Avalanche forecast

Northwest Coastal

Apr 7 – 8, 2014Avalanche Canada
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Avalanche danger

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

The ongoing storm will pack a punch and is driving the Danger Ratings. The snowpack does not typically handle rapid change well and deeply buried persistent weak layers may re-awaken.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1–5
    New snow driven by strong ridge top winds will likely build thick storm and wind slab problems at and above treeline. The new snow will likely have a poor bond and  is expected to be unstable initiating large-very large avalanches.

  • Wet Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–4
    At lower elevations the snowpack will likely become saturated and weak with heavy rainfall. Wet slab avalanches typically move slower, however they are very destructive and can mow down anything in their path.

  • 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

As the warm front heads north the associated cold front will move across the region tonight bringing continued heavy-moderate precipitation, extreme to strong SW winds and lowering freezing levels.Monday night: Snow amounts up to 15 cm. Ridgetop winds strong-extreme from the SW. Freezing levels falling to 600 m. Tuesday: Snow amounts 10-15 cm. Ridgetop winds strong from the SW. Freezing levels rising to 800 m. Wednesday: Snow accumulations up to 30 cm. Ridgetop winds strong from the SW. Freezing levels near 700 m.Thursday: Moderate precipitation for coastal areas, and light inland. Ridgetop winds generally light from the SW with strong gusts. Freezing levels 1000 m.

Avalanche Summary

Expect a widespread natural avalanche cycle to continue at all elevations on Tuesday. It will take a couple of days before things start to settle out. Travel in avalanche terrain is not recommended.

Snowpack Summary

Up to 30 cm (25-35 mm) of new snow fell overnight Sunday at upper elevations forming new storm slabs. Strong southerly winds has transported the new snow building thick wind slabs on leeward features and potentially overloading persistent weak layers that exist lower in the snowpack. I suspect cornices have grown large. At lower elevations the snowpack will likely become saturated 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 - 100cm and is composed of facets/surface hoar on shady aspects and facets/crust on southerly aspects. The early February crust/facet/surface hoar combo is down 150 - 200cm. This layer was responsible for a couple of unexpected large avalanches right at the end of March and the beginning of April. These layers should be on your radar and could become reactive with intense loading from rain/snow, warm temperatures and strong winds.

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