Bulletin d’avalanche

Northwest Coastal

Jan 24 – 25, 2015Avalanche Canada
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Archivé · expiré 12 years ago

Danger d’avalanche

Mon
Tue
Alpin
4 · Fort
Limite forestière
4 · Fort
Sous la limite
3 · Marqué
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Points saillants

Intense loading from new wind and snow will add more stress to buried weak crystals, and very large avalanches remain a real concern. Conservative terrain selection remains critical.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    3–6
    About 100cm of recent storm snow overlies weak crystals which formed in early January. In recent days, very large avalanches were observed on these layers, and human triggering remains a very real concern.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely - Very Likely
    Taille
    1–4
    Recent heavy loading from snow and wind has created potent new storm slabs at higher elevations. Watch for increased reactivity in wind-exposed terrain. At lower elevations where rain has fallen, destructive wet slabs are also possible.

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1–3
    The snowpack is saturated at elevations where rain has fallen. Pushy loose wet avalanches are a concern in steep terrain.

Confidence

Fair - Intensity of incoming weather systems is uncertain

Weather Forecast

A steady pacific moisture stream is aimed at the North Coast, although the track of the system suggests the bulk of the precipitation will initially fall just to the south of the region. Sunday: Up to 10cm of snow at higher elevations / Extreme southwest winds / Freezing levels at 1400m Monday: Up to 15cm of snow at higher elevations / Strong southwest winds / Freezing levels at 1300m Overnight Monday and Tuesday: 15-20cm of snow / Strong southwest winds / Freezing levels at 800m

Avalanche Summary

Very heavy loading from snow, wind, and rain has resulted in a widespread natural avalanche cycle up to size 4.0 on Thursday. Reports from Wednesday include numerous wind slab and some step-down persistent slab avalanches in the Size 2-3 range, with isolated deep persistent slab avalanches up to size 3.5 from large alpine features. Below approximately 1000m numerous wet loose snow avalanches up to Size 2.5 were observed running in steep terrain. This pattern should continue throughout the forecast period.

Snowpack Summary

Heavy snowfall (with rain below approximately 1500-1000 m) and strong southwest winds have built fresh deep and dense storm and wind slabs. The slabs are likely 'upside down' with warm temperatures dropping moist dense snow on previous dry lower-density snow. A rain crust and/or surface hoar layer buried mid-January is down around a metre. Recent reports mention that this weakness has become 'electric' with recent heavy loading and has been responsible for much of the recent large avalanche activity. The November crust near the bottom of the snowpack is generally well bonded, but may 'wake up' with intense loading this week. There is potential for isolated very large and deep avalanches.

Régions couvertes