Boletín de aludes

Northwest Inland

Dec 29 – 30, 2011Avalanche Canada
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Archivado · caducó 15 years ago

Peligro de aludes

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

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Very Likely
    Tamaño
    1–5
    Wind slabs have developed on lee and cross-loaded terrain in the alpine and at treeline.
  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible - Likely
    Tamaño
    1–5
    Persistent slabs have now formed at all elevations where the mid December buried surface hoar/crust/facet layers exist. Loading by new snow and wind could be enough to wake these layers up.
  • Storm Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely - Very Likely
    Tamaño
    1–4
    Increasing in size and likelihood with each successive weather system.

Confidence

Poor - Due to limited field observations

Weather Forecast

A frontal system moves across the region Thursday night extending through mid day Friday bringing light to moderate precipitation and freezing levels near the surface. Winds will be building out of the west, expect values from 50 - 70 km/h in the alpine for the second half of the day. Temperatures will be near seasonal norms with a high of -6 and an overnight low of -12.

Avalanche Summary

Observations from the Microwave area (S. of Dennis Lake) on Dec. 26: Several easily triggered soft slabs on steep features up to treeline. No alpine observations due to cranking winds and blowing snow. I would expect some natural avalanche activity at higher elevations, primarily in wind loaded terrain.

Snowpack Summary

Strong winds have been the biggest story recently. Exposed windward slopes have been scoured and wind slabs have formed in lee terrain and may be susceptible to human triggering. There is now around 55-70cms of snow sitting on a surface hoar/crust/facet combo which is the result of the early December dry spell. This crust is widespread and exists in most start zones up to 2000m. Facets can reportedly be found above or below the crust. Prior to being buried, the surface hoar was destroyed by high winds in the alpine, but still coexists with the crust at treeline and below. What is the tipping point of this weak interface? In areas where this interface has reached its threshold, natural and human triggered avalanches up to size 2.5 have occurred. If they have yet to happen, I suspect they are gaining some strength but would still react to a rider trigger, especially in steeper, unsupported terrain features. In short, the upper snowpack is variable and deserves caution. It will also see increased load with forecast wind and snow. Beneath this the midpack is well settled and strong.

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