Avalanche forecast

Eastside Region

Eastern Sierra Avalanche Center
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Avalanche danger

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Out of date — this forecast expired 3 years ago.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

Highlights

Today’s northerly wind may produce unstable wind deposits on aspects you might not normally expect. It remains possible to trigger large avalanches on weak, sugary snow grains at the base of our snowpack with minimal warning.  Steep, rocky slopes and areas with shallowly buried trigger points will be the most likely place you could trigger an avalanche today. Choosing slopes with slope angles lower than 30º will limit your exposure. 

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1.5–3

    Weak sugary grains of facets and depth hoar still lay at the base of our snowpack. The depth and distribution of these grains varies greatly around our forecast region. In areas where the snowpack is shallower, this layer is easier to disturb. Where it is buried deeper, it is harder to initiate a failure. However, if triggered, an avalanche may involve the whole snowpack, and could have deadly consequences. Cracking, collapsing and wumpfing are all signs of this instability. Probing the snow as you travel can help you understand how deep this layer is. It is important to avoid trigger points such as rocks and trees, convexities, and steep terrain near rocky cliffs where the snowpack may be shallower. Some of these trigger points may be buried in areas with a deeper snowpack, which makes this problem even more difficult to manage. The best way to navigate this instability is to avoid traveling on and beneath slopes greather than 30º.

    (1/17/2024)

    Profile of a trigger point for a slope scale collapse at 9,600' on a N aspect, in the Mammoth Lakes Basin. The persistent weak layer of Faceted grains bured on 1/2/24 is near the surface above the rock slab and drops deeper where the height of snow is over a meter. The snow was weaker in this area than on the wind-loaded slope I had just crossed. My weight broke into the weak layer and caused the whole slope to collapse.

    Photo: Everett Phillips

  • Wind Slabs

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

    While much of our forecast zone saw light to calm winds during the most recent storm, higher elevation peaks and specific regions saw ample wind speeds and unstable wind drifts as a result. Winds will continue to increase and shift towards the north west today, and may create unstable wind deposits on aspects that are normally scoured. With shifting winds, normal surface indicators may be a little less reliable today. Do your own localized assessments, and be mindful of terrain features such as slopes beneath ridgelines, bowls, gullies, and chutes. Don't be surpirsed to see continual signs of active loading today, especially if the winds outperform the weather forecast. 

    Blowing snow is always a good indicator of active wind loading. 

    Photo: Everett Phillips

Avalanche Discussion

Yesterday’s storm brought 3 - 10” of new snow to various areas of our forecast region! Lingering pockets of isolated storm slabs may exist today as the new snow continues to settle. With new snow and shifting winds, be on the lookout for wind slabs on aspects you don’t normally expect to see them. 

Moving through the backcountry right now may remind you of a game of mineshaft. Reactive depth hoar still remains at the bottom of our snowpack. What has changed over the last few days is the depth and distribution of this problem. This layer now sits under 50 - 130 cm of snow throughout our region. Uneven distribution of the depth of this layer between zones, or, even on the same slope, means you could unintentionally trigger an avalanche today with little warning. Land mines, aka buried trigger points, exist everywhere, and add another level of difficulty to managing this problem. Choosing terrain with slope angles less than 30º is the best way to manage this uncertainty right now.

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