Bollettino valanghe

Eastside Region

Eastern Sierra Avalanche Center
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Pericolo valanghe

Tue
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
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In sintesi

It remains likely for humans to trigger large and destructive avalanches at any elevation today. Persistent slabs can fail with little warning and act in surprising ways. You could trigger an avalanche today from a distance or  in areas you may typically think of as “safe.” When in doubt, use terrain choice to limit your exposure by sticking to lower slope angles without overhead hazards.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1.5–3

    Human-triggered persistent slab avalanches have been reported on a daily basis since our last loading event, and weak faceted grains within the old snow continue to show the potential for failure. If triggered, a resulting avalanche could break with little warning, involving the full depth of the snowpack. It will be possible to trigger a persistent slab avalanche from adjacent slopes today.  Avalanches may propagate long distances and beyond terrain features that typically contain surface instabilities such as storm or wind slabs. Managing this problem is made more difficult because shallow and inconsistent snow coverage on a regional scale means that the few areas attractive for riding are generally the same slopes where the avalanche problem exists. Persistent slab problems require persistent patience and extensive evaluation. Cautious route selection remains the most important strategy to manage this problem. When in doubt, choose travel routes with lower slope angles and no overhead hazards to limit your exposure.

  • Wind Slabs

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

    Wind speeds have decreased over the last 12 hrs, and continued slab development is expected to be minimal today.  It may be possible to find wind slabs ranging in size and sensitivity in leeward catchment zones on more shaded aspects. While more concerning deposits are expected near and above treeline, it will not be impossible to find reactive deposits in more sheltered areas and below treeline. Do your own localized assessments and be suspect of terrain features that encourage drifting, such as the leeward sides of ridgelines, alpine couloirs, gully features, and cross-loaded depressions. It is critical to remember that the distribution of wind slabs overlaps with our persistent slab problem. This means that even a relatively small avalanche breaking in the upper snowpack has the potential to step down into older snow, creating a much larger and more destructive avalanche.

Avalanche Discussion

I’ve heard it said before that “Colorado is where you go to study weak snow, and the Sierra is where you go to ski”.  The implication of this statement is that we generally expect to see a more stable and predictable snowpack here. Well, make no mistake - this is not the typical maritime wonderland we are used to here in the Sierra. Persistent weak layers in the old snow continue to show all of the signs of reactivity (large slope scale collapses, long shooting cracks, and propagating test results), and human-triggered avalanches have been reported on a daily basis since our most recent loading event.

Navigating this persistent slab problem is a complex and nuanced endeavor. One that requires cautious route-finding and critical evaluation. Calm weather will reduce the likelihood of natural avalanche activity today. However, it remains likely for humans to trigger large and destructive avalanches at all elevations and in areas you may typically think of as “safe”. When dealing with unpredictable and atypical conditions, the best strategy is to hit the brakes and stick to lower slope angles. Unfortunately, things do not look promising for a “quick change”. In a season that has already challenged our patience with minimal snow and thin coverage, Patience continues to be the key ingredient.  

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