Lawinenlagebericht

Eastside Region

Eastern Sierra Avalanche Center
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Lawinengefahr

Tue
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
3 · Erheblich
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Kernpunkte

While natural avalanche activity is not likely today, the weight of a rider may be all it takes to trigger a large and destructive avalanche. CONSIDERABLE avalanche danger exists at all elevations. Carful snowpack evaluation, deliberate terrain choice, and conservative decision making are essential.

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–2.5

    Extreme SW winds continued to transport snow at all elevations throughout the day yesterday.  Expect resulting wind slabs to be large today and sensitive to human trigger.  While winds are forecasted to drop significantly today and shift to the north the low-density nature of our recent snow may allow for some transport even at lower wind speeds. Be particularly aware if you notice the winds outperforming the forecast.  Be suspect of terrain features that encourage drifting such as the leeward sides of ridgelines, gully features, and cross-loaded depressions. Remember, strong winds can distribute snow in unexpected ways. Don’t be surprised to find wind deposits at lower elevations and further down slopes than you may typically expect to find them.  Blowing snow, recent cornice growth, stiff hollow feeling upside-down snow and a textured, uneven snow surface are all signs of recent wind transport. Use these signs to identify and avoid slopes with recent wind deposits. 

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    2–3

    This weekend's storm added a significant load to our weak and complex snowpack. While this load may have been enough to tip the scales on its own in some areas, in others the snowpack may still be hanging in the balance. The weight of a rider or a relatively small wind slab avalanche might be all that is needed to tip the scales and trigger a large destructive avalanche today.  Persistent Slab problems challenge our patience. Managing this problem requires extensive evaluation and deliberate terrain choice. Don’t be afraid to investigate the lower reaches of the snowpack to see if old snow is present in the areas you wish 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 slab and in some cases persistent slab avalanches can be remotely triggered from adjacent slopes. Give yourself a wide safety margin, be wary of hazard that may reside above you, and use terrain choice to limit your exposure.

Avalanche Discussion

As the skies clear and we move into a period of quiet weather, don’t let your powder fever lure you into making poor decisions. More avalanche related fatalities occur during periods of CONSIDERABLE hazard than any other. Human triggered avalanches remain likely today and resulting avalanches have the potential to be very large and destructive. Our forecast area provides a unique challenge to the backcountry enthusiast. The sheer size and diversity of our terrain often means a dramatically different snowpack from one end to the other. This latest storm is a great example of this. While the Mammoth area received the highest snow totals (30+” of snow and ~3.5”~of water equivalent) areas to the north and south of Mammoth received significantly less. There are also likely to be places near the crest or at higher elevations that received even more snow. This wide range of snow totals has a large impact on local hazards and travel implications. Take our persistent slab problem for instance. Counterintuitively, areas with a more shallow coverage, may show a more reactive snowpack providing backcountry travelers with clear warning signs (whumpfing sounds, collapsing, shooting cracks). Conversely, in areas that received the high end of the snow totals, these lower weak layers may be more difficult for a skier to impact. However, it is important to remember that this weak underlying base has been confirmed throughout the forecast area. A persistent slab avalanche triggered today is likely to run near the ground and has the potential to be very large and destructive.

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