Lawinenlagebericht

Eastside Region

Eastern Sierra Avalanche Center
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Lawinengefahr

Sat
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Veraltet — dieser Lagebericht ist 3 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Give yourself a wide margin for error to avoid triggering deadly avalanches breaking on old, sugary snow. Very large avalanches have started well below ridgelines and have been triggered remotely. Wind slab avalanches are still possible in steep, leeward terrain. Choose planar slopes less than 30 degrees to avoid the hazard. 

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    2.5–3.5

    We are in a dangerous period with high levels of uncertainty. Looking around at the mountains you can see huge crowns where recent snowfall and wind have overwhelmed buried weak layers. In other areas with similar aspects and snowpack structure, things may be hanging in the balance. Large, sugary facets are buried under stiff slabs that vary in thickness depending on where the most recent storm snow fell. The weight of a rider near a shallow trigger point could result in a destructive avalanche. Persistent slab avalanches often propagate across terrain features and can be triggered from a distance.  Snowpack tests and obvious feedback like cracking or whumpfing may not alert you to the hazard lurking below the surface. The best management strategy is to put a wide margin between yourself and the terrain where the problem may exist. When in doubt avoid being on or underneath slopes greater than 30°.

    (3/2/2023)

    Very large persistent slab avalanche in the Bishop area

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1.5–2.5

    Strong and shifting winds over the past 72 hours have distributed dense, rounded slabs across multiple aspects. Increasing southwest winds overnight may continue blowing snow onto northeasterly slopes throughout this morning. Expect the largest and most concerning deposits below ridgelines and in cross-loaded gullies near and above treeline. Hollow, drum-like snow that cracks around you means you’ve found the problem. Sheltered terrain and low slope angles are the best strategies to avoid triggering large wind slabs in steep and consequential terrain. 

    (2/28/2023)

    Large wind slab avalanches in Bishop Creek

  • Loose Wet

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

    Strong solar radiation will warm the surface again today. With limited wet loose activity from yesterday’s warm-up, it’s possible that lower elevations may thaw again. Watch for rollerballs and small sluffs on sunny slopes as the first sign that wet loose avalanches are becoming possible. Rocky chutes, vegetated slopes, and areas with shallow snow cover will be the most concerning. Plan your day to be off of and out from under very steep sunny slopes if the surface crust melts causing you to sink into deep wet snow. 

    (3/2/2023)

    Rollerballs are and early sign that wet snow is becoming unstable. These tumbled down an east-facing slope in Rock Creek on 3/2.

Avalanche Discussion

Reports poured in from across the forecast region yesterday highlighting large and destructive avalanches. Persistent slab avalanches large enough to destroy a house - and then some - likely ran as recently as Tuesday or Wednesday at the tail end of the storm. These failed on well-advertised faceted layers. These layers are buried under the storm snow from the past 10 days, meaning that they may not give clear feedback until they propagate across the slope resulting in unexpectedly large and destructive slides. This problem will not stabilize as fast as storm and wind instabilities. Patience and disciplined terrain choice are key. Usual "safe routes" should be carefully re-evaluated for exposure to overhead hazards.

Wind slab avalanches large enough to bury you ran naturally over the past two days. They have primarily been on slopes drifted over by southwest winds. However, extreme northerly winds two days ago distributed slabs across atypical aspects as well. Be on the lookout for hollow drifts if you venture onto steep exposed terrain features that encourage drifting.

The sun is high in the sky and solar radiation thawed slopes as high as 10,000 feet yesterday. Rollerballs and small wet loose avalanches were the results. Those aspects have crusted over after a good refreeze overnight. Another round of warming will affect steep, rocky terrain at lower elevations today. You can move to shady slopes if you sink deeply into areas with wet snow.

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