Bulletin d’avalanche

North Columbia

Mar 31 – Apr 1, 2017Avalanche Canada
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Archivé · expiré 10 years ago

Danger d’avalanche

Sun
Mon
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Points saillants

A complex mix of avalanche problems is maintaining elevated danger in the region. The potential for a storm slab or cornice release to trigger a deeper persistent slab remains a real concern for Saturday.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2–4
    A cornice fall or smaller slab avalanches could trigger deep, destructive avalanches on buried weak layers. There is a low likelihood of triggering but a high consequence if triggered. These avalanches would likely run full path.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–3
    New storm snow and wind have formed storm slabs that are likely to remain reactive to human triggering on Saturday. Cornices have also grown large and fragile. These may fail with daytime warming or during stormy periods.

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1–2
    Daytime warming and rain will deteriorate the lower elevation snowpack on Saturday. This has the potential to initiate loose wet avalanches that may slide easily on a buried crust.

Confidence

Moderate -

Weather Forecast

Friday night: Flurries bringing up to 5 cm of new snow. Light to moderate south winds. Saturday: Cloudy with continuing flurries bringing 5-10 cm of new snow. Light to moderate southwest winds. Freezing level to 1700 metres with alpine temperatures of -4.Sunday: Mainly cloudy with scattered flurries bringing up to 5 cm of new snow. Light west winds. Freezing level to 1400 metres with alpine temperatures of -6.Monday: A mix of sun and cloud. Light northwest winds. Freezing level to 1500 metres with alpine temperatures of -5.

Avalanche Summary

Reports from Thursday include numerous observations of storm slabs releasing naturally from Size 1-2.5 throughout the region. Natural triggers (including natural cornice fall) featured prominently in reports. Crown fractures generally ranged from 30-40 cm and northeast to northwest aspects were the most active.On Wednesday, numerous storm slabs up to size 2.5 were observed. Several size 1 storm and wind slabs were also reactive to rider triggering.

Snowpack Summary

30-50 cm of recent storm snow has accumulated at upper elevations. The new snow is dry up high and moist from 1800 m and below. This now brings 80-120 cm of accumulated snow which overlies a rain crust below 2000 m or a sun crust on solar aspects at higher elevations. New wind slabs are developing on leeward slopes and behind terrain features and large, fragile cornices exist along ridgelines. At higher elevations, the February weak layers are down 150-190 cm and woke up during last week's storm with many avalanches stepping down to them. The deep mid-December facet layer and November rain crust both still linger near the bottom of the snowpack and a few avalanches and cornice falls have also stepped down to these layers last week resulting in some very large full depth avalanches. These layers remain a real concern while touchier storm slabs and cornices continue to present the risk of acting as a trigger for deeper weaknesses.

Régions couvertes