Bulletin d’avalanche

Kootenay Boundary

Dec 29 – 30, 2020Avalanche Canada
Voir sur la carte
Archivé · expiré 6 years ago

Danger d’avalanche

Thu
Fri
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
Ouvrir la carte complète

Points saillants

Keep the presence of a buried weak layer in your mind and continue to choose conservative terrain.

Problèmes avalancheux

  • Persistent Slabs

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

    Weak layers of surface hoar and/or faceted grains overly a hard melt-freeze crust around 60 to 80 cm deep. New snow loads before Christmas pushed the persistent slab problem over the tipping point resulting in large avalanches. Although the likelihood of triggering a persistent slab avalanche is decreasing, the potential for triggering a high consequence avalanche should still be top of mind in your decision making process. 

Confidence

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

Monday night: Mostly dry, light flurries possible. Winds light, northwesterly.

Tuesday: Dry during the day. Treeline temperatures around -9 C. Winds light northwesterly.

Wednesday: 2-5 cm new snow. Treeline temperatures around -8 C. Winds light southerly.

Thursday: 5-10 cm snow ending in the morning. Treeline temperatures around -5 C. Winds light southwesterly.

Avalanche Summary

A couple of skier triggered size 1 avalanches were reported over the weekend, a wind loaded pocket below a roll-over (here) and isolated loose dry sluffs in the new snow.

Many storm and persistent slab avalanches were observed last week across the region. They were generally large (size 2), on west, north, and east aspects, 20 to 70 cm thick, and between 2000 and 2300 m. Although avalanche activity appears to have diminished, I wouldn't rule out the possibility of seeing more persistent slab avalanches.

Snowpack Summary

5-15 cm of recent snow sits over surface hoar in wind sheltered areas. Lingering wind slabs formed last week may remain reactive on a variety of aspects due to shifting winds.

Two weak layers are buried in close proximity to one another, around 50 to 80 cm deep. The layers are composed of feathery surface hoar and sugary faceted grains and they overly a hard melt-freeze crust. Last week saw substantial avalanche activity on these layers from natural and human triggers. Although reports of such avalanches have been dwindling, these weak layers remain a concern, as they can produce large and destructive avalanches.

Terrain and Travel

  • Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.
  • Uncertainty is best managed through conservative terrain choices at this time.

Régions couvertes