Boletín de aludes

Purcells

Jan 3 – 4, 2021Avalanche Canada
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Archivado · caducó 6 years ago

Peligro de aludes

Tue
Wed
Alta montaña
3 · Notable
Límite del bosque
3 · Notable
Bajo el límite
3 · Notable
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Lo esencial

  

New snow and strong southwesterly winds overnight will form reactive wind slabs on lee features at treeline and above. Concern remains for human triggering of large avalanches on deeper weak layers.

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1.5–2.5

    Wind slabs in motion may step down to deeper weak layers, resulting in large avalanches.

  • Persistent Slabs

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

    A weak layer of surface hoar down 50-100 cm. has been reactive to human triggers, resulting in large avalanches.

  • Deep Persistent Slabs

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

    A Crust buried near the bottom of the snowpack has been responsible for some very large explosive triggered avalanches up to size 4.

Confidence

Moderate - Uncertainty is due to the limited number of field observations. Forecast precipitation (either snow or rain) amounts are uncertain.

Weather Forecast

  

SATURDAY NIGHT: Snow; 5-10 cm. / Strong, southwest ridgetop wind / alpine low temperature -8 / Freezing level 1200 m.

SUNDAY: Flurries; 3-5 cm. / Moderate, west ridgetop wind / alpine high temperature -6 / Freezing level 1300 m.

MONDAY: Cloudy with isolated flurries; 0-3 cm. / Light, southwest ridgetop wind / alpine high temperature -8 / Freezing level 1000 m.

TUESDAY: Mix of sun and cloud / Light, west ridgetop wind / alpine high temperature -7 / Freezing level 1100 m.

Avalanche Summary

On Thursday, a ski cut resulted in a size 2 persistent slab avalanche on a northeast aspect in the alpine near Kicking Horse Mountain Resort. MIN report HERE.

A skier triggered avalanche was reported in the Golden area on Wednesday. Check out the MIN report HERE. The 50 cm failure plane depth matches up with the persistent weak layers discussed in our snowpack summary. The report also suggests that in some areas more recent wind slabs may be quite reactive.

These recent avalanches are a reminder that when persistent slabs are the problem; conservative terrain choices are the answer.

Snowpack Summary

New snow and strong southwest winds will build reactive wind slabs in lee features at treeline and above.

There are currently two layers of concern in much of this region's snowpack. The early December surface hoar is down 30 to 80 cm. Although there have been no new reports of avalanches on this layer in the last few days, it remains possible to human trigger where it is well preserved. There may also be a crust near or instead of this layer in some areas.

The lower snowpack is characterized by more crusts, the most notable is a rain crust from early November that is sitting near the base of the snowpack, surrounded by a weak layer of sugary facets. It is most likely to be reactive to human triggers in steep, shallow, rocky areas with a thin to thick snowpack.

Terrain and Travel

  • Uncertainty is best managed through conservative terrain choices at this time.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.
  • Remote triggering is a concern, watch out for adjacent and overhead slopes.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

Regiones cubiertas