Boletín de aludes

Eastside Region

Eastern Sierra Avalanche Center
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Peligro de aludes

Wed
Alta montaña
2 · Moderado
Límite del bosque
3 · Notable
Bajo el límite
3 · Notable
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Desactualizado: este boletín caducó 3 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Warming snow will continue to be the main conern today. With a poor refreeze at lower elevations and increasing clouds, thaw instability may be more prevalent on northerly aspects than in previous days. Get an early start, and beware of overhead hazards including cornices and pockets of unconsolidated snow. 

Problemas de aludes

  • Loose Wet

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–2.5

    The past two days of warm sunny weather have seen widespread wet loose avalanche activity. These avalanches have been reported on most aspects and at all elevations. Today there are changes in the weather pattern that may affect the likelihood and distribution of wet loose avalanches. Strong ridgetop winds and increasing clouds may limit warming of surface snow on solar aspects and at upper elevations. However, a poor refreeze below treeline last night and the insulating effect of cloud cover may exaccerbate wet snow instability at mid and lower elevations and extend its reach to more northerly aspects. Snow near rock outcroppings, cliff bands, and tight rocky couloirs may warm faster than on less featured slopes with deep and consistent snow cover. Wet snow, rollerballs and pinwheels, and increasing boot penetration are all signs of surface warming that indicate conditions are approaching the threshold for wet snow avalanching. It is good practice to avoid passing underneath steep sun-baked slopes, especially in confined or cliffy terrain that limits options to escape runouts and could concentrate debris flows.

  • Cornices

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–2

    Cracks have begun to show at the roots of large cornices throughout the forecast area. Forecasters witnessed cornice fall avalanches bleow treeline in the Mammoth area yesterday. While cornice fall is most likely along ridgelines near and above treeline, cornices overhang leeward slpoes at all elevations. Cornices can fail without warning and they often break much further back from the edge than expected. Give yourself a wide berth if traveling along a ridge near cornice features, and be wary of traveling on slopes underneath large cornice features.

    Witnessed cornice fall above the entrance to "Hole in the wall" in the Mammoth backcountry. 4/10/23

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Unlikely
    Tamaño
    1–2

    Cold clear nights during short windows between storms at the end of March created thin melt-freeze crusts and weak layers of near-surface facets at various depths within the upper snowpack. Avalanches involving these layers are becoming unlikely. There have been no signs of slab instability, or reported slab avalanches, within the forecast area for over a week. However, it might be worth keeping this problem in mind in areas where surface snow is becoming saturated with melt-water for the first time, or in areas where larger natural triggers exist. Wet loose avalanches, or cornice fall are the most likely triggers for stubborn persistent weak layers today. 

    (3/30/2023)

    Large remotely-triggered avalanche 3/30/23

Avalanche Discussion

Forecasted weather factors such as wind speed, wind direction, and cloud cover have a strong influence over wet snow avalanche hazard. The best way to mitigate uncertainty in the forecast is to keep track of weather as you move in the mountains. For example: If there is no wind in your area then avalanche hazard may be increasing more quickly than in might be in another drainage where strong winds are cooling the snow surface. This applies equally to air temperature and cloud cover. 

Yesterday a wet slab avalanche was reported below treeline south of the forecast area. Without a solid refreeze yesterday, water percolating through the snowpack may make it possible to see slab avalanches breaking on older layers and buried cursts. This potential problem ties into the persistent slab problem and is most likely where melting snow and the persistent weak layers overlap.

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