Bollettino valanghe

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
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Pericolo valanghe

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1 · Debole
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In sintesi

You could trigger an avalanche on weak layers buried 2-4 feet deep. These slides are most likely on very steep, rocky, wind-affected slopes at upper elevations. Smaller avalanches are also possible in areas of recently wind-drifted snow.

Problemi valanghivi

  • Persistent Slabs

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

    Persistent weak layers (facets and depth hoar) in the lower snowpack are widespread throughout the Galena Summit & Eastern Mtns zone. The chances of triggering a large persistent slab avalanche decrease a tiny bit each wind-free day it doesn't snow, but it remains possible in terrain with the following characteristics:

    • Steep: Slopes in prime-time avalanche terrain around 35-45 degrees.
    • Wind-affected: Heavily wind-loaded by past or recent wind events.
    • Alpine flavor: Complex terrain with scree piles, rocky ribs, and cliff bands help to create thin snow cover where weak layers are closer to the surface.

    ADDITIONAL DISCUSSIONYou may encounter isolated, small, wind slabs in exposed terrain near ridgelines. Look for these slabs below cornices and downwind of prominent terrain features. These slabs may be thicker and more prevalent in the White Clouds where more snow fell over the weekend.

Avalanche Discussion

People often ask, "what will it take before we can stop worrying about the persistent weak layers near the ground?" First off, the words "stop worrying" paint a picture that's a bit too abrupt, but I understand the question. In our Northern zones, the combination of overall deeper snow depths and time since the last significant snow load slowly brought us to the point where triggering one of these slides is very unlikely. 

In this zone, however, the weak snow near the ground is slow to gain strength and the relatively thin snowpack offers more locations to impact the weak layer. Yesterday, as I looked down into a wind-swept, northwest facing, alpine bowl, there was no part of me that thought it was a good idea to drop in. Could I have gotten away with it? Possibly, but weak near the ground, and the consequence of triggering a large slide gave me two great reasons not to try. 

For weeks, we've been warning you about the sort of terrain where you are likely to encounter this sort of problem: steep, wind-affected, and alpine. Let's take a minute to look at why these sorts of areas are more problematic.

  • Steep: Slopes in the 35-45 degree range are at the sweet spot where it isn't so steep that the snow just sluffs off, but it is steep enough for gravity to have an appreciable downward force on the snowpack. 
  • Wind-affected: The wind plays two roles to increase the likelihood of triggering slides: it thins the snowpack to provide trigger-points and thickens the snowpack to add stress to buried weak layers. These two effects can often occur on the same slope. 
  • Alpine flavor: As you move up in elevation, the terrain tends to get steeper and more wind-affected. Also, the alpine environment has lots of scree piles, rocky ribs, and cliff bands. These features help to create many areas with thinner snow cover where weak layers are closer to the surface and easier to impact.

Spend some time scrolling through our media gallery and look at some of the deeper avalanches that we've seen this season. Try to identify these characteristics on slopes that have already slid and look for commonalities in the terrain you're considering riding. 

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