Bollettino valanghe

Eastside Region

Eastern Sierra Avalanche Center
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Pericolo valanghe

Tue
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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In sintesi

In areas with shallow, variable snow cover, you could still trigger a large avalanche failing in weak snow near the ground. Continued warming means that wet loose avalanches will again be possible after the surface snow thaws. You can limit your exposure to both problems by sticking to lower-angled slopes with deep, uniform snow cover and no overhead hazards. 

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1.5–2.5

    You could trigger a dangerous avalanche near shallowly buried rocks or from the edges of steep slopes where the slab over weak snow is thin. Persistent slab avalanches can be triggered from a distance, from flatter terrain adjacent to, or below steep slopes. Failures often propagate long distances and wrap around terrain features. Where weak layers are buried more than three feet below the snow surface, signs of instability - like shooting cracks and collapsing - may be less obvious. However, the possibility of human-triggered avalanches still exists. Cautious route selection remains the most important strategy to manage this problem. Choosing travel routes with lower slope angles and no overhead hazard is a good way to limit your exposure to these types of avalanches.

    (1/28/2024)

    Northeast aspect above 11,000 feet on Mt. Olsen, Virginia Lakes.

    Photo: Clancy Nelson

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    Rollerballs and sinking into wet surface snow on steep slopes are signs that you can trigger small wet loose avalanches. Rocky chutes, treed slopes, and areas with shallow snow cover will be the most concerning. Wet debris is hard to escape and even small sluffs can be dangerous above terrain traps. The best strategy is to avoid traveling on and under steep, snow-covered, slopes as the surface thaws.

    (1/27/2024)

    Natural D1.5 wet loose avalanche in southeast couloir of Dunderberg,  Virginia Lakes.

    Photo: Clancy Nelson

Avalanche Discussion

Over the past 72 hours, small wet loose avalanches, wet surface snow, and rollerballs have been common during the warmest part of the day. Some weather stations have not reported below-freezing temperatures for 3 days. Clouds have thinned or cleared allowing the surface to refreeze on open northerly slopes where surface crusts are widespread. The snow should melt quickly again today as temperatures climb and freezing levels reach almost 12,000 feet. Warming will change the snowpack structure at all elevations. Below 9500 feet, the basal weak layers have been exposed to warm-ups earlier this season. Above 10,000 feet, persistent weak layers have not previously adjusted to above-freezing temperatures and are experiencing warming for the first time. 

The last persistent slab avalanches ran on the 24th as a result of wind loading. Forecasters in Virginia Lakes experienced a small collapse at the edge of an alpine start zone yesterday. Snowpack tests continue to highlight the layer of concern: sugary snow at the base of the snowpack.

On most aspects and at all elevations, a layer of depth hoar and basal facets is buried between 2 and 3.5 feet below the snow surface under a strong mid-pack slab. Signs of instability have become less obvious where basal weak layers are buried more than 3 feet deep. However, variations in snow depth between drainages and across slopes continue to make the likelihood of persistent slab avalanches difficult to assess.

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