Boletín de aludes

Sea To Sky

Nov 19 – 20, 2011Avalanche Canada
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Archivado · caducó 15 years ago

Peligro de aludes

Mon
Tue
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
1 · Débil
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Lo esencial

This bulletin is based on limited data. Local variation in conditions and danger levels are likely to exist. To produce more accurate forecasts, we need information. Please send an email to [email protected].

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–3
    Near ridgecrests and terrain breaks, and in cross-loaded gullies.

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–4
    Between 1800-2050m there is a rain crust that provides a consistent sliding layer.

Confidence

Poor - Due to limited field observations

Weather Forecast

Sunday: Expect clouds to build and winds to shift to southwesterly and remain light. Treeline temperatures could reach -5. Chance of flurries late in the day. Monday & Tuesday: Increasing snowfall amounts (up to 50cm) with winds building to strong southwesterlies. The freezing level may climb to 1500m on Tuesday.

Avalanche Summary

Avalanche activity has slowed down with the colder temperatures, but recent reports include wind slab avalanches up to Size 2.5 failing on the crust/surface hoar combo that was buried November 9. Some slabs were up to a metre deep and pulled back into low angled terrain on ridges showing incredible propensity for propagation. The critical elevation band for the crust/surface hoar combo is between 1800 and 2050m.

Snowpack Summary

There has been limited new snow in the past couple of days and the colder temperatures have tightened up the storm snow instabilities. The snowpack sits at about 100cm in sheltered locations at treeline, with deeper, wind deposited pockets in the alpine and around ridgeline features. A rain crust, buried November 9 is prominent between 1800m and 2050m and has surface hoar crystals either above, within or slightly below it. This crust/surface hoar combo is buried 40 to 70cm and is the deeper layer of concern.Another 20-30cm of upside-down storm snow brings total snowpack depths up to a metre or so in sheltered treeline areas, but expect to find much deeper pockets of wind-blown snow immediately down-wind of terrain features and ridge crests. A thick rain crust from last week is 70 or 80 cm off the ground at treeline and lower alpine elevations, with facets above and below in some locations. Above that is a buried layer of surface hoar that formed during the clear weather over the weekend. These weaknesses now have a sufficiently thick and cohesive slab to produce avalanches in most areas and they have all the characteristics of an avalanche problem that could persist for extended periods.

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