Bulletin d’avalanche

Northwest Inland

Dec 15 – 16, 2011Avalanche Canada
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Archivé · expiré 15 years ago

Danger d’avalanche

Sat
Sun
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
3 · Marqué
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Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–3
    Wind slabs forming on northeasterly aspects. They may be touchy, reactive, and propagate far; especially in areas with a weak buried surface/hoar/facet interface. Loading may occur lower on the slopes due to strong winds in some parts of the region.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely - Very Likely
    Taille
    1–3
    Forecast wind and snow will create storm slabs at all elevations. They will be touchy and reactive especially in areas with a weak buried surface hoar/crust/facet interface. Storm slabs can run fast and be destructive.

Confidence

Fair - Forecast snowfall amounts are uncertain on Saturday

Weather Forecast

Friday: Snow amounts amounts 20-30cm, and rain at lower elevations. Freezing levels are expected to rise to 1600m. Ridgetop winds will be blowing strong from the south then switching south west. Saturday: Light-moderate snow amounts, rising freezing levels during the day, then falling back to valley bottom at night. Sunday: Looks like a break in the systems. Mix of sun and cloud, freezing levels back to valley bottom.

Avalanche Summary

Several size 2 natural avalanches have been reported. These occurred on northerly aspects failing on the SH/CR/FC combo layer. I suspect we will see a natural cycle through the early part of the weekend with more snow and wind forecast.

Snowpack Summary

New surface hoar crystals have formed up to 5mm in size and sits on the recent 20cm of storm snow which is slowly settling. The storm snow we received earlier this week sits on a variety of old weak snow surfaces including surface hoar, melt-freeze crusts and facetted snow (SH/CR/FC). For the most part all aspects between 900m-2000m have a hard melt freeze crust. This crust is widespread and is lingering in most start zones. This is the layer of concern as we receive more snow and wind Friday and Saturday. Above this crust surface hoar (feathery crystals) and facets (sugary crystals) are preserved. This exists at treeline and below treeline elevations. The recent winds in the alpine have destroyed the surface hoar eliminating one problem but creating a wind slab problem. These wind slabs are in the immediate lee of features, sitting on the SH/CR/FC combo. They are reactive and rider triggered avalanches are likely. The midpack seems to be well settled and strong. Thanks to those who have sent in field observations. If you have any info from the field, we would love to hear from you. Write to us at [email protected]

Régions couvertes