Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

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Out of date — this forecast expired 3 years ago.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

Highlights

Yesterday's storm did not meet expectations, but it still provided enough load to make triggering avalanches more likely today. People could trigger large, dangerous avalanches in places where weak snow lurks below the surface or in places where wind-blown snow has piled up. Avalanche danger will increase as the next storm impacts the area tonight and could reach HIGH during the night. Large to very large avalanches are a concern for the next few days. Consider a plan that reduces exposure to areas in and below avalanche terrain.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2.5–3

    People triggered whumpfs and collapses in the Carson Range on the buried persistent weak layers yesterday. On the Sierra Crest, tests targeting these layers continued to produce unstable results. Even though yesterday's storm produced less snow than forecast, it still added enough new load on top of the old buried weak layers to make triggering a persistent slab avalanche more likely today. People could trigger persistent slab avalanches remotely while traveling in lower-angle terrain near or below steeper terrain. These avalanches could also break wider than expected. More snow will exist above the weak layers in wind-loaded areas, allowing for larger avalanches. A storm starting tonight will add even more load on top of these weak layers and could result in larger, more widespread avalanche activity tonight and tomorrow.

    Snowpack collapse, cracking, and whumpfing indicate an unstable snowpack. Sometimes, persistent slab avalanches occur on slopes without obvious clues, especially if you hit a trigger point where the weak layer is closer to the surface or where the overlying slab is thin. This scenario may even play out on a slope with tracks on it. Using low-angle, non-avalanche terrain not connected to steeper areas above or beside can help reduce your chances of triggering an unexpected and dangerous persistent slab avalanche.

    (1/15/2024)

    Large natural avalanche between Lincoln and Anderson Peak-thought to have occurred on Sat Jan 13.  See the size of the crown relative to the people. These kind of avalanches could occur today and will become more likely as more load piles up during the next few days.

  • Wind Slabs

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

    Even though the storm underperformed, enough new snow fell for the strong SW winds to build new wind slabs on the leeward sides of ridges, gullies, and other wind-exposed terrain features. In the southern end of the forecast area, where less new snow fell, smaller wind slabs should exist. In the northern end of the forecast area (especially around Donner Summit and Yuba Pass), where more new snow fell, larger wind slabs may exist. The winds may remain strong enough near the ridges for more blowing snow to pile up on those leeward slopes today.

    Clues like recent avalanches, cracking in wind-blown snow, blowing snow, cornices above a slope, and wind-sculpted surfaces can help identify where unstable wind slabs may exist. While using routes that bypass the wind-loaded areas in favor of more sheltered terrain can help avoid potentially unstable wind slabs, you will still have to contend with the persistent slab problem mentioned above. 

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