Bulletin d’avalanche

Purcells

Apr 21 – 22, 2021Avalanche Canada
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Archivé · expiré 5 years ago

Danger d’avalanche

Fri
Sat
Alpin
2 · Modéré
Limite forestière
1 · Faible
Sous la limite
1 · Faible
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Points saillants

Be careful around cornices and watch for new snow forming isolated wind slabs in the alpine.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–1.5

    New snow may form isolated pockets of unstable wind slabs in the alpine.

  • Cornices

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

    Minimize your exposure below cornices. Cornice falls are dangerous on their own and can possibly trigger avalanches on slopes below.

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

A cold front crossing the region on Thursday will bring a shift to cooler stormy weather.

WEDNESDAY NIGHT: Increasing clouds, 40 km/h northwest wind, freezing level drops to 1200 m with treeline temperatures dropping to -4 C.

THURSDAY: Cloudy with light flurries bringing up to 5 cm of snow across the region, light northeast wind, freezing level climbs to 1600 m with treeline temperatures around -3 C.

FRIDAY: Cloudy with scattered flurries bringing 5-15 cm of new snow, flurries easing in intensity throughout the day, light southwest wind, freezing level climbs to 1800 m with treeline temperatures around -2 C.

SATURDAY: Cloudy with scattered flurries bringing another 5-10 cm of snow, light southeast wind, freezing level climbs to 1800 m with treeline temperatures around -2 C.

Avalanche Summary

Warm temperatures over the past week resulted in widespread wet avalanche activity, primarily on sun-exposed slopes. Most of the activity was size 1-2 wet loose avalanches, but a few larger and destructive wet slab avalanches were reported (near the Bugaboos on Saturday and near Golden on Monday). Some large cornice falls were also observed.

The cooling trend will make wet avalanches problems less likely in the coming days, making isolated wind slabs and cornice falls the primary concern.

Snowpack Summary

A dusting of new snow will sit above a thick surface crust. The upper snowpack has been undergoing a daily melt-freeze cycle, so with the cooling temperatures a hard crust will form everywhere except in high north-facing terrain where there still may be dry snow above roughly 2300 m. We suspect older weak layers have gone inactive as the weather patterns over the past month have been favourable for strengthening the snowpack.

Terrain and Travel

  • When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.
  • Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
  • Wind slabs may be poorly bonded to the underlying crust.

Régions couvertes