Avalanche forecast

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
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Avalanche danger

Tue
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Triggering an avalanche is likely on slopes where the wind has built slabs on top of weak layers in the snowpack. Slabs failing on these weak layers in sheltered terrain are less likely but can't be ruled out entirely. Triggering very large avalanches failing on weak snow at the base of the snowpack remains a possibility and would be an almost certainly unsurvivable event.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    The combination of new snow (well over 2') and plenty of wind during last week's storm were a great recipe for building wind slabs. These slabs have had a bit of time to bond to the surfaces that they were deposited on but there are still places where you can trigger them. Yesterday, on an off-duty ski day in the Sawtooths, my partner and I intentionally triggered a few small wind slabs in steep, alpine terrain. This type of terrain is unforgiving and you would not want to be caught on the wrong side of one of these slabs. 

    In this zone, these wind slabs are most concerning where they overlap with the persistent slab problems described below. Stiff slabs on top of weak layers (those in the middle of the snowpack as well as at the base) are never a good combination. 

    ADDITIONAL DISCUSSION A crust+facet combination exists underneath last week's storm snow on slopes that directly face the sun (southern half of the compass). This layer produced a number of large, natural avalanches in this zone during the recent storm:

    •  SW Bowl of Galena Peak (photo above/right)
    • In the Boulders near Mushroom Ridge, and one
    • Behind Horton Peak in the Pole Creek drainage (photo).

    Time will tell how long this layer will be problematic, but I'll be particularly leery of slopes where this layer exists for the next bit.

    (1/8/2022) This large natural avalanche occurred in the wind-affected SW bowl of Galena Peak. It likely ran on the interface between the old snow and the recent storm snow, which consists of a facet/crust layer on some steep, sunny slopes. 10,500', SW. Photo: T. Haskins

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3

    Early season snowfall left us with a layer of weak, sugary snow at the base of our snowpack. This layer is most concerning on shaded slopes at middle and upper elevations. Chris was on Titus Ridge on Friday where he found the layer buried over 4' deep. He described the snow underneath as  "still as weak and sugary as ever."  The slide pictured at right/above, which occurred near Galena Summit, appears to have failed on this weak snow. 

    The presence of this weak snow continues to strongly influence the type of terrain that local professionals (myself included!) are willing to consider traveling in. What type of terrain are we taking off the menu? Very steep (>35 degrees), rocky slopes where the wind has created a variably thick snowpack. This snowpack variability (wind drifting in places and scouring in others) creates thinner portions of the overlying slab where triggering a slide is more likely. Triggering a wind slab or a collapsing cornice are also "good" ways to impact this weak snow.

    (1/8/2022) Natural avalanche near Titus Ridge on the divide between the Big Wood and Titus Creek. Judging by the depth, it looks to have failed on weak October snow near the ground. 9400', N. Photo: T. Haskins

Avalanche Discussion

LIFE CYCLE OF A WEAK LAYER Here at the Avalanche Center, we spend a lot of time thinking about weak layers. We live in a snow climate that is particularly good at generating layers of weak snow that linger for days and weeks. These layers don't just spontaneously appear in the snowpack, they are created when the snow is still at the surface, exposed to the environment, and then get buried by subsequent snowfall. Right now, we are dealing with a few different weak layers in the snowpack; one that has been buried for over a month and another that has been buried for just a few days. Across our region, there is a lot of variability in both the nature of these weak layers and the character of the slab overlying them. 

I'm sure that you are well aware of the layer of "October snow" that exists at the base of the snowpack. This layer has been responsible for dozens and dozens of avalanches that we've observed in the past month. We've had the benefit of a few storms worth of data to watch how this snow has behaved during loading events and dozens of field days looking at it up close. The new player in the weak layer game, which we started to bury on January 3rd, is a different story. We know this layer can produce avalanches because we've already seen a handful of them. But we don't know how it will behave going forward. 

In my personal backcountry travels, I like to take a step back when I have a high degree of uncertainty, and that is how I'm dealing with this weak layer for now. We have a good sense that it is most problematic on steep slopes that face the sun directly, where it exists as a layer of facets adjacent to a crust. Because of that, I have taken this type of terrain off my personal backcountry "menu". I'm also planning to focus much of my attention on this layer in the coming days in order to get a better sense of where it is at its worst and how it is changing over time. I'll head out the door with a hypothesis in my head, compare that to the observations that I make in the field, and update my mental model accordingly. Expectations, observations, repeat.

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