Boletín de aludes

Cariboos

Mar 6 – 7, 2023Avalanche Canada
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Archivado · caducó 4 years ago

Peligro de aludes

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

Don't let good visibility lure you into dangerous terrain. Avoid wind-loaded features at upper elevations and steer well clear of overhead cornices and sun-affected slopes during periods of strong solar radiation. The best and safest riding will be found in sheltered and shaded locations.

Check out the most recent Forecaster Blog for the latest on the deep persistent slab problem.

Problemas de aludes

  • Wind Slabs

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

    Last week's snow fell with moderate to strong southwest winds, which recently switched to the northeast. Wind slabs will exist on a variety of aspects in the alpine and exposed areas at treeline, while sheltered terrain may still produce loose dry avalanches - be prepared to manage your sluff.

    Avoid sun-affected slopes in areas that see clear skies and strong sun. Surface snow may rapidly lose cohesion.

  • Cornices

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    2–3

    Minimize your exposure to cornices, they have grown significantly in recent weeks and can trigger large avalanches on the slopes below. Give them respect and a wide birth when you are travelling under them. Be cautious of solar input.

  • Deep Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Unlikely - Possible
    Tamaño
    2.5–4

    A weak layer of facets exists near the base of the snowpack. The likelihood of human triggering is low given the layer's depth, but large triggers such as smaller avalanches in motion or cornice failures have the potential to produce very large avalanches with wide propagation. Suspect terrain for human triggering includes steep, shallow and rocky terrain.

Confidence

Moderate

Avalanche Summary

On Thursday and Friday, storm and wind slabs were reported to size 2.5 from natural and human triggers. Operators reported rapid loading due to winds at higher elevations but observations have been limited due to visibility and weather. We expect a natural cycle to have occurred primarily in wind loaded features.

On Saturday, two size 1 skier-triggered wind slabs were reported from south-facing alpine terrain. Several natural storm slabs were also reported from south-facing alpine terrain, triggered by strong solar radiation.

The last deep persistent slab avalanches were observed over a week ago, occurring during the very windy arctic outflow event.

Read more about managing the deep persistent slab problem in our latest Forecaster Blog.

Snowpack Summary

Variable winds have redistributed recent storm snow into deeper deposits on many aspects. This storm snow sits over wind effected surfaces and a thin sun crust on steep south facing slopes.

Around 40-90 cm deep a layer of small surface hoar exists in lower elevation sheltered areas. Elsewhere heavily wind effected surfaces exist, with faceted (sugary) snow from the late February Arctic blast. Reports suggest this interface has not yet been reactive.

The remainder of the mid-snowpack is generally strong with a small surface hoar layer from mid February that appears to be spotty and is not producing avalanche activity.

A weak layer of facets that formed in November sits near the base of the snowpack. Although the likelihood of triggering this layer is low at this time, the consequence of doing so remains very high. This layer is most likely to be human-triggered in thin, rocky slopes at alpine and upper treeline elevations.

Weather Summary

Sunday night

Clear periods. Alpine temperatures drop to a low of -12 °C. Ridge wind light from the southeast. Freezing level at valley bottom.

Monday

A mix of sun and cloud with isolated flurries. Alpine temperatures reach a high of -10 °C. Ridge wind light from the south. Freezing level at valley bottom.

Tuesday

A mix of sun and cloud with isolated flurries. Alpine temperatures reach a high of -9 °C. Ridge wind south 15-35 km/h. Freezing level 800 meters.

Wednesday

Sunny with cloudy periods. Alpine temperatures reach a high of -8 °C. Ridge wind southeast 10-30 km/h. Freezing level 800 meters.

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.
  • Minimize exposure to sun-exposed slopes when the solar radiation is strong.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.

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