Bollettino valanghe

Eastside Region

Eastern Sierra Avalanche Center
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Pericolo valanghe

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

MODERATE avalanche danger exists at all elevations today. Evaluate snow and terrain carefully and use terrain choice to mitigate your exposure to large and destructive persistent slab avalanches. Wind slabs of varying size and sensitivity will also be possible to find near and above treeline.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3

    Our Persistent slab problem is entering a frightening phase where avalanches are becoming more difficult to trigger, predict, and manage while continuing to show the size potential to destroy a large truck or small house; and certainly large enough to bury or kill a person.  Persistent Slab problems challenge our patience. Managing this problem requires extensive evaluation and deliberate terrain choice.  Don’t be afraid to dig in and get a look at the lower layers of the snowpack to see if old snow is present in the areas you want to travel. Remember that persistent slab avalanches often propagate across and beyond terrain features that would otherwise confine surface instabilities such as wind or storm slabs. In some cases persistent slab avalanches can be remotely triggered from adjacent slopes. Give yourself a wide safety margin, be wary of hazards that may reside above you, and use terrain choice to limit your exposure.

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2.5

     Wind slabs will vary in size and sensitivity today, and may be present on all aspects near and above treeline. Wind slabs deposited during, and immediately following our last storm have gained strength over the last 24 hours. However, they have the potential to be quite large and may still be reactive to human triggers. In addition, winds have shifted around the compass rose and risen to moderate speeds. While relatively small, fresh wind slabs may have developed on more southerly aspects in the early hours this morning.  

    Exposed areas and leeward catchment zones near and above treeline deserve elevated caution. Large drifts, recent cornice growth, and uneven snow surfaces are all clues that indicate nearby wind deposits. Do your own localized assessments and be suspicious of terrain features that encourage drifting such as the leeward sides of ridgelines, gully features, and cross-loaded depressions.

Avalanche Discussion

You have probably heard the term “Spooky Moderate”. That was a phrase commonly used last night as the forecast team met to discuss our current Persistent slab problem. We continue to get reports of large collapses, shooting cracks, and propagating test results which are all signs that point to the ability of a skier to initiate a failure, and for avalanches to propagate across the landscape. However, the last reported avalanche occurred within our forecast area on December 4th and while the persistent weak layer is widespread, the persistent slab problem seems to be more specific in nature. It is important to note that we as a forecast team have high uncertainty around the distribution and sensitivity of this problem in the high alpine as well as on the extremes of the compass rose (W & SE).  It will be imperative to keep this problem at the top of your mind if you decide to head into the backcountry today. We are dealing with a challenging and complex snowpack and it is still possible for a skier or rider to trigger a large and destructive avalanche.  Patience is KEY right now, allowing powder fever to get the best of you could be a costly mistake. When uncertainty is high, it is best to give yourself wide margins for error and to stick to more simple terrain.

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