Bulletin d’avalanche

Northwest Coastal

Apr 9 – 10, 2014Avalanche Canada
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Archivé · expiré 12 years ago

Danger d’avalanche

Fri
Sat
Alpin
4 · Fort
Limite forestière
4 · Fort
Sous la limite
3 · Marqué
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Points saillants

The ongoing storm continues and is driving the Danger Ratings. Deeply buried persistent weak layers have become overloaded.

Problèmes avalancheux

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Very Likely
    Taille
    1–6
    New snow driven by strong ridge top winds have built thick storm and wind slab problems at higher elevations. The new snow likely has a poor bond and is expected to be unstable initiating large-very large avalanches.

  • Wet Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–5
    At lower elevations the snowpack will likely become saturated and weak with heavy rainfall. Wet slab avalanches typically move slower, however they can be destructive and can mow down anything in their path. Smaller loose wet avalanches are likely.

  • Deep Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    3–7
    Persistent weak layers exist in the snowpack. These weak layers could be activated by cornice fall, a surface avalanche in motion, or intense loading from snow, rain and wind. Avalanches failing on these weak layers will be large and destructive.

Confidence

Good

Weather Forecast

Another frontal system over the North Coast will continue to bring moderate precipitation and rising freezing levels 800-1400 m on Thursday/ Friday. The weekend looks to get very warm and sunny.Thursday: Higher elevations could receive up to 30 cm. Rain at lower elevations. Ridgetop winds light gusting strong from the SW. Freezing levels 1300 m.Friday: Snow amounts 5-10 cm on the coast. Mix of sun and cloud inland and in northerly areas. Ridgetop winds moderate from the NE. Freezing levels rising to 900 m. Saturday:  A mix of sun and cloud. Alpine temperatures near 4.0 degrees. Ridgetop winds light from the NE. Freezing levels near 1300 m.

Avalanche Summary

A widespread natural avalanche cycle up to size 4 occurred on Monday and Tuesday and will likely continue through the forecast period. Deep persistent weak layers became overloaded, initiating very-large avalanches. In shallower snowpack areas, storm slab avalanches have stepped down to the December facet/ depth hoar layer. With more precipitation and strong forecast winds, natural avalanche activity will likely persist.

Snowpack Summary

The recent storm has brought 70 cm or more too coastal regions (60-110 mm) forming thick storm slabs and wind slabs on leeward features. Cornices have grown large. At lower elevations the snowpack has become saturated and weak adding to the already spring-like isothermal conditions.Two persistent weak interfaces exist deeper in the snowpack. The early March layer can be found down 75 -140 cm. The early February layer is down 150 - 240 cm. These layers have become overloaded and are failing in some places initiating very-large avalanches.

Régions couvertes