Boletín de aludes

West Slopes North

Northwest Avalanche Center
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Peligro de aludes

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

Lo esencial

Sun and warm temperatures will keep wet avalanches concerns on the southerly half of the compass elevated. Avoid traveling on or under steep slopes where you find wet, heavy snow, or see signs of instability like rollerballs or fresh avalanches. Avalanches may still occur in wind-drifted pockets of snow on shady aspects at upper elevations. 

Problemas de aludes

  • Loose Wet

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

    A second day of intense sunlight means you can expect to find wet snow with the possibility of avalanches on steep slopes that are directly facing the sun. At first, snow surfaces that previously were wet will be crusty, but they'll likely soften as the day progresses into early afternoon.

    If you start sinking into wet snow more than a couple inches, or if you see precursors to avalanches such as rollerballs, avoid nearby steep slopes and the terrain beneath them.  Shifting to shadier aspects, or maybe even just transitioning from one side of a subtle ridge to the other might mean the difference between finding wet, heavy snow that could slide versus snow that has not been affected by the warming.

    Despite the weak December sun, it has enough impact on southerly aspects to create at least some wet avalanche activity. Continued avalanche activity into Monday may vary greatly depending on where you are in the zone. However, we don't expect as much activity as springtime cycles where the sun is much more intense and wetting impacts further into the snowpack. 

    Example photo: Small wet loose avalanches and rollerballs were easy to spot on sunny slopes as the sun went to work on the new snow.  Photo from Lake Ann area. 

    Photo: Robert Hahn

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–1.5

    An intense period of unsettled weather with many natural and human triggered avalanches ended a week ago, but a slow and steady trickle of wind slab avalanche observations continue to come in. On Saturday a small wind slab was triggered high on the north side of Table Mountain in the Baker backcountry, and an avalanche possibly triggered by cornice fall was observed on Ptarmigan Ridge. Two human-triggered slab avalanches were reported on Friday.

    These all released at or just below ridgeline on slopes with signs of recent wind loading. Track changes in snow depth and stiffness as you gain elevation or change aspects. Don’t forget to look for typical signs of wind loading like cornices and scoured or rippled snow surfaces. Find small, wind-loaded slopes or features to test wind slab reactivity before you jump into high consequence terrain. Getting caught in an avalanche would be most concerning in terrain where you might get buried deep in a gully or dragged over rocks, through trees, or over a cliff.  When in doubt, pick lower-angle slopes when traveling in areas where the wind has been at work.

    (11/30/2024) This wind slab avalanche likely failed due to cornice failure on Ptarmigan Ridge. 

Avalanche Discussion

Conditions vary greatly throughout the zone. In some places you might find reactive wind slabs, whereas in others you may not find any of concern. We also have a lot of uncertainty as to the extent of wet loose activity, since slopes have already been impacted in the last day. It's just the beginning of December yet we're seeing a broad range of avalanche activity. None are very alarming at this time, but it's not green light conditions in the backcountry so be sure to evaluate steep slopes before heading out onto them. 

Snow depths are deep for this time of year in the West North zone, with nearly 5 feet sitting on the ground at the Heather Meadows telemetry site at 4200'. In the last couple days we've noted surface hoar and near surface facets forming on and near the surface thanks to our recent high pressure system. We haven't found any weaknesses deeper in the snowpack.

It's still early season and lower elevation obstacles like rocks, trees and creeks still pose a hazard to be aware of. 

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