Bulletin d’avalanche

Purcells

Mar 6 – 7, 2013Avalanche Canada
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Archivé · expiré 14 years ago

Danger d’avalanche

Fri
Sat
Alpin
3 · Marqué
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Points saillants

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1–5
    Recent snow and wind have created new slabs. These may be particularly touchy on slopes lee of the wind and it may take several days for the recent storm snow to settle out. Skier and rider triggering is possible.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2–6
    Persistent weak layers exist buried down 60-100 cm, comprising of surface hoar and a sun crust. Avalanches failing on these layers will likely be large and destructive.

Confidence

Good

Weather Forecast

As the low off the Oregon coast moves inland and South, light-moderate snowfall amounts are expected through Thursday. The low deteriorates by Friday morning and is being replaced by a ridge, bringing dry, sunny conditions with very little wind. Overnight into Thursday: Light-moderate snow accumulations. Ridgetop winds will blow light from the East. Alpine temperatures near -6 and freezing levels at 1300 m.Friday and Saturday: Ridgetop winds will remain light from the NW-N. Alpine temperatures near -5 and freezing levels rising to 1500 m in the afternoon then falling to valley bottom overnight.

Avalanche Summary

No new natural avalanche activity reported. On Tuesday, many operators in the region did control work using explosives and triggered slab avalanches size 1-3 on N-SW aspects generally above 2200 m.

Snowpack Summary

Up to 80 cm of snow fell over the past week and continues to settle. Moderate ridgetop winds have built winds slabs on lee slopes and terrain features. Wind slabs and storm slab instabilities remain, particularly on the west side of the region where accumulations have been highest.Buried beneath (60-100 cm) exists a surface hoar and a sun crust layer, which continue to be lingering concerns. On solar aspects, the sun crust seems to be more reactive. Large looming cornices exist on ridgelines. Cornice fall could trigger a large slab avalanche on the slope below, especially when the sun comes out on Friday.Below treeline exists a melt-freeze crust with moist snow beneath it. The crust may be bridging instabilities deeper in the snowpack. If temperatures warm at lower elevations, you'll notice the crust breaking down and the snowpack becoming weaker.

Régions couvertes