Boletín de aludes

South Columbia

Mar 14 – 15, 2016Avalanche Canada
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Archivado · caducó 11 years ago

Peligro de aludes

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

As stormy weather tapers-off and a dry ridge gradually builds over the province, solar radiation may become the driver for natural avalanche activity.

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–3
    Recently formed wind slabs may remain sensitive to light inputs in higher elevation lee terrain. Brief periods of solar radiation may also promote loose wet avalanche activity on steep, sun-exposed slopes.

  • Cornices

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    2–5
    Large cornices loom over open bowls and alpine faces. Not only are massive cornice falls a hazard in themselves, they can also act as a heavy trigger for slab avalanches on the slope below, especially during periods of solar warming.

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    3–6
    A persistent weakness lies buried up to 110cm below the surface. Although this layer is slowly becoming less likely to trigger, it has the potential to surprise with nasty consequences. I'd continue riding with a conservative mind set.

Confidence

High

Weather Forecast

Light snowfall (2-3cm) is expected on Tuesday and early Wednesday. Clouds are expected to scatter throughout the day on Wednesday, while clear skies are forecast for Thursday. Ridgetop winds are expected to be generally light to moderate and southwesterly on Tuesday, switching to northwesterly by Wednesday. Daytime freezing levels should hover around 1200m for the forecast period.

Avalanche Summary

On Sunday, widespread evidence of natural wind slab activity to size 2 was observed in mostly north-facing alpine terrain. In some cases, wind slabs were triggered by natural cornice falls. The avalanches formed in response to new snow and wind on Saturday night. Persistent slab avalanches continue to fail on the late February weak layer. A sledder was killed on Sunday in a size 2 slab avalanche in the Monashees just north of Shuswap Lake. The avalanche occurred on a west facing convex roll at 1830m. The slab was 40-80cm deep, 60m wide and 65m long. The subject was found after more than an hour of probing as rescuers were not able to obtain a transceiver signal. Although this avalanche occurred only a few kilometers north of the regional boundary in the North Columbia region, similar conditions exist in the South Columbias. This was indicated by another avalanche in the southeast corner of the region (see the Mountain Information Network post near Kokanee Glacier). There a few details regarding the trigger, aspect or elevation; however, the avalanche appears to be at least a size 2 persistent slab.

Snowpack Summary

On Saturday and Saturday night highly variable amounts of new snow fell (10-47cm) throughout the region. Another 5-15cm fell on Sunday night. Moderate to strong ridgetop winds have shifted the snow into wind slabs in leeward terrain at treeline and in the alpine. 60-110cm below the surface you'll find a persistent weak layer comprised of surface hoar, facets and/or a thick crust. This layer, which was buried on February 27th, seems variably reactive. In other words, it's still touchy in some places while in other places it's really tough to trigger, and there's not much of a reliable pattern telling us what exact aspects are most suspect. I'd continue to be suspicious of steep, unsupported features at treeline and in the alpine as this layer has the potential for very large avalanches. Below this interface, the snowpack is generally gaining strength. At ridgetop, cornices are huge and potentially unstable.

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