Bulletin d’avalanche

Purcells

Mar 26 – 27, 2019Avalanche Canada
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Archivé · expiré 8 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

Highly variable snowfall from Tuesday's storm set up an equally variable wind slab problem over the region. Expect new snow to shed easily from steeper slopes as warming and sunshine take effect on Wednesday.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1–1.5
    New snow and south winds are likely to have formed new wind slabs at higher elevations during the storm. This problem increases with elevation and is variable throughout the region due to areas of locally enhanced convective snowfall.

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely - Very Likely
    Taille
    1–1.5
    Rising freezing levels and decreasing cloud cover will signal a return to active loose wet avalanche conditions on Wednesday. Areas with new snow from Tuesday's storm will see new snow shed easily from steep, sun-exposed slopes as warming takes hold.

Confidence

High -

Weather Forecast

Tuesday night: Mainly cloudy with isolated flurries and a trace of new snow. Light west winds shifting to east.Wednesday: A mix of sun and cloud. Light east winds. Alpine high temperatures around -3 with freezing levels to 1800 metres.Thursday: A mix of sun and cloud. Light northeast winds. Alpine high temperatures around -2 with freezing levels to 1900 metres.Friday: Mainly sunny. Light variable winds. Alpine high temperatures around 0 with freezing levels to 2100 metres.

Avalanche Summary

Reports from Monday showed included a few more 12-24 hour old observations of avalanches induced by recent warm temperatures. These included a size 2.5 glide slab at 2200 metres, a size 2 (large) loose wet avalanche at 1900 metres, and several small (size 1) wet slabs at 1250 metres. Looking forward, avalanche danger will remain linked with daytime warming and especially sun exposure. New snow from Tuesday's storm will be the first to shed from steeper slopes as warming takes effect.

Snowpack Summary

Variable new snow amounts of a trace to 20 cm have accumulated above a surface of melt-freeze crust in most areas above 1500 metres, with the exception of limited north aspects above 2000 metres, where it may have landed on the last dry snow that remained after last week's warm up. Below about 1500 metres, it has buried variably isothermal (slushy) and crusty surfaces. Precipitation as rain has continued to saturate the snowpack that is for the most part isothermal and disappearing rapidly below about 1100 metres.The mid snowpack is generally consolidated and strong, but exceptions may exist on north aspects above 2000 m, where a gradually strengthening layer of faceted grains buried 40 to 60 cm deep may still be preserved below an overlying slab of old and hard wind-affected snow.The base of the snowpack is composed of weak faceted snow which may coexist with a melt-freeze crust. One very large persistent slab was reported to have failed at this layer during last week's warming event.

Régions couvertes