Lawinenlagebericht

Eastside Region

Eastern Sierra Avalanche Center
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Lawinengefahr

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

Snow showers and increasing winds will create unstable wind drifts today, and will continue to stress the weak layers at the base of our snowpack. These layers are easier to trigger near buried trees, rocks, and shrubs, and in areas with overall shallow snow coverage. Making localized assessments, and sticking to slopes less than 30º without overhead hazards, are your best options to limit your exposure. 

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    2–3.5

    Our weak layers are alive and well, showing numerous signs of instability. We have observed large and very large avalanches in the last 72 hours. Depth hoar and facets remain at the base of our snowpack in areas that had snow in December and January. In areas with shallower coverage overall, it’s easier to trigger an avalanche on these layers. Look for cracking and whumpfing as clear warning signs. In areas with a deeper snowpack, you may not experience any signs of instability. That does not mean the problem is not there. You can still trigger an avalanche on these layers near shallowly buried rocks and trees, convexities, and steep, rocky faces. Persistent slab avalanches can be triggered remotely from above or below, and adjacent to steep terrain. Stick to low-angle slopes with no overhead hazards to limit your exposure.

    (2/5/2024)

    Large persistent slab avalanche off of McGee, observed 02/05 in the am. 

    Photo: Samantha Rubin

  • Wind Slabs

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

    Wind speeds have begun to increase this morning, and will continue to do so throughout the day. There are variable amounts of snow available for transport after the most recent storm, and we are expecting new snowfall today. So, we can expect new unstable wind drifts to form. Old wind slabs from the last three days may still linger. Look for blowing snow and cornice formation as obvious signs of active and recent wind loading. Cracking, textured surffaces, and hollow, stiff-feeling snow are all indicators of the wind slab problem. Even a small wind slab avalanche has the potential to step down into our buried weak layers and trigger a large avalanche involving the full depth of the snowpack. Make localized assessments of leeward terrain features, such as gullies, bowls, and chutes. Sticking to low-angle slopes can help you navigate this problem.

    (1/24/2024)

    A remotely triggered hard wind slab avalanche broke in the recent storm snow and ran on an older wind slab. The crown started 6 inches deep and reached 2 feet deep across the slope. D1.5: about 80 ft wide and ran about 100 vertical feet. Did not step down to buried persistent weak layers.

    Photo: Eastern Sierra Avalanche Center

Avalanche Discussion

Even with minimal visibility, we have observed numerous D2 and D3 Persistent Slab avalanches that have released in the last 72 hours. These avalanches ran at all elevations throughout the forecast region, and indicate our persistent weak layer is still reactive. Field observers reported slope scale collapses in some areas near and below treeline. Other areas seem to display no signs of instability and the depth hoar appears to be broken up by buried ground anchors. Even in areas with a deeper snowpack, our tests have shown that if you find the wrong spot, this layer can still propagate long distances. 

Before the last major storm on February 4th, we were most concerned about near and above treeline terrain because the problem was most reactive at those elevations. We don't have much field data post-storm, but there are some very large crowns in steep, rocky terrain.

As more zones in our forecast region start to have enough snow for "pleasant" travel, and higher elevation terrain becomes more accessible, it is even more essential to be mindful of the snowpack beneath you and the terrain above you.

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