Lawinenlagebericht

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
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Lawinengefahr

Tue
Hochgebirge
2 · Mässig
Waldgrenze
1 · Gering
Unterhalb
1 · Gering
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Kernpunkte

Avalanches releasing on weak layers buried 2-4 feet deep remain a possibility on very steep, rocky, wind-affected slopes at upper elevations. This problem will be most prevalent in the alpine terrain of the Boulder, White Cloud, and Pioneer Mountains. Light snowfall and moderate winds formed wind drifts at upper elevations which will be small but could be easily triggered. This problem is most likely in upper elevation terrain of the White Cloud Mountains, where the most snow fell.

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    2–3

    Early-season persistent weak layers are widespread throughout the Galena Summit & Eastern Mtns zone. In the deeper portions of this zone near Galena Summit south to Baker Creek, these layers are typically found in the bottom half of the snowpack and have been showing better stability. In the White Clouds, the weak snow near the ground is especially pronounced and produced a very large avalanche earlier in the month (see photo). In the windswept, alpine terrain of the Boulders and Pioneers, the pattern of weak snow is especially variable. You're likely to find weak layers near the ground as well as sandwiched between old wind slabs. 

    While triggering a persistent slab avalanche is generally unlikely, 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 lots of thin spots on the snowpack where weak layers are closer to the surface.

    ADDITIONAL DISCUSSIONYesterday's storm brought 4" of snow to the White Cloud Mountains, which make up the northern portion of this zone. If you are traveling in this portion of the zone, refer to the Problem Discussion and Forecast Discussion sections for the Sawtooth & Western Smoky Mtns.

Avalanche Discussion

The winter of the haves and the have nots continues. If you frequently ski or ride in this zone, you know that you are in the latter category. Yesterday's storm brought 4" of snow to the White Clouds, 1" to the Boulders and the Galena Summit area, and nothing at all to the Pioneers.  This pattern has been present for much of the winter and has "helped" to generate the ongoing persistent slab problem that we're stuck with. 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: As a slope gets steeper, gravity is pulling down more intensely on the slab. 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. In areas that are more commonly scoured, the snowpack is thinner and the weak layers are closer to the surface and easier to impact. In areas that are loaded, a stiff, dense slab of snow is stressing the weak snow underneath. Oftentimes these areas exist right next to each other, creating a scenario where likely trigger points are adjacent to meaty slabs. Not good.
  • Alpine flavor: Upper elevation terrain is typically steeper and more wind-affected than terrain lower on the mountain. In addition, this sort of terrain commonly has lots of scree piles, rocky ribs, and cliff bands. These features help to create lots of thin spots on the snowpack where weak layers are closer to the surface and easier to impact.

Take a minute to scroll through our media gallery and look at some of the deeper avalanches that we've been seeing this season. Try to identify these characteristics on slopes that have already avalanched. Then, as you are out in the backcountry, see if you can find slopes that have similar characteristics that haven't avalanched. These are exactly the types of slopes where you are most likely to encounter this problem today. The likelihood of encountering this problem isn't high, but the consequences sure are. 

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