Bulletin d’avalanche

Purcells

Feb 3 – 4, 2023Avalanche Canada
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Archivé · expiré 4 years ago

Danger d’avalanche

Sun
Mon
Alpin
3 · Marqué
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Points saillants

The snowpack remains weak, requiring diligent terrain travel for a safe day.

Problèmes avalancheux

  • Wind Slabs

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

    Wind slabs may linger in lee terrain features, particularly where they overly surface hoar crystals. If triggered, wind slabs could step down to deeper weak layers.

  • Persistent Slabs

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

    Several weak layers sit in the upper and middle portions of the snowpack at prime depths for human triggering. Stay disciplined and choose low consequence lines, particularly in steep wind-sheltered terrain where these layers may be most problematic.

  • Deep Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2.5–4

    It remans possible that riders could trigger a weak layer of facets near the base of the snowpack. The most likely area to trigger it is in shallow areas with variable snow depths. Avoid thin and rocky start zones and select routes that avoid exposure to large avalanche paths.

Terrain and Travel Advice

  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
  • Surface hoar distribution is highly variable. Avoid generalizing your observations.
  • Approach lee and cross-loaded slopes with caution.
  • Uncertainty is best managed through conservative terrain choices at this time.

Confidence

Moderate

Avalanche Summary

A few large (size 2) persistent slab avalanches were triggered by explosives over the past couple days, releasing about 40 cm deep in alpine terrain. Small wind slabs continue to be triggered by riders and with explosives, most in the western part of the region.

Looking forward, similar avalanches could be triggered by riders on Friday. The possibility remains of triggering facets near the base of the snowpack, particularly on shallow, rocky slopes.

Snowpack Summary

Wind slabs of approximately 20 cm thick may linger on a variety of surfaces including previously wind-affected snow, a small layer of surface hoar, and a melt-freeze crust on sun-exposed slopes.

The mid-pack contains two layers that remain a concern. The first is buried about 20 to 40 cm and consists of a layer of surface hoar from early January. The second is a layer of surface hoar, facets, and crust buried about 40 to 60 cm.

A layer from late November is found 70 to 130 cm deep and is part of a generally weak faceted snowpack.

Snowpack depths range between 80 and 180 cm at treeline, with the shallowest depths found in the eastern part of the region.

Weather Summary

Thursday Night

Clear skies with no precipitation, 20 km/h southwest wind, treeline temperatures -5 °C.

Friday

Mix of sun and cloud with trace snowfall late afternoon, 20 km/h southwest wind, treeline temperature -4 °C.

Saturday

Cloudy with snowfall, accumulation 2 to 5 cm, 20 km/h southwest wind, treeline temperature -4 °C.

Sunday

Cloudy with intermittent snowfall, accumulation 1 to 3 cm, 10 to 20 km/h west wind, treeline temperature -4 °C.

More details can be found in the Mountain Weather Forecast.

Régions couvertes