Bollettino valanghe

Eastside Region

Eastern Sierra Avalanche Center
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Pericolo valanghe

Wed
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
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

It is still possible to trigger a large avalanche on weak layers near the base of our snowpack, especially in areas where the snowpack is shallow. Warm temperatures and direct sunlight may cause small wet loose avalanches here and there. Traveling on lower angle slopes with no overhead hazard can limit your exposure to both avalanche hazards today.  

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1.5–2.5

    We are still concerned with the weak layers at the base of our snowpack. Depth hoar from December and facets from 1/02 remain active beneath a stiff slab of snow.  The depth of these layers and the stiffness of the slab vary, even on the same slope, making this problem very difficult to manage in the backcountry. In some places, these layers are buried a foot beneath the surface of the snow, and may be much easier to trigger. In others, they are buried up to 5 ft deep, and are harder to access. In areas where the snowpack is deeper,  you may not receive any warning signs of this problem - like shooting cracks or collapses - until it is too late. Persistent slabs can be triggered from adjacent slopes, or from above or below. You are most likely to trigger a persistent slab avalanche in an area where the snowpack is thinner overall, or near steep, rocky terrain features. The best way to manage this hazard is to stick to slopes below 30º with no overhead hazard. 

    (1/28/2024)

    Northeast aspect above 11,000 feet on Mt. Olsen, Virginia Lakes.

    Photo: Clancy Nelson

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    1–1.5

    A melt-freeze crust has developed on all aspects at near and below treeline, and on solar aspects above treeline. Despite a refreeze, temperatures will rise quickly today at all elevations. Loose wet avalanches are not impossible in isolated terrain features with today's warm temperatures and direct sunlight. Even small, wet loose avalanches can be dangerous in consequential terrain. Rollerballs, glopping, and sinking deep into wet, mushy snow with your boots are all signs that it may be too wet, and it is time to change aspects or head home. 

    (1/28/2024)

    Natural rollerballs on solar slopes at 10,600 feet around 1 pm in Virginia Lakes.

    Photo: Clancy Nelson

Avalanche Discussion

Today is peak Juneuary, folks! Enjoy it while it lasts! We are looking at incoming weather sometime later tomorrow. 

Distribution and reactivity of the persistent slab problem is continuing to change at varied rates across our forecast region. 

We are seeing the earliest stages of healing in our Dec. depth hoar, and in our 1/02 facet layer, in areas where the snowpack is deeper and the weak layers sit beneath a very stiff slab. These layers are still proving reactive, even in a deeper snowpack, but are becoming harder to trigger. In some lower elevation locations, the Dec. depth hoar has become moist and then refrozen, which has helped it begin to gain strength. However, in other places, it remains dry and is still our primary layer of concern. Variability exists even across the same slope. 

In areas with a thinner snowpack, these layers are much closer to the surface, and even less healing has been observed. We still have many unknowns about how these layers are responding to the warm temperatures above treeline, but various, sizeable persistent slab avalanche crowns have been observed within the last 7 days near and above treeline.

With the formation of a new melt freeze crust at the surface of our snowpack, we may see significant surface instabilities develop as this next storm moves in Wednesday evening. Snow grains just beneath the crust have been observed as both faceting and rounding, and surface hoar has been observed growing at the surface of the crust. We are paying extra attention to both PWLs and to these new surface layers, as these will all be causes for concern under the new load. 

 

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