Bollettino valanghe

Eastside Region

Eastern Sierra Avalanche Center
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Pericolo valanghe

Mon
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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In sintesi

Avalanches will become increasingly likely throughout the day as the snow surface warms. Warming may increase the potential for slab avalanches failing on buried weak layers, and for large cornice features to break loose. Monitor surface melt closely, be aware of overhead hazards, and be ready to retreat as surface snow becomes wet and unconsolidated.

Problemi valanghivi

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2.5

    Clear skies and cooler-than-expected overnight temps led to a moderate refreeze. However, we can expect surface snow to melt quickly as the sun comes out and we reach above-average temperatures today.  Loose wet avalanches will be increasingly likely by midday. Solar aspects have undergone several rounds of melt-freeze at this point and areas of unstable wet snow may be more likely on northerly aspects and at higher elevations where surface snow is still under transition. Areas near rock outcroppings, cliff bands, and tight rocky couloirs where the effects of warming are amplified will also present elevated hazards. Wet, sticky snow surfaces, rollerballs and pinwheels, and increasing boot penetration are all signs of surface warming and may foreshadow larger point-release avalanches. Be wary of overhead hazards today and be ready to retreat if the surface snow thaws causing you to sink into deep wet snow. 

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1.5–3

    Weak faceted snow and melt-freeze crusts exist at various depths in the upper snowpack. Over the last week, we have seen a decrease in signs of instability on these layers, and the last reported avalanche breaking on these layers occurred 7 days ago. However, high levels of uncertainty still exist. Rapid warming could reinvigorate these concerning layers making it easier for a rider to trigger a large slab avalanche. Feedback - like whumpfs, shooting cracks, and collapsing in the snowpack - may be spotty and unreliable. If triggered, persistent slab avalanches can propagate beyond terrain features and they can be triggered from a distance. Large natural triggers, like cornice fall, are something to consider if you travel under slopes with big wind lips overhead. Use terrain choice to limit your exposure and be wary of convex rollovers, wind-loaded terrain features, and areas where the upper snowpack is getting wet and punchy.

    (3/30/2023)

    Remotely-triggered avalanche of Punta Bardini 3/29/23

  • Cornices

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

    Our very productive precipitation cycles this winter have led to some truly impressive cornice features near and above treeline. As we continue to see above-average temperatures this week natural cornice failures are becoming more likely. Given the sheer size of some of these features, falling blocks of dense snow have some serious destructive potential. Predicting the timing and exact size of a cornice failure is nearly impossible. They can fail without warning and they often break much further back from the edge than expected. It's also important to consider that cornice failures can act as large natural triggers for more stubborn weak layers within the old snow. Give yourself a wide berth if traveling along a ridge near cornice features and be wary of traveling on slopes underneath large cornice features.

    (3/31/2023)

    Small natural avalanche in Redcone bowl triggered by direct wind loading. 3/31/23. N, 10,300'.

Avalanche Discussion

Rapid warming continues to be the main driver of instability as we move through this period of above-average temperatures. Freezing temperatures overnight have been beneficial so far but it is important to remember that our snowpack has not yet transitioned to a predictable spring pack. Areas of cold dry snow are still being found at upper elevations and sticky wet snow is making for challenging travel on polar aspects.  Keep in mind that avalanches resulting from warming are difficult to predict and often fail without warning. It is a good idea to give things like glide cracks, large cornice features, and steep slopes near rock outcroppings a wide berth.

In addition to the avalanche concerns today, there are several objective hazards to keep in mind if you decide to head into the backcountry. Hard and slick surfaces can be found at all elevations and aspects and tools like boot and/or ski crampons and an ice ax may be necessary depending on where you wish to travel. Creeks are starting to open in areas and snow bridges may no longer hold your weight. Furthermore, with such good coverage throughout the range, typically overhead powerlines are near or even below the surface of the snow in some areas. Many of these lines are live and it’s recommended that humans stay at least 10’ away from exposed lines.

 

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