Bulletin d’avalanche

South Columbia

Apr 10 – 11, 2017Avalanche Canada
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Archivé · expiré 9 years ago

Danger d’avalanche

Wed
Thu
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Points saillants

Winter marches on at higher elevations. Wind slabs and cornice falls are the most likely problems. Persistent layers continue to exist in the snowpack, and may become reactive during periods of strong sun or daytime heating.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1–2
    Variable wind directions over the past few days may have developed wind slabs on several aspects in the alpine and at treeline. Forecast new snow may hide recent wind slabs.

  • Cornices

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2–3
    Cornices have grown large and may fall off naturally with solar effect or daytime warming. Cornice falls were responsible for triggering a number of large persistent slab avalanches last week and as recently as Saturday.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely
    Taille
    2–4
    A cornice fall or smaller slab avalanche currently has the potential to trigger large, destructive avalanches on deeply buried weak layers. This is more likely to occur in thin or variable snowpack areas at higher elevations.

Confidence

High -

Weather Forecast

Overnight: 5-8cm of new snow with light westerly winds and freezing down to 600 metres. Tuesday: Another 3-5 cm of new snow with light south winds and daytime freezing up to 1400 metres. Wednesday: A mix of sun and cloud with periods of convective flurries. Daytime freezing up to 1700 metres. Thursday: 5-8 cm of new snow with light southeast winds and daytime freezing up to 1600 metres.

Avalanche Summary

Loose dry and loose wet avalanches to size 1.0 were reported on Sunday. Saturday's reports included details of one Size 2.5 deep persistent slab triggered by a large cornice fall on a north aspect in the Valhallas. Numerous storm slabs were observed releasing naturally in various areas of the region from Size 1.5-2.5, with crown fractures ranging from 30-50 cm and north to northeast aspects seeing the majority of this activity.

Snowpack Summary

5-10 cm of new snow has added to the 30-40 cm of recent snow that blanketed upper elevations of the region late last week. The recent snow sits above a mix of old surfaces that include melt-freeze crusts at treeline and below and on solar aspects in the alpine. Fragile new cornice growth also occurred along ridgelines over the course of the week. Below the new snow interface, a number of storm snow and crust layers that formed over mid to late March appear to be well bonded. The February weak layers are now down about 170-220 cm and the deep mid-December facet layer and November rain crust both still linger near the bottom of the snowpack. These deep weak layers produced large avalanches with cornice falls and other heavy triggers in late March and early April. Yet another deep release was reported in the region on Saturday. This activity, although growing more sporadic, is keeping these layers an ongoing concern. They may be more likely to fail on southerly aspects during periods of strong solar radiation.

Régions couvertes