Boletín de aludes

Eastside Region

Eastern Sierra Avalanche Center
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Peligro de aludes

Wed
Alta montaña
3 · Notable
Límite del bosque
3 · Notable
Bajo el límite
2 · Moderado
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Desactualizado: este boletín caducó 3 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

You could trigger a very large avalanche near shallow rocky areas, on steep slopes with variable snow cover, and from the edges of stiff wind-drifted slabs. Low-angled slopes with deep, uniform snow cover are a safer alternative as the snowpack continues to adjust to recent heavy loading. Approach recently loaded and newly snow-covered terrain with a conservative mindset and assess the snow carefully. 

Problemas de aludes

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    2–3.5

    Persistent weak layers at the base of the snowpack are still adjusting to stress from the most recent storm. Periods of incremental loading, like we’ll see today, have produced large natural avalanches for the past month. While natural avalanche activity will be less likely today, the chances of human-triggered avalanches remain elevated. In areas where the snowpack is consistently deeper and the overlying slab is stronger, signs of instability such as cracking and collapsing may be absent or inconsistent. Persistent slabs can be triggered from flatter terrain below or adjacent to steep slopes. They can break around terrain features and connect multiple start zones. You are more likely to trigger a dangerous avalanche in areas with variable snow cover: near shallow rocky areas, complex terrain, convexities, and high shady slopes north and south of Mammoth that held snow in December.

    Large persistent slab avalanches in Mammoth Rock Bowl and near the Poop Chute that failed naturally overnight on 2/4.

    Photo: Steve Mace

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–2.5

    Strong ridgetop winds drifted snow onto leeward terrain through yesterday. These stiff, textured slabs may be harder to identify as they get covered by a few inches of light new snow. If winds outperform the forecast today, small fresh slabs may develop in the most favored areas. You'll find them on the leeward sides of ridgelines, the sidewalls of alpine couloirs and gullies, and in steep forest openings. You can trigger older, harder slabs from the edges where they’re thinner. Hollow-sounding drifts, shooting cracks through stiff or textured surface snow, and the snowpack collapsing under your weight are indications that you have found unstable wind slabs. Keep in mind that even a relatively small wind slab avalanche breaking in the upper snowpack may be enough to step down to persistent weak layers near the ground, creating a larger avalanche involving the full depth of the snowpack.

    (2/5/2024)

    Small explosive triggered storm slabs in wind-drifted terrain on Wilson Butte above Highway 395. This mitigation work was done around 10 am on 2/5.

Avalanche Discussion

Many large to very large natural and explosive-triggered avalanches broke in weak old snow near the ground overnight Sunday and on Monday morning. Explosives used above Highway 395 resulted in small avalanches in wind-drifted terrain late yesterday morning. 

As people branched out into areas that have recently developed enough coverage to ride yesterday, they experienced collapsing and cracking in the upside-down storm snow and in weak snow near the ground. Those are direct warning signs that you can trigger an avalanche. Carefully assess the snowpack, or use simple terrain to give yourself a wide margin for error if you explore areas that have seen little traffic this season. Think about whether those slopes held snow earlier this season.

On slopes that held snow in December, avalanche activity over the past 48 hours has occurred on a layer of depth hoar buried between 3 and 8 feet below the snow surface under a strong mid-pack slab. Limited coverage this season had previously kept large avalanches from running into lower elevations. Plenty of new snow has accumulated in the tracks and runouts of northerly avalanche paths. So, avalanches releasing above treeline can run further into the terrain below.

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