Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

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

Avalanches will become likely by the afternoon as wind blown snow piles up on open slopes, near ridges, or in gullies. On the eastern side of the forecast area large, deep avalanches that fail on old weak snow may remain possible. Conservative terrain choices and careful route planning are recommended.

Avalanche problems

  • Wind Slabs

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

    Strong SW winds during the night started piling wind-blown snow on open slopes, slopes near ridges, gullies, and other wind-exposed terrain features. These wind slabs will start out small today, but they will grow in size and extent as more wind and snow impact the forecast area. Wind slab avalanches could grow large enough to bury or injure people, especially in places that receive the most snow. They will form on top of low-density snow, and wind slab avalanches could become likely later today and tonight. Fragile cornices may also lurk above many of these slopes. 

    Blowing snow, cornices above a slope, snow drifts, and wind-created surface textures all indicate the presence of wind slabs. Route plans that give wind slabs a wide berth can help avoid getting caught in a wind slab avalanche. This planning will also steer your group into more sheltered terrain where less wind-affected snow will likely exist.

     

    (2/5/2024)

    Classic spot for a wind slab avalanche with signs of recently wind drifted snow.

    Photo: Sierra Avalanche Center

  • Deep Persistent Slabs

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

    Weak, sugary snow (facets) still exists near the bottom of the snowpack in some places on the eastern side of the forecast area. Snowmobilers triggered a persistent slab avalanche 4 to 8 feet deep near Relay Peak on Feb 5 when these old, weak layers broke.  Similar deep persistent slab avalanches may remain possible until the weak layers adjust to the load above them. If a deep persistent slab avalanche occurs, it could be large and destructive. This problem is limited to areas on the forecast area's eastern side where the snowpack had remained shallower all season.

    Deep, persistent slab avalanches surprise people since they often occur on slopes that seem stable or on slopes with previous tracks on them. In many cases, very few signs of instability exist until someone hits a trigger point where the weak layer is closer to the surface or they somehow sink deep into the snow to hit the weak layer. The only way to effectively manage this avalanche problem is to patiently wait a few more days for the deeply buried weak layers to adjust to the new snow load. When moving through areas below avalanche terrain, remember that you could trigger these avalanches from very low on the slope.

    (2/5/2024)

    Snowmobilers triggered a deep persistent slab avalanche near Relay Peak, NV on Feb 5. The reporting party estimated the crown at 4 to 8 feet deep. The debris overran at least three previous tracks on the slope.

Regions covered