Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

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

As new snow accumulates today, the avalanche danger should rise to CONSIDERABLE in near and above treeline terrain and MODERATE in below treeline terrain. Expect fragile wind slabs near and above treeline and possible storm slabs in more sheltered areas near and below treeline. Human triggered avalanches will become likely today.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1

    New snow and strong southwest winds today means another round of wind slab formation on wind-loaded N-NE-E aspects and cross-loaded NW and SE aspects in near and above treeline terrain. The size of the wind slabs that form on these leeward slopes will depend on the amount of new snow that accumulates. Wind slab avalanches could involve enough snow to bury or injure a person and some may entrain more snow in the most heavily wind-loaded areas. These wind slabs may form faster than they can bond to the existing snow surfaces and human-triggered wind slab avalanches should become likely today with some natural wind slab avalanches becoming possible.

    Use clues like recent avalanches, shooting cracks, cornices above slopes, blowing snow, ripples, drifted snow, hollow sounding snow, or other wind created surface textures to identify where wind slabs may exist and avoid those areas.   

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Rapid new snow accumulation and changing conditions during the storm may allow for some human triggered storm slab avalanches to become possible on steep slopes in sheltered near and below treeline terrain today. Most of these should remain small, but some could involve enough snow to bury or injure a person. In some isolated areas on NW-N-NE aspects, this new snow may provide enough of a slab layer for a storm slab avalanche to step down to the weak layer (facets) buried in the snowpack. In this case, these avalanches may behave more like a persistent slab and could fail after a person committed to the slope or propagate farther than expected.  

    Recent avalanche activity, human-triggered cracking, collapsing, or whumping, and/or snowpit tests can help determine where storm slabs may exist. Avoiding steep slopes with signs of instability represents a prudent choice today. Low angle sheltered slopes should provide great recreation opportunities today.  

Avalanche Discussion

* Observations around the forecast area have shown that a layer of loose weak snow (facets) exists below the recent snow. Yesterday on Trimmer Peak (South Lake Tahoe area) some skier-triggered cracking occurred on this layer. On Miess Ridge (Carson Pass area), Becker Ridge (Echo Summit area),  and Castle Peak (Donner Summit area), snowpit tests targeting this layer yielded inconsistent results with a mix of unstable results and other results. Snowpit tests on Relay Peak (Mt. Rose backcountry) did not yield unstable results.

* Small stiff wind slabs that did not extend very far downslope existed along Miess Ridge. Ski kicks on these triggered small shooting cracks. 

Regions covered