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

Human triggered avalanches will be likely on Sunday.  Large slabs and loose avalanches will be present on all elevations and aspects. Be conservative in steep and committing terrain and if in doubt stick to terrain below 30 degrees. 

Problemas de aludes

  • Wind Slabs

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

    On Saturday I triggered several small (D1) wind slabs near treeline on north and northeasterly aspects. For Sunday we can expect small to large human triggered wind slabs likely. With more snow in the forecast and sustained moderate west wind, slabs will continue to build on northerly, easterly and southerly aspects. 

    Wind slabs often form below ridgelines and areas that catch blowing snow. These slabs can also form in lower elevation areas such as burns or anywhere the wind can move snow. Be on the lookout for pillow-like snow features, rounded domes, and wind rippled snow surfaces. Assess for slab formation as you travel, and use small/safe test slopes to look for signs of instability. If you encounter cracking and/or see avalanches, seek lower angle terrain. 

  • Storm Slabs

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

    With significant new snow and more snow in the forecast (8-14" possible), storm slabs will be likely.  Be cautious, especially in steep and unsupported terrain. Use tests such as hand shears to assess for cohesion and safe test slopes to look for signs of instabilities. If in doubt, stick to lower angle terrain.

  • Loose Dry

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

    Dry loose avalanches were easily triggered on Saturday. With deep and unconsolidated snow, dry loose avalanches will be likely in steep terrain. Overall, I expect these to be small; however, larger avalanches will be likely in bigger terrain. Be cautious on committing slopes and areas with terrain traps below (i.e trees, cliffs, gulleys, tree wells). 

    Dry loose avalanches start below you feet or sled and entrain surface snow as the avalanche descends the slope. If in this type of terrain, you can ride out of the fall line to help manage the sluff.

Avalanche Discussion

Saturday at Tam Rim graupel fell from the sky for a short period of time in the afternoon. Graupel is snow crystal that becomes covered by rime and forms in a ball shape. If buried, graupel can act as a weak later. As this layer gets buried deeper from new snow and a slab forms on top, be cautious as this can cause slab avalanches to be easier to trigger and propogate larger. I do not believe the graupel fell area wide, however it might be worth digging into the snow to assess for this layer. The graupel layer likely accumulated more on lee aspects (northerly and easterly slopes).

We have also been finding some patchy surface hoar on northerly aspects near and below treeline. On Saturday I found surface hoar 65cm deep (7,390ft on NE aspect) and there is possibly another layer over a meter deep in other locations. I did not see any natural or human triggered avalanches on these layers, however I would carefully evaluate the snowpack on northely aspects and use conservative decision making. Persistent slab avalanches can be very large and hard to predict.

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