Boletín de aludes

Purcells

Jan 15 – 16, 2015Avalanche Canada
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Archivado · caducó 12 years ago

Peligro de aludes

Sat
Sun
Alta montaña
3 · Notable
Límite del bosque
3 · Notable
Bajo el límite
2 · Moderado
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Lo esencial

Storm conditions will create new problems for the weekend but don't forget about the tricky persistent slab problem.  Large, destructive avalanches remain possible.

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–3
    New snowfall combined with strong SW winds will result in new wind slab formation on Friday.

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    2–5
    The mid-December weak layer remains problematic at and just below treeline where the snowpack structure may still be primed for human triggering in some areas.  The weight of the new snow may increase the reactivity of this layer.

  • Loose Dry

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–2
    The new snow sits on a layer of large surface hoar. Fast sluffing from steep terrain may run farther than normal.

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

The cold front passes over the interior regions on Friday and should be finished by Friday evening. The Purcells region can expect 10-15mm of precipitation with freezing levels of 1200-1400m. Alpine winds are expected to be strong from the SW but may switch to NW at the tail of the storm. On Saturday, light precipitation (1-3mm) is forecast with freezing levels around 800m and moderate SW alpine winds. The next frontal system is expected for Sunday and is forecast to bring another 10-15mm of precipitation.

Avalanche Summary

No new avalanches reported on Wednesday. Explosive control on Tuesday produced two size 2 slab avalanches in the deeper western part of the region. These avalanches released on the mid-Dec layer down 90-100cm on steep north aspect slopes. Some natural avalanche activity is expected on Friday in specific areas including fast sluffing from steep terrain and wind slabs in leeward alpine features.  Small avalanches have the potential to step down and trigger a persistent slab which would greatly increase the consequences. Skier triggering is likely in wind loaded areas and steep terrain, and remains possible for persistent slabs where the tricky mid-December layer is still intact.

Snowpack Summary

The snowfall is burying widespread 10-20mm surface hoar, a sun crust on steep sun exposed slopes, and/or wind affected surfaces in the alpine. The problematic mid-December surface hoar/crust layer is typically down 40-80cm below the new snow and remains sensitive to human triggering is some areas. The reactivity of this persistent weak layer appears to be quite variable but still has the potential for large, destructive avalanches in some areas. The layer appears to be the most reactive at and below treeline.  The mid-Nov weak layer is near the bottom of the snowpack but has generally become inactive.

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