Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

MODERATE avalanche danger exists at all elevations on NW-N-NE-E-SE aspects on slopes 35 degrees and steeper due to new and old wind slabs, persistent slabs, and storm slabs. Pockets of MODERATE danger exist in all other areas where small storm slabs may also exist. Human triggered avalanches are possible today.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2

    Another round of wind and snow last night means more sensitive wind slabs today. Human triggered wind slab avalanches will be possible in wind loaded areas. Most of these wind slabs should remain less than 3 ft in depth but some larger deeper slabs could exist on heavily wind loaded slopes. Wind loaded N-NE-E aspects and cross loaded NW and SE aspects in near and above treeline terrain represent the best places to find these wind slabs. Avalanches that start as failures of the most recent wind slabs could step down into deeper weaknesses in the snowpack including some lingering weaknesses within the recent snow or the near crust facets below the recent snow on slopes where they exist.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    3

    Human triggered persistent slabs will remain possible on the NW-N-NE aspects above 8000 ft. where a loose weak layer of near crust facets exist at the base of the recent snow. Last night's new snow simply added more load above this weak layer. While human triggered persistent slabs are possible today, larger triggers like the wind slabs mentioned above, cornice failures, or multiple people on a slope are even more likely to cause a failure in this layer. Any avalanches that fail on this weak layer will be large, involving all of the snow accumulated since March 25th. These kind of avalanches can fracture across longer distances and in areas that do not typically slide.

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    The storm over the last 24 hours may have allowed small storm slabs to form on non wind affected aspects. Even though most of these should remain relatively small, they could become triggers for the persistent slabs mentioned above. In addition to these small storm slabs some loose dry sluffs involving the new snow may also occur today.

Avalanche Discussion

Yesterday 3 human triggered avalanches were reported: one on Stevens Peak, one on Scout Peak, and one on Elephant's Back. All were between 1 and 2 ft. in depth and occurred on NE aspects in near or above treeline terrain. On Stevens Peak the slide caught 3 people and buried one of them completely (no injuries were reported). If more details concerning these slides becomes available, we will post them on the observations pages.

Data and observations from N-NE aspects above 8000 ft. on Rubicon Peak and Powderhouse Peak showed that the near crust facets (loose weak snow) buried below the recent snow remain weak. Snowpit tests indicated that fractures can travel along those facets once they break. Ski cuts on small wind loaded test slopes near the summit of Rubicon also resulted in some shooting cracks and small wind slabs failures that measured about 8 to 10 inches in depth.

Regions covered