even very experienced backcountry travelers can be taken by surprise with this type of snowpack. It can be hard to wrap our heads around the types of avalanches that are possible when a uniquely weak layer of snow gets loaded rapidly. Want an example? Less than a week ago an avalanche was triggered from 1,000 feet away. Expect the unexpected and build wide safety margins into your travel plans if you choose to go into the backcountry today. 

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