Boletín de aludes

Sea To Sky

Feb 15 – 16, 2023Avalanche Canada
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Archivado · caducó 4 years ago

Peligro de aludes

Fri
Sat
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
1 · Débil
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Lo esencial

Avalanches are possible in wind-loaded areas at treeline and above. Winds have changed directions and built wind slabs on all aspects. Carefully evaluate wind loading as you move through terrain and investigate the bond of wind slabs to the crust below them before committing to a slope.

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–2.5

    Strong northerly winds are redistributing 20 cm of storm snow into lees on south slopes. Watch for areas that have been reverse-loaded and cross-loaded.

    On Wednesday winds change to southwesterly and will begin building fresh wind slabs on north and east slopes. Look for fresh windslab development as you travel to higher elevations.

    During periods of direct sun watch for slab properties increasing in surface snow. Minimize exposure to steep sun-exposed slopes, especially when solar radiation is strong.

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Unlikely - Possible
    Tamaño
    1.5–3

    Two weak layers consisting of a crust with small facets found above them have been reactive to rider traffic in the last week. The first, down 40-100 cm has been reactive at treeline in the Rhododendron and Pemberton Icefields area. The second is found up to 1900 meters and is down 60-150 cm in the snowpack. It has been reactive to human triggering in the Brandywine region. Both of these layers seem like isolated problems at the moment but if triggered they will result in large consequential avalanches.

Confidence

Moderate

Avalanche Summary

On Monday afternoon, search and rescue technicians responded to a fatal avalanche incident north of the Sea to Sky region. The avalanche is believed to have occurred on Saturday and was initiated in a shallow rocky area. See the MIN for more details.

On Saturday, wind-affected snow was reported to be reactive to skier traffic. A size 2 wind slab avalanche was skier triggered on a west aspect at 1700 m as the skier passed over a convex roll. See MIN for photos of the slide. A skier accidental size 1.5 storm slab avalanche was reported on a steep, northeast, treeline feature.

Evidence of several size 3 natural slab avalanches was observed. It is believed these avalanches ran within the storm on the late January persistent weak layer.

On Wednesday, a rider triggered a size 2.5 persistent slab avalanche on a weak layer from mid-January. See MIN for photos and details.

Snowpack Summary

20-70 cm of storm snow from the week has been redistributed by variable winds into wind slabs on all aspects at higher elevations. As you descend in elevation wind effect decreases and the temperature effect increases and the new snow may overlie a crust.

A series of crusts are found in the mid-pack at varying depths throughout the region. A crust from late January is found at all elevations down 40-100 cm with small facets above it. In the Rhododendron and Pemberton Icefield area, this crust has been reactive to skier traffic and in test pits at treeline. In the Brandywine area, a crust found 60-150 cm deep resulted in a few surprisingly large rider-triggered avalanches last week. This layer exists to 1900 m in these areas.

Total snowpack depths are reaching 300 cm in some areas.

Weather Summary

Tuesday Night

Clear skies. Light northwest winds switch to the west. Treeline temperature -9 °C. Freezing levels drop to valley bottom.

Wednesday

Mainly sunny with clouds increasing in the afternoon. Winds southwest 10 to 25 km/h. Treeline temperature -7 °C. Freezing level 600 m.

Thursday

Mainly cloudy with isolated flurries, 2-3 cm accumulation. Winds southwest 20 km/h gusting to 40 km/h. Treeline temperature -9 °C. Freezing level 800 m.

Overnight flurries bring 5-10 cm accumulation.

Friday

Cloudy with isolated flurries, 1-3 cm accumulation. Winds west switching to northwest 20 km/h. Treeline temperature -8 °C. Freezing level 800 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Approach lee and cross-loaded slopes with caution.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.

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