Bulletin d’avalanche

Purcells

Dec 30 – 31, 2015Avalanche Canada
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Archivé · expiré 11 years ago

Danger d’avalanche

Fri
Sat
Alpin
2 · Modéré
Limite forestière
1 · Faible
Sous la limite
1 · Faible
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Points saillants

Riding conditions are excellent right now but isolated problems still exist. Soft wind slabs may still be lingering around ridge crests in the alpine. Sluffing can be expected on steep sun-exposed slopes during the heat of the afternoon.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2
    Wind slabs may still be lurking behind ridges and ribs. Winds have recently changed directions so the problem could exist on either side of a ridge.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely
    Taille
    2–4
    A weak layer buried about 40-100 cm down remains reactive in snowpack tests in some areas. It has produced avalanches within the last week and could wake-up with the upcoming warm temperatures in the alpine.

  • Loose Dry

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1–2
    As the temperatures in the alpine continue to rise, the sun will pack more punch. Loose avalanche activity is expected to continue from steep, rocky, sun-exposed slopes. The volume of dry snow could push you around.

Avalanche Summary

Over the last few days, several small loose dry avalanches and one size 1.5 wind slab have been observed. Persistent slabs were last triggered about a week ago. Unfortunately these types of problems don't heal quickly, so they remain on our radar. This problem may wake up with the upcoming warm temperatures in the alpine.  Progressive warming in the alpine with ongoing sunny conditions should result in ongoing loose natural avalanches from south-facing slopes and by the weekend may create slab properties within the recent storm snow.

Confidence

Moderate - Timing or intensity of solar radiation is uncertain

Weather Forecast

High pressure is the dominant feature for the foreseeable future. In the alpine, sunny conditions are expected for the next few days but most of the valleys will likely to be under valley fog. On Thursday, treeline temperatures will be around -5C with colder temperatures in the valleys. Alpine winds may be moderate from NE in the morning but should ease during the day. On Friday, a layer of above freezing air is expected to invade the alpine. By Saturday, temperatures could be a few degrees above zero from around 2000m to 3000m elevation. On both Friday and Saturday, alpine winds should be light and above the valley fog the conditions should be clear and sunny.

Snowpack Summary

20-30 cm of low-density snow typically overlies a well-settled mid and lower snowpack. Surface hoar and near-surface facets may be mingled within the upper few cm. Storm slab properties may change and become more cohesive as the alpine gets some sun and warmer temperatures. Wind slabs, found in the lee of ridges and ribs, are still reactive in some spots and healing in others.  A weak layer which was buried in early December is down about 40-100 cm. At and below treeline, it mainly consists of large surface hoar. At higher elevations, it consists of a sun crust, facets, and/or small surface hoar. This layer is still reactive in some snowpack tests and has produced at least one human-triggered avalanche in the last week. The persistent slab is a low probability, high consequence problem. Below this layer, the snowpack is thought to be generally strong and well-settled.

Régions couvertes