Avalanche forecast

Northwest Coastal

Apr 8 – 9, 2014Avalanche Canada
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Avalanche danger

Thu
Fri
Alpine
4 · High
Treeline
4 · High
Below
4 · High
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Highlights

The ongoing storm continues and is driving the Danger Ratings. The snowpack does not typically handle rapid change well and deeply buried persistent weak layers have become overloaded.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1–6
    New snow driven by strong ridge top winds have built thick storm and wind slab problems at and above treeline. The new snow likely has a poor bond and is expected to be unstable initiating large-very large avalanches.

  • Wet Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    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

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    3–7
    Two buried 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 is targeted for the North Coast Wednesday/ Thursday bringing moderate-heavy precipitation and freezing levels hovering around 800-1200 m.Tuesday night: Snow amounts 5-10 cm. Ridgetop winds strong from the SW. Freezing levels falling to 600 m. Wednesday: Snow amounts 15-25 cm. Ridgetop winds strong from the SW. Freezing levels rising to 800 m. Thursday: Snow accumulations up to 20-25 cm. Ridgetop winds light from the SW gusting strong. Freezing levels near 1000 m.Friday: Unsettled conditions follow the frontal system bringing light-moderate precipitation, light SW winds. An approaching upper ridge will gradually start to dry things out later in the day.

Avalanche Summary

An ongoing, widespread natural avalanche cycle up to size 4 occurred on Monday and will likely continue through the forecast period. Deep persistent weak layers are overloaded in some places, initiating very-large avalanches. Travel in avalanche terrain is not recommended.

Snowpack Summary

The recent storm has brought 50 cm or more too coastal regions (60-100 mm) forming thick storm slabs. Consistent strong southerly winds have transported the new snow building thick wind slabs on leeward features and cornices have grown large. At lower elevations the snowpack has become saturated with rain 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 in some places initiating some very-large avalanches.

Regions covered