Lawinenlagebericht

Eastside Region

Eastern Sierra Avalanche Center
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Lawinengefahr

Sat
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Kernpunkte

Shallow snow coverage and a complex and weak snowpack will make for challenging travel and hazard assessment.  Persistent slab avalanches are the main concern today. Areas with more significant coverage will also be areas with a more cohesive slab and heightened avalanche concerns. Keep in mind that any avalanche involvement today will come with elevated consequences due to the very shallow and rocky nature of our snowpack.

Lawinenprobleme

  • Persistent Slabs

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

    The slow start to our season has left us with a shallow and heavily faceted snowpack. Recent rain at lower elevations and significant snow at higher elevations have added weight to this weak structure. At lower elevations, weak facets and depth hoar may be gaining some strength after getting wet and re-bonding. However, at higher elevations, facets at the base of the snowpack remain dry and reactive. Areas of greatest concern are areas where winds have added weight and cohesion to the overlying slab. Signs of instability, such as recent avalanche activity, shooting cracks, whumphing, and collapsing in the snowpack, are signs that you may have found this poor structure. It may be possible to trigger a persistent slab avalanche from adjacent slopes, and avalanches may propagate long distances beyond terrain features that typically contain direct action avalanches such as storm or wind slabs. Remember that being carried in an avalanche will have elevated consequences due to our snowpack's very shallow and rocky nature. The easiest way to avoid this problem is to stick to lower-angle terrain without overhead hazards.

  • Wind Slabs

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

    Concerning wind deposits are likely on the mend following several days of mostly light winds and minimal snow accumulation. Lingering wind slabs may still be reactive to human triggers on leeward terrain features near and above treeline.  However, there is relatively high uncertainty around the size, distribution, and reactivity of wind slabs in the high alpine. Identify terrain features that are conducive to capturing wind-transported snow. Surface clues such as stiff and hollow feeling surface snow and large drifts can clue you into areas that may have seen recent loading. Leeward sides of ridgelines, cliff bands, and cross-loaded gully features all deserve evaluation. It’s worth considering that this problem has significant overlap with our persistent slab concern. Even a relatively small wind slab avalanche could step down to deeper layers near the base of the snowpack, creating a much larger and more destructive avalanche.

    (1/6/2023) Photo: Cracking in wind slabs

Avalanche Discussion

It has been a slow start to the winter season here on the eastside. On a regional scale, continuous snow coverage is largely specific to upper elevations and areas closer to the Sierra crest. The exception may be the Mammoth area, where shallow coverage exists below treeline. Regardless of where you decide to travel, you should expect to find a very thin and weak snowpack. Field observations have noted a complex snow structure with very weak and well-developed facet layers near the ground. This has several consequences. Top among them are the avalanche concerns. However, it also means that the snowpack may not be very supportable. If you decide to venture out into the backcountry, be ready to contend with terrain riddled with rocks, fallen trees, exposed bushes, and open water. This will be particularly true at lower elevations. The early season inherently comes with higher levels of uncertainty due to the difficult travel conditions and limited field observations.  As we wait for more snow, slowing down and taking stock of the big picture will be important.   We have a long season ahead, don’t let the lure of fresh tracks end your season before it really begins.

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