Bollettino valanghe

Eastside Region

Eastern Sierra Avalanche Center
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Pericolo valanghe

Wed
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 2 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

It remains possible to trigger a large slab avalanche breaking on buried weak layers 3-6 feet below the surface. Smaller, unstable slabs of wind-drifted snow may exist near ridgelines and in confined gully features. Conservative terrain choice is the best way to manage the hazard.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3.5

    Persistent Slab avalanches are more sensitive to a person in the southern half of the forecast area and at lower elevations where the new slab is thinner (~1 meter). At higher elevations, particularly from Mammoth north, the new slab is thicker (~1.5-2 meters), and feedback may be unreliable.  A very large avalanche could be the first sign a slope is unstable. Keep In mind that a smaller wind slab avalanche, or the weight of a person in a rocky area with shallower snow cover, could be all that is needed to trigger an unsurvivable avalanche.

    Managing persistent slabs is difficult. It requires patience and deliberate terrain choice. They may be triggered remotely—from flatter terrain adjacent to steep slopes and from terrain people may typically think of as safe. Persistent slabs often propagate widely and in unpredictable ways. Tracks on a slope do not mean that it’s safe. Shooting cracks and collapses are clear warning signs of the problem. However, feedback is often irregular. The best option is to minimize your exposure to steep terrain. Use extra caution in rocky, complex terrain, near convexities, and on slopes with inconsistent snow depth.

    Persistent slab avalanches that broke in sheltered terrain.

    Photo: Steve Mace

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    Southwest winds continued at strong speeds yesterday. Field observations indicated notable wind transport and continued wind loading near and above treeline. Wind speeds dropped significantly overnight, and we do not expect continued loading today. Recent wind deposits are gaining strength and are likely to be stubborn today.  Exercise caution near ridgelines, in gullies, and on steep leeward slopes. Wind slabs may appear rounded and textured or sound hollow underfoot. Recent avalanches, shooting cracks, and collapsing in drifted snow are warning signs to dial back your slope angle and stick to wind-sheltered areas.

    Smaller avalanches or falling cornices have the potential to step down into buried weak layers, producing even larger avalanches that may propagate widely across slopes and run long distances.

    Photo: Steve Mace

Avalanche Discussion

*Large to very large persistent slab avalanches resulting from the loading event on 2/13-2/14, as well as signs of instability, such as shooting cracks and large collapses, continue to be reported. I highly recommend looking through the recent observations.*

Avalanche conditions vary across our diverse forecast area, and our focus remains on the potential for a large Persistent Slab avalanche breaking 3+ feet below the surface. We are dealing with uncertain and challenging conditions at the moment. As direct signs of instability become less common, it is important to remember that the consequences of an avalanche are incredibly high. Generally speaking, the slab thickness will increase as you move from south to north and as you move up in elevation. Signs of instability, such as shooting cracks and large collapses, will be a more reliable sign of instability in areas with a generally thinner snowpack. However, as the slab gets thicker and these signs become less common, a large avalanche failing in old snow may be the first sign that a slope is unstable.

The key word is patience. We have a long season ahead and it will take time for conditions to become more predictable. In the meantime, conservative terrain choice remains your best tool to ensure a safe and fun day in the backcountry.

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