Bulletin d’avalanche

Northwest Coastal

Apr 16 – 17, 2015Avalanche Canada
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Archivé · expiré 11 years ago

Danger d’avalanche

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

Tricky winter conditions exist at higher elevations. Localized solar radiation, snow and winds will destabilize the snowpack. Use a conservative approach to terrain and watch for signs of instabilities.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    3–5
    Additional storm snow loading on the mid- March persistent weak layer has brought it back to life. Smaller storm slab avalanches may step down to this layer, initiating large, destructive avalanches.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely - Very Likely
    Taille
    1–4
    Storm slabs are touchy, especially where they sit on a buried facet, surface hoar and/ or crust interface. Strong winds have built touchy wind slabs on leeward slopes and behind terrain features. Human triggering is likely.

Confidence

Fair - Due to the number of field observations

Weather Forecast

The next pacific front hits the North and Central coast Thursday evening bringing anywhere from 5-15 mm.  Lingering cloud, periods of sunshine and convective snowfall may occur on Friday. Ridgetop winds will be light from the West and freezing levels near 1100 m. Saturday and Sunday will be mostly cloudy with light precipitation. Ridgetop winds will be light from SW and freezing levels rising to 1300 m Saturday. Warm moist air will reach the North on Sunday and freezing levels will rise to 2300 m.

Avalanche Summary

On Wednesday, numerous size 1.5 slab avalanches were reported. They failed on NW-N aspects above 1400 m. On Tuesday, the region saw a natural cycle up to size 3 was from steep alpine and treeline terrain. Suspect some of these naturals are stepping down to the old interfaces buried April 9 th and mid- March. With continued snow, rain, and strong winds natural avalanches and human triggered avalanches will likely continue. Lower elevations  have become rain soaked and natural loose wet avalanches from steeper terrain features are expected.

Snowpack Summary

At upper elevations 35- 80 cm of settling storm snow has blanketed the region. The new snow has been redistributed by strong south-west winds into wind slabs on leeward slopes and terrain features. The lack of bond between the new wind slabs and storm slabs over the older snow surfaces buried on April 9 th (surface hoar, crusts and facets) is the primary concern. The March 25th persistent surface hoar / crust layer is reportedly unreactive, however; with the new load of wind and snow this should remain on your radar as it may re-awaken, initiating very-large and destructive avalanches. Moist- rain soaked snow exists at lower elevations.

Régions couvertes