Boletín de aludes

North Columbia

Nov 24 – 25, 2019Avalanche Canada
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Archivado · caducó 7 years ago

Peligro de aludes

Tue
Wed
Alta montaña
3 · Notable
Límite del bosque
3 · Notable
Bajo el límite
2 · Moderado
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Lo esencial

30+ cm of new snow is expected by Sunday morning, which will likely result in two things:

1. A touchy storm slab problem

2. Potentially wake up the persistent slab problem

Choose simple terrain on Sunday as the snowpack adjusts to the load of new snow.

Problemas de aludes

  • Persistent Slabs

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

    The rapid load of new snow will be a good test for a buried crust found 60 to 100 cm below the surface of the snowpack. This weekend's storm could potentially wake up this persistent weak layer, and avalanches failing on this interface could be surprisingly large. Given the uncertainty with its likelihood and the severity of its consequences, this persistent slab problem warrants conservative terrain choices.

  • Storm Slabs

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

    Storm totals could exceed 30 cm with a fair amount of wind by Sunday morning. This new layer is unlikely to bond well to the underlying old snow surface and could be easy to trigger. If enough snow accumulates, this problem could be suspect below tree line, especially in the higher reaches of the elevation band where the interface consists of surface hoar on a crust.

Avalanche Summary

Very little avalanche activity has been reported since Tuesday, but anticipate another avalanche cycle this weekend. As storm snow accumulates, human-triggered avalanche activity is likely. 

If you see anything while out in the field, please consider sharing that information with us and the backcountry community via the Mountain Information Network (MIN). 

Confidence

Low - Uncertainty is due to the complexity of the snowpack’s structure. Uncertainty is due to how the snowpack will react to the forecast weather. Uncertainty is due to the limited number of field observations.

Weather Forecast

Saturday night: Another 10-20 cm of snow above 1400 m with moderate to strong southwest winds. 

Sunday: Broken cloud cover, moderate winds shifting to the west/northwest, freezing level around 1000 m and dropping, continued flurries with 3-8 cm of additional accumulation possible.

Monday: Clearing skies, freezing level near valley bottom, light northwest winds, no significant precipitation expected.

Tuesday: Clear, calm, cold, dry.

Snowpack Summary

Winter ramps up this weekend as the latest storm brings fresh snow, heightened avalanche hazard, and a good test for our snowpack. 

Snow totals of around 30 cm should accumulate by Sunday morning with winds primed for snow transport. The new snow is unlikely to bond well with the previously wind-affected surfaces in the alpine and with the crusts/surface hoar that developed near and below tree line. This rapid load may also trigger deeper weak layers formed in mid-November and late October that are now down 60-100 cm.

This storm brings winter lower into the valleys, as snowline could drop to 1000 m. Current total snowpack depths range from about 70 cm below treeline to as high as 200 cm in the alpine. 

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