Boletín de aludes

Central Cascades

Central Oregon Avalanche Center
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Peligro de aludes

Thu
Alta montaña
4 · Fuerte
Límite del bosque
4 · Fuerte
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

On Tuesday avalanche activity was widespread.  Another 12 hours of heavy snowfall means that elevated avalanche danger will continue into Wednesday.  Very large avalanches are possible on wind loaded slopes and slopes where persistent weak layers exist.  This means that travel in avalanche terrain is not reccomended near treeline and in the alpine on north or east slopes.  Below treeline excercise conservative decision making.

Problemas de aludes

  • Wind Slabs

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

    Steady winds from the West will accompany the heavy snowfall overnight.  This will have the dual effect of moving new snow onto east facing slopes, and packing the grains into a consolidated slab.  Extreme winds tend to create unusual loading patterns and we sometimes find Wind Slabs further downslope even in meadows and glades below treeline.  Strong and Moderate winds on Wednseday will create more regular Wind Slab development immediately below ridgetops and behind cross-loaded features.

    The greatest danger is that a Wind Slab avalanche could step down to persistent weak layers in the old snow and lead to a very large avalanche.

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    2–3

    On Tuesday observers ski cut a small Wind Slab only to have a larger avalanche release on a  persistent weak layer beneath last weekend's storm snow (see picture).  The avalanche we triggered failed on 1.5mm facets 45-60 cm. down, but this is not the only persistent weak layer in our snowpack.  Several layers of small facets and burried surface hoar exist in what was last week's upper snowpack (target your obs. to the 30-40 cm. of obviously old snow beneath last weekend's storm snow).  Today, I felt continuous collapsing (whumphing) on low angle terrain, and could easily feel weaker layers by pole probing (pushing my pole gently into the snow, basket or handle first).  As more and more snow piles up, the consequences of triggering avalanches on these layers will increase.

    (1/9/2024)

    Perisistent Slab near treeline, NE slope.

    The crown was 60 cm. at it's tallest.  I'm pointing at the bottom of today's storm snow which was down approx. 40 cm.

    The weak layer was 1.5 mm facets beneath last weekends storm snow.

    Photo: Jonas Tarlen

  • Storm Slabs

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

    On Tuesday I observed small natural Storm Slabs and could easily trigger avalanches on test slopes.  I saw shooting cracks and felt collapses.  The key to obtaining these observations was putting in my own skin track now and again.  Traveling in an existing track gives you very little information as to what's going on with the latest storm snow.  Storm slabs often form when we receive prolonged periods of heavy snowfall.  As we will continue to have very heavy snowfall overnight Storm Slabs will continue to be likely.

    Pay attention to whether or not the surface snow is cohesive.  Hand shears and traveling over small, steep, convex test slopes are my favorite ways of assessing the Storm Slab avalanche problem. 

    (1/9/2024)

    D1 skier trigger, below treeline, N, estimated 38 degrees

    Photo: Gabriel Coler

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