Bulletin d’avalanche

North Columbia

Mar 1 – 2, 2022Avalanche Canada
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Archivé · expiré 5 years ago

Danger d’avalanche

Thu
Fri
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Points saillants

Conservative terrain selection is recommended as the storm snow needs more time to strengthen and there is some uncertainty about buried weak layers.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    2–3

    It may still be possible to trigger large avalanches on one of two weak layers found 50 to 100 cm deep. This includes the mid-February layer (down 40 to 60 cm) and the late-January layer (down 100 cm), both consisting of surface hoar and/or melt-freeze crusts. With increased load from the current storm and warmer temperatures, they have the potential to "wake up" and produce large, unexpected avalanches.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2.5

    Storm slab avalanches are likely in steep terrain at all elevations, as 25 to 45 cm of fresh snow needs time to stabilize. Some natural avalanches are possible on wind loaded slopes in the alpine.

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

MONDAY NIGHT: Cloudy with scattered flurries bringing 5-10 cm of new snow, moderate wind from the southwest, treeline temperatures around -5 C.

TUESDAY: Cloudy with scattered flurries bringing another 5-10 cm of snow, moderate wind from the southwest, treeline temperatures reach -3 C with freezing level climbing to 1500 m.

WEDNESDAY: Mix of sun and cloud, light wind from the south, treeline temperatures around -5 C with freezing level climbing to 1200 m.

THURSDAY: Mostly cloudy with scattered flurries bringing 5-10 cm of snow, light wind from the north, treeline temperatures around -7 C.

Avalanche Summary

Reports from the beginning of the storm on Sunday suggest there were widespread natural and human triggered storm slabs across the region. They were mostly small (size 1) in the top 20 cm of new snow, as shown by the avalanche photo in this MIN report north of Revelstoke. We suspect larger storm slab avalanches occurred on Monday as the storm continued, and these slabs will remain reactive to human triggering on Tuesday.

The last report of a persistent slab avalanche was on Feb 20, which was a size 2.5 avalanche triggered by a cornice. While persistent slab activity has declined, we are uncertain about how persistent weak layers will react to the weight of the new snow.

Snowpack Summary

As the storm trails off on Tuesday expect 25-45 cm of fresh snow. This snow sits above a variety of layers including heavily wind-affected surfaces on alpine slopes, sun crusts on steep south-facing slopes, and some feathery surface hoar crystal in sheltered areas. With mild temperatures and moderate wind in the forecast, expect to find reactive storm slabs at all elevations, with the most reactive slabs on freshly wind loaded slopes. Two potential weak layers exist within the upper snowpack: the mid-February layer (down 40 to 60 cm) and the late-January layer (down 100 cm). They both consist of surface hoar and/or melt-freeze crusts. The reactivity of these layers has declined over the past week.

Terrain and Travel

  • Choose slopes that are well supported and have limited consequence.
  • Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
  • Caution around convexities or sharp changes in terrain.

Régions couvertes