Bulletin d’avalanche

Northwest Inland

Jan 26 – 28, 2020Avalanche Canada
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Archivé · expiré 7 years ago

Danger d’avalanche

Tue
Wed
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible

Points saillants

Triggering avalanches remains possible where strong winds have drifted the recent snow into slabs at higher elevations. Seek out sheltered slopes or monitor for these conditions if travelling in wind-exposed areas.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    15-30 cm of recent snow has been blown into wind slabs on north through east aspect slopes in exposed areas. The new snow buried an interface of weak, sugary facets that may be more prone to human triggering.

Weather Forecast

Sunday night: Cloudy, 2-5 cm of snow, moderate southwest winds, gusting strong, alpine temperature -4 C, freezing level around 600 m.

Monday: Mostly cloudy, 2-5 cm of snow, moderate southwest winds, alpine high temperature -6 C, freezing level around 500 m.

Tuesday: Mix of sun and cloud, a trace of snow, moderate southwest winds, alpine high temperature -5 C, freezing level at valley bottom.

Wednesday: Cloudy, 5-15 cm of snow, strong southwest wind, alpine high temperature -2 C, freezing level around 600 m.

Confidence

Moderate - Uncertainty is due to the limited number of field observations.

Avalanche Summary

Several natural and human-triggered wind slab avalanches were reported over the weekend (up to size 2.5). Over the past week, there have been reports of storm slabs (up to size 2) releasing on a faceted interface from mid-January (see an example in this MIN report).

There have been reports trickling in over the past month of natural persistent slab avalanches up to size 3 in the Bulkley Valley. These are thought to have been failing on the November crust/facet layer near the ground. The last reported activity at this interface was Monday January 13th.

Snowpack Summary

South winds have drifted the recent 15-30 cm of snow (up to 50 cm in the Howson area) into slabs near and above tree line. These slabs sit on previously scoured surfaces from the arctic outflow winds or a weak layer of facets.

A layer of surface hoar now buried up to 1 m below the surface may also be found at treeline. A deep crust/facet layer lurks at the base of the snowpack. A couple of large avalanches are suspected to have run on this interface in the last few weeks. These larger avalanches have been specific to lee and cross-loaded features in the alpine.

Terrain and Travel

  • Expect slab conditions to change drastically as you move into wind exposed terrain.
  • Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
  • Stay off recently wind loaded slopes until they have had a chance to stabilize.

Régions couvertes