Bulletin d’avalanche

South Columbia

Feb 4 – 5, 2022Avalanche Canada
Voir sur la carte
Archivé · expiré 5 years ago

Danger d’avalanche

Sun
Mon
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
3 · Marqué
Ouvrir la carte complète

Points saillants

An incoming storm will load a buried weak layer that has already caught people off guard. Diligent terrain travel and avoidance of suspect features is needed. Treat the hazard as HIGH if you notice signs of instability or find 25+ cm of new snow.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1.5–2.5

    New snow is loading a widespread weak layer of surface hoar crystals found around 40 to 80 cm deep. The layer exists at all elevation bands and has recently been very reactive between 1500 and 2300 m. Example terrain features to particularly treat as suspect include the lee side of ridges, openings in trees, cut blocks, and burns. If triggered, there is potential that an avalanche could step down to a deeply buried weak layer and form very large avalanches.

  • Storm Slabs

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

    New slabs are building as the snow accumulates. Expect to find storm slabs in sheltered areas and wind slabs in wind-exposed terrain. The air is gradually warming, so slabs are expected to develop quickly.

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

THURSDAY NIGHT: Cloudy with snowfall, accumulation 1 to 3 cm, 20 to 40 km/h southwest wind, alpine temperature -8 C.

FRIDAY: Cloudy with snowfall, accumulation 10 to 20 cm, 30 to 50 km/h southwest wind, alpine temperature -6 C.

SATURDAY: Cloudy with snowfall, accumulation 10 to 20 cm, 30 to 50 km/h west wind, alpine temperature -6 C, freezing level rising to 1000 m.

SUNDAY: Mix of sun and cloud with no precipitation, 20 to 40 km/h southwest wind, alpine temperature 0 C, freezing level rising to 2000 m.

Avalanche Summary

Many storm and wind slabs were triggered by riders, explosives, and naturally, with many releasing on the surface hoar layer described in the Snowpack Summary. They often occurred between 1800 and 2300 m and were 30 to 60 cm deep.

Similar slabs are expected to be easily triggered by riders where the recent snow sits on surface hoar crystals. Stay diligent!

Snowpack Summary

Around 10 to 20 cm of snow is forecast to accumulate over the day on Friday, which will form new storm slabs in sheltered terrain and wind slabs in lee terrain features at higher elevations. 

The snow will load a weak layer of surface hoar crystals 5 to 15 mm in size. The layer may be around 40 to 80 cm deep by the end of Friday, which is a prime depth for human triggering. The layer is most prominent in areas sheltered from the wind. Example terrain features to treat as suspect include the lee side of protected ridges, openings in the trees, cut blocks, and burns. The layer may not exist on steep sun-exposed slopes, where a melt-freeze crust may be found instead.

The facet/crust layer that formed in early December is buried around 100 to 200 cm. The last reported avalanche was on January 28 in the north of the region. Although unlikely, the layer could be triggered from a large load like a cornice fall or a shallower slab avalanche could step down to this layer. Humans are unlikely to trigger it, with perhaps the exception in thin, shallow snowpack areas. Check out the forecaster blog for more information.

Terrain and Travel

  • Good day to make conservative terrain choices.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
  • Shooting cracks, whumphs and recent avalanches are strong indicators of an unstable snowpack.
  • Make observations and assess conditions continually as you travel.
  • Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
  • Watch for fresh storm slabs building throughout the day.

Régions couvertes