Boletín de aludes

Salt River and Wyoming Ranges

Bridger-Teton Avalanche Center
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Peligro de aludes

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

Lo esencial

Backcountry riders and skiers have the potential to trigger slab avalanches today at the  mid and upper elevations in steep terrain. These slabs are not likely to fail naturally but could be triggered if a weak spot in the snowpack is impacted. Rising temperatures will increase the sensitivity of these slabs and provide the chance for small wet loose activity on steep sunlit slopes. Do not interpret the lowering of the danger rating as a green light to all terrain. The threat of human triggered avalanches is real and steep terrain on northerly aspects should be avoided. Snow depths at low elevations remain shallow.

Problemas de aludes

  • Persistent Slabs

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

    Weak snow that formed during a dry period in November remains a concern on west thru north thru east aspects above 8000'.  Cohesive slabs lie over this weak snow. Time and above average temperatures have slowly decreased the sensitivity of these slabs which makes their failure harder to predict. Slabs may still release when the first person impacts the terrain or even after it has been tracked several times when a weak spot on the slope is impacted.  If triggered, these slabs are likely to be hard with crown depths of 1-3 feet. Avoid being in or under steep terrain on these aspects, especially during the afternoon as temperatures reach the upper thirties.

    (12/14/2023)

    This photo identifies the November drought layer. These weak layers can often be visible as a darker color and distinguishable as softer and less cohesive than the snow above.

    Photo: Alex Drinkard

Avalanche Discussion

When there is a persistent weak layer (PWL) involved, a decrease in the danger rating from  Considerable to Moderate rating shows that the likelihood of triggering a slab has decreased, but that can also be stated that slabs have become more “stubborn”. The moderate rating still means human triggered slides are possible, especially in steep terrain where the old weak snow lies. These "stubborn" conditions demand respect as large avalanches can still occur, even after a slope has been tracked many times. When persistent slab problems evolve to this stage, vigilence and  careful terrain evaluation is important. 

There is a lot of snowpack information currently available for all three forecast areas. Reading the posted observations shows that the PWL (persistent weak layer) has a lot of variability with some areas having simply a thick faceted snow layer and others having a mix of facets (including surface-hoar), melt-freeze, and rain-crusts. All of these fall into the PWL classification. Many observations describe concerns with the current strength of the snowpack and note wise decisions to stay on powdery, lower angle terrain. 

The current dry period is providing for future concerns with south facing slopes forming melt-freeze crusts while surface facets and surface hoar form in colder shaded terrain.  Take a look at the snow layering for a better understanding of stability now and to make informed future decisions when precipitation returns to the area.

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