Bulletin d’avalanche

South Coast Inland

Dec 14 – 15, 2021Avalanche Canada
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Archivé · expiré 5 years ago

Danger d’avalanche

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

The current persistent slab problem is best managed through conservative terrain choices and disciplined backcountry travel techniques.

Avoid likely trigger spots such as steep, rocky terrain, with a shallow or thin to thick snowpack.

Problèmes avalancheux

  • Wind Slabs

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

    70-90 cm of recent snow and strong winds have formed wind slabs on lee features at treeline and above.

  • Persistent Slabs

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

    In the north of the region, a layer of weak facets (sugary snow) can be found down 50-70 cm near a crust that formed in early December. In the neighboring Sea to Sky region, this layer has demonstrated recent instability, and it may be possible to trigger.

Confidence

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast. Uncertainty is due to the limited number of field observations.

Weather Forecast

TUESDAY NIGHT: Partly cloudy / Moderate, southwesterly winds / Low of -12 C / Freezing level surface.

WEDNESDAY: Cloudy / Light, southwesterly winds / High of -5 C / Freezing level 500 m.

THURSDAY: Mix of sun and cloud / Light, northwesterly winds / High of -7 C / Freezing level 200 m.

FRIDAY: Mix of sun and cloud / Moderate, northwesterly winds / High of -9 C / Freezing level surface m.

Avalanche Summary

Check out this recent MIN report of a naturally triggered size 3.5 storm slab avalanche reported on Sunday near Mt. Pierce.

In the neighboring Sea to Sky region, we received recent reports of four large (size 2-2.5) explosive-triggered persistent slab avalanches failing on the early December crust/facet layer. These occurred on northwest and northeast aspects in the alpine.

Snowpack Summary

70-90 cm of recent snow and strong winds have formed wind slabs on lee features at treeline and above.

In the north of the region, weak faceted snow can be found 50-70 cm deep on a crust that formed in early December. This layer has shown reactivity in the neighboring Sea to Sky region. This persistent slab problem warrants careful evaluation and conservative route-finding as the recent snow consolidates into a more cohesive slab over the weak layer.

The south of the region has seen substantially higher snow totals over the past week, with areas near the Coquilhalla seeing over a meter of accumulation since Monday. Expect to find deeper snow accumulations above the December crust and anticipate larger slab avalanches. 

Terrain and Travel

  • Be aware of the potential for large avalanches due to the presence of a persistent slab.
  • Uncertainty is best managed through conservative terrain choices at this time.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

Régions couvertes