Lawinenlagebericht

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
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Lawinengefahr

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

Large human-triggered avalanches are possible, thanks to the layers of weak snow buried in the snowpack. Recently formed wind drifts and slabs are likely to be small but may be sensitive to your weight. You can reduce your risk today by steering clear of slopes that have been affected by recent winds.

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1.5–2.5

    Several weak layers exist in the snowpack. You're most likely to trigger avalanches on weak layers that are closer to the surface, but slides on deeper weak layers remain a real possibility here. The distribution, sensitivity, and depth of these layers vary across the zone and from slope to slope.

    • Surface hoar is buried 1-1.5' deep on many shady (E-N-W) slopes. In this zone, this surface hoar layer is most problematic where recent wind loading has created a stiffer slab in the upper snowpack.
    • Older weak layers, including crusts and/or facets, and occasionally surface hoar, exist deeper in the snowpack. These are buried beneath dense, 2-4' thick slabs—making them difficult to trigger but capable of producing very dangerous avalanches. While triggering them is unlikely, it can't be ruled out in rocky, wind-affected alpine terrain. This recent persistent slab avalanche in the Pioneer Mountains exemplifies the problem (above/right, details). Slopes like these have variable snow depths, with thinner areas of the snowpack that allow us to impact deeper weak layers.

    Overlapping, variable weak layers make conditions less predictable. To reduce your risk, avoid slopes greater than about 35 degrees where the wind has shaped the snowpack. You can recognize wind-affected areas by stiffer or harder snow that is more supportive of your skis or machine and surface texture such as ripples, waves, or dunes.

    (1/24/2023) This recent large avalanche occurred on the shoulder of Duncan Ridge in the Pioneer Mountains. It appears to be a heavily wind-loaded slope that broke on a persistent weak layer. A smaller wind slab avalanche is visible further right in the image. 10,100', WSW.

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–1.5

    Today, you'll find a patchwork of wind slabs at and near the surface. A multi-day wind event this week constructed stiff, dense wind slabs. Yesterday's snowfall+wind built another batch of softer slabs on top of the older slabs, and similar slabs will continue to form today. Wind slabs will be variably reactive, and the most recent slabs are likely to be the most sensitive to your weight. Slabs are most likely in upper elevation terrain, though you may find them in exposed middle elevation terrain as well, thanks to the strength of the wind.

    I was in this Zone yesterday, and I observed widespread wind-affected snow at middle and upper elevations. I also experienced some cracking and collapsing in relatively small wind drifts along ridgelines. Be on the lookout for fresh slabs—if the snow you are moving through becomes deeper or more dense you've likely found one. Cracks shooting out from your skis or sled are a clear sign that you've found an unstable slab. Triggered slides will pick up speed quickly thanks to the stiff/dense snow underneath. Small slides can also pile up debris deeply in terrain traps like road cuts or creek beds (photo here). Consider the consequences of being knocked off your feet and sent downslope in the terrain you are in.

    (1/24/2023) This small wind slab avalanche occurred recently above the Hyndman Creek trailhead, likely as a result of the N-NW winds. As the avalanche moved downhill, it appears to have entrained loose surface snow that is becoming faceted, weak, and sugary. 7500', ESE.

Avalanche Discussion

Early season storms brought roughly equal helpings of snow across our forecast area. This helped to build a snowpack that was somewhat homogenous across the region. However, over the past month, snowfall has favored our northern and western mountains and we've seen a significant divergence in the character of our snowpacks. In a broad sense, you can lump them into two categories: shallow and deep. The Galena Summit and Eastern Mtns Forecast Zone falls into the shallow category.

3-5 feet of snow are on the ground in this zone. Weak layers buried in November and December are closer to the surface here, and impacting these weak layers with our weight remains a possibility. The prominent layer of surface hoar that was buried in January hasn't seen as much of a load in this area and in most locations you need the additional stiffness and weight from wind-loading for this layer to be a problem. 

With prominent weak layers in the snowpack, fresh wind slabs at the surface, and an ongoing trickle of snowfall, the decision to choose simpler terrain today is an easy one. The consequences of triggering avalanches can vary significantly. Triggering a small slide in terrain free of rocks and trees and terrain traps is much safer than triggering a slide in extreme, rocky, treed terrain with a terrain trap at the bottom. Spend some time thinking about snowpack complexity and the consequences of being caught in a slide as you are choosing your terrain for the day.

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