Boletín de aludes

Central Cascades

Central Oregon Avalanche Center
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Peligro de aludes

Mon
Alta montaña
3 · Notable
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

For Sunday, avalanches will be likely. A new persistent weak layer buried within the snowpack has produced many avalanches recently. Wind drifted snow near and above treeline will continue to build slabs.  Look for clues of unstable snow such as cracking, collapsing, and recent avalanches. Your best bet is to use conservative decision making and stick to slopes under 30 degrees. 

Problemas de aludes

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1.5–2.5

    We have transitioned away from storm slabs and added persistent slabs to our problem list. This avalanche problem is created when a slab forms above a weak layer of snow (facets or surface hoar). Forecasters have continued to find weak snow (2mm facets) buried 25-27" that is sitting on an ice crust with a slab on top. This layer has likely produced significant avalanche activity the past few days from below treeline to the alpine. On Saturday, shooting cracks and collapses were observed near and below treeline on easterly and north aspects.

    Persistent slabs can catch folks off guard, as they tend to fracture further/deeper than expected and can be difficult to manage. Signs of persistent slabs are cracking, collapses, and recent slab avalanches. However, we do not always get this type of warning with persistent slabs due to spatial variability and slab depth. Your best bet is to be conservative with terrain, and stick to slopes lower than 30 degrees. Also avoid any large run out zones (areas where the debris of an avalanche could reach you.)

  • Wind Slabs

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

    We are expected to receive 5-8” of new snow with moderate southwest winds. This will continue to build large wind slabs near and above treeline on northwest, north, northeast, east, and southeast slopes. We could also see wind slab formation at lower elevations where the wind can move the snow freely (i.e. burn zone). Wind slabs could also step down to trigger a larger persistent slab avalanche. 

    Look for signs of slab formation such as wind drifted snow below ridgelines and areas that catch snow. Clues of wind slabs include textured snow surface, hollow sounding snow, pillow-like features, and blowing snow. Also be on the lookout for red flags such as cracking, collapsing, and recent avalanches. Using small and safe test slopes is great to assess for instabilities. Remember that new snow can be deposited 3-5x deeper due to wind.

Avalanche Discussion

In addition to our slab avalanche problem, it is possible we could see a rain/snow mix at our lower elevation zones. As always, be on the look out for any unstable snow, specifically wet loose avalanches. Signs to be aware of are pin wheels and sinking in wet/slushy snow. Although these will likely be small, be cautious in any steep terrain where getting knocked off your feet could have high consequences (i.e cliffs).

On Saturday I toured out to Black Crater. I dug a snow pit at 6,600ft on an east aspect. I found 1-2mm rounding facets down 27” (70cm). While performing an extended column test, this layer did propagate (ECTP#21). While touring, it was snowing lightly throughout the day with limited visibility. 

 

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