Avalanche forecast

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
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Avalanche danger

Wed
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
2 · Moderate
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Out of date — this forecast expired 6 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

The combination of strong winds, new snow, and buried weak layers are creating dangerous avalanche conditions. Sensitive wind slabs formed overnight in exposed middle and upper elevation terrain. These slabs are hazardous in their own right and are also adding stress to layers of weak snow buried in the snowpack. You can dramatically reduce your risk of getting caught in an avalanche by sticking to slopes that are sheltered from the effects of the wind.

Avalanche problems

  • Persistent Slabs

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

    Layers of weak snow can be found near the ground and in the middle and upper portion of the snowpack:

    1. Depth hoar exists near the ground on all aspects. This is the snow that we've been talking about all season long and seem to be destined to talk about for the remainder of the season.
    2. In the middle of the snowpack are several interfaces that have produced both avalanches and unstable test results in recent days. In this zone, these layers appear to be worst where they are accompanied by a crust.

    I went looking for these problems in this zone yesterday and found both of them. On Butterfield, near the mouth of Baker Creek, I found a thin snowpack with multiple buried weak layers (observation here, photo of snowpit here). These weak layers produced unstable snowpack test results and gave me no reason to want to enter consequential avalanche terrain. I also found both of these problems on Sunday, just to the south of this zone. Near Dollarhide summit, I dug snowpits on shaded slopes and those that face the sun and got poor snowpack test results in both locations (observation here, photo of snowpits here). As I continued upwards, I found a recent large, natural avalanche in a heavily wind-loaded location that appeared to have failed on a crust before stepping down to weak snow near the ground.

    You are more likely to trigger an avalanche on upper elevation, wind-affected slopes steeper than about 35 degrees. Triggering a wind slab (see Problem #2 below) could step down into these persistent weak layers, resulting in a much larger avalanche. Long story short, you can greatly reduce your risk of triggering a large persistent slab avalanche (or a wind slab avalanche for that matter) by sticking to terrain that is sheltered from the wind.

    (2/13/2021) This intentionally-triggered avalanche above Titus Lake initiated in a wind slab and then stepped down to the weak snow near the ground. While this event is a week out, similar avalanches remain possible.

  • Wind Slabs

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

    Last night, 2-4" of new snow fell in this zone, accompanied by strong winds blowing out of the W/NW. Though 2-4" of new snow isn't that much, the wind is finding plenty of other ammunition in the snow that fell over the past 10 days. Fresh slabs on exposed, upper elevation slopes will be sensitive to your weight today, and triggering one of them is likely. I wouldn't be surprised to see that one or two had failed naturally overnight in the alpine portions of this zone (White Cloud, Boulder, and Pioneer crests). Thanks to the intensity of the wind, fresh slabs will extend down into middle elevation terrain as well. Today isn't a great day to be playing up high in the alpine—you'll find better skiing in sheltered terrain anyway.

    These fresh slabs are adding weight to the layers of weak snow buried in our snowpack, and you're more likely to trigger a persistent slab avalanche (Problem #1 above) on wind-affected slopes. 

Avalanche Discussion

A DAY OF CHANGE

The past 24 hours were a transitional period for the snowpack. Over the previous 10 days, a steady trickle of snow gradually accumulated in much of our area. If you live in the Wood River Valley, this may be hard to believe, but I assure you it is true. Throughout this period, winds remained relatively light and temperatures were cool. That sounds like a perfect recipe for good skiing and riding conditions to me. Unfortunately, conditions changed significantly yesterday. Valley bottom temperatures climbed into the low 40s F and many ridgeline locations approached freezing (32F). In the afternoon, light rain was observed in several locations in the mountains north and west of Galea Summit. In addition, the wind speed increased dramatically overnight, with average speeds in the mid 20s and gusts above 50 MPH.

These three meteorologic events (warm temperatures, rain, and wind) mean that the snowpack you encounter today is different from what you might have found this weekend. Warm temperatures promote settling of the snowpack, which can add some heft to the slab of snow sitting on top of our buried weak layers. In addition, these warm temperatures combined with a dose of sun and some spits of rain introduced another crust to the snowpack in many areas. Crusts can form long-lasting weak layers in the snowpack if they are accompanied by facets (find a short video about this here). To top it all off, wind speeds increased significantly overnight. When strong winds blow they can work their way into areas that are generally sheltered, picking up the soft snow that has been hiding out there and building fresh slabs with it. As you head into the backcountry today, be alert to all of these changes within the snowpack. Its a new world every day out there. 

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