Bollettino valanghe

Eastside Region

Eastern Sierra Avalanche Center
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Pericolo valanghe

Fri
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Snow showers and shifting winds will create unstable wind slabs around the compass rose and will continue to load the weak layers at the base of our snowpack. Triggering a large avalanche with minimal warning is possible in areas where the snowpack is shallower, and near shallowly buried rocks and trees. Avoiding steeper terrain and overhead hazard may help limit your exposure today. 

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Very Likely
    Dimensione
    1–2

    We've observed numerous natural and human triggered wind slabs in the last 24 hours. In addition, as the winds shift around the compass rose with continued snow showers, reactive wind slabs may be found on all aspcets. You may find unstable wind drifts on southerly aspects that are traditionally scoured, and you may witness extensive cross-loading on easterly and westerly slopes. Localized assessment of terrain features such as gullies, chutes, bowls, and slopes just beneath ridgelines can help you understand where this problem exists today. Look for blowing snow and cornice formation as signs of active wind loading. Wind stiffened, textured snow and cracking at the snow surface can clue you in to the problem as well. Keep in mind, even a small wind slab avalanche can run a great distance down the slope, and can even step down to our persistent weak layers. This could trigger a large avalanche involving the entire snowpack. Avoiding steeper slopes and overhead hazard can limit your exposure today. 

    (2/7/2024)

    Skier triggered windslab, June BC

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    2–3.5

    It feels like managing our persistent slab problem may get more difficult before it gets easier. In tracking where our weak layers lie and how reactive they are, we are starting to see increased variability throughout our region. You could trigger a persistent slab avalanche today in areas with a generally shallow snowpack, or in areas with a deeper snowpack via "thin spots," such as shallowly buried rocks, trees, convexities, and steep, rocky faces. Signs of instability, such as shooting cracks and wumpfing, may or may not be present. These avalanches can be triggered remotely, or from above or below. Avoiding overhead hazard, and sticking to slopes less than 30º, can help you manage this problem today. 

    (2/7/2024)

    Shooting cracks as a result of a slope-wide collapse broke down to large facets near the ground. This situation was widespread near treeline on northwest, north, and northeast aspects.

    Photo: Clancy Nelson

Avalanche Discussion

Wind slabs may feel more "in your face" today. However, it is important to remember that in addition to our wind slab instability, we are still dealing with persistent weak layers at the base of our snowpack at all elevations where snow existed before this most recent set of storms. 

In areas throughout our region with a shallower snowpack overall, (areas south of Mammoth and further from the crest in particular), our Dec. depth hoar is buried less than 3 ft beneath the snow surface. It is showing significant signs of instability, as well as variability in where it lies, how deep it is, and whether or not it is broken up by ground anchors. In other areas of our region, such as areas near the crest and in and north of Mammoth, our weak layers are buried more deeply (over 4 ft). They are showing fewer signs of instability, but we are still seeing large persistent slab avalanche crowns, and the depth hoar is still present and well- defined. Some avalanche paths are running or have run multiple times. Some seem to be long overdue. Even in areas where the snowpack is generally deep, shallow spots may exist, especially near steep, rocky slopes or on the edges of avalanche paths, or near convexities. Triggering a deeper persistent slab avalanche would be, almost certainly, unsurvivable. Persistent slab problems can be quick to form and slow to heal. Even in areas with more robust coverage, our weak snowpack has not had enough time to adjust to the continual loading of the past week. Conservative terrain choice is still your best bet for limiting your exposure. 

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