Lawinenlagebericht

Eastside Region

Eastern Sierra Avalanche Center
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Lawinengefahr

Sat
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
2 · Mässig
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Kernpunkte

Dangerous avalanche conditions exist. Our weak snowpack just received the most significant stress of the season. While natural activity has become less likely, human-triggered avalanches remain likely. Avalanches failing in the new snow could be large and avalanches failing at the base of the snowpack have the potential to be very large and potentially deadly.

Lawinenprobleme

  • Storm Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    Field observations yesterday suggest that our new storm snow is consolidating relatively quickly but not bonding well to melt freeze crusts at the new/old interface.  Storm slabs will be more stubborn today, but if initiated, an avalanche breaking in the new snow could be sizable, involving all of the new storm snow.  Approach steep slopes with caution and be mindful of your exposure to terrain features that increase the consequences of avalanches. This includes road cuts, gully features, cliff bands, and mid-slope depressions.

    Photo: Steve Mace

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–2

    Winds are expected to drop today but remain out of the southwest at transportable speeds.  Expect continued slab development on leeward terrain features near and above treeline, particularly if snow totals outperform the forecast. Be suspect of terrain features that encourage drifting such as the leeward sides of ridgelines, gully features, and cross-loaded depressions. Surface clues such as recent cornice development, drifting, and hollow drum-like snow are all signs that can indicate areas with recent wind deposits. Keep in mind that even relatively small avalanches breaking in the upper snowpack have the potential to step down into older snow, creating a much larger and more destructive avalanche.  

    (12/28/2022)

    Size 2 human-triggered wind slab in Redcone Bowl

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1.5–3

    As this most recent storm moves out of the area, it's important to keep in mind that a significant load (2+ ft of new snow and over 2” of water weight) has been added to our weak snowpack over the last 48 hrs. While this loading event may have been enough to tip the scales in some areas, in others, the snowpack may be hanging in the balance and waiting on a trigger. This is particularly true near and above the treeline, where basal facets remain dry and well-formed following our latest warm-up. If triggered, the resulting avalanche could break with little warning, involving the full depth of the snowpack. It may be possible to trigger a persistent slab avalanche from adjacent slopes today. Avalanches may propagate long distances and beyond terrain features typically containing surface instabilities such as storm or wind slabs. As this weak layer gets buried deeper, signs of instability, such as shooting cracks and collapsing, may become less prevalent. This means that avalanches may fail with little or no warning signs. Cautious route selection remains the most effective strategy to manage this problem.

    Very Large Persistent Slab Avalanche - Wall of the future - McGee Drainage

    Photo: Steve Mace

Avalanche Discussion

Don’t let powder fever lure you into making poor decisions today. While storm impacts have diminished, and natural activity has become less likely today, it remains likely for backcountry enthusiasts to trigger potentially deadly avalanches. We are entering a dangerous period. Signs of instability are becoming less obvious, but avalanches involving the full depth of the snowpack remain likely. Uncertainty exists with how our weak snowpack will adjust to this new load.  What is more certain is that our snowpack just received the largest stress of the season and we can expect large avalanche activity as a result. 

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