Avalanche forecast

Northwest Coastal

Apr 7 – 8, 2016Avalanche Canada
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Avalanche danger

Sat
Sun
Alpine
No rating
Treeline
No rating
Below
No rating
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Highlights

Spring conditions typically mean the hazard is highest during the heat of the afternoon. Cornices and loose wet sluffing are typical spring problems which can be expected on Friday. Wind slabs may also be a concern in high elevation leeward terrain.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–4
    New snow and strong winds on Friday may build thin new wind slabs. Old wind slabs may also still be lingering and reactive to human-triggering.

  • Cornices

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–5
    Lingering cornices are expected to be weak and may be easily human-triggered. Natural cornice release may occur during storm loading. They can be destructive by themselves, and could become the trigger for a large slab avalanche on the slope below.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–3
    Natural sluffing is possible during periods of rainfall or if the sun makes an appearance. Skier triggering is possible on steep slopes where wet snow overlies a crust.

Weather Forecast

A weak storm system is expected for Friday. 4-8mm of precipitation is expected with freezing levels dropping to around 1300m in the afternoon. Moderate to strong southerly winds are expected in the alpine. Mostly sunny conditions are expected for Saturday with light alpine wind and freezing levels climbing to around 2000m in the afternoon. A mix of sun and cloud is forecast for Sunday with light alpine wind and afternoon freezing levels around 2000m.

Avalanche Summary

Stormy weather has limited recent avalanche observations, although I'm sure there was a decent round of natural storm slab activity in response to new snow and wind on Tuesday. Wind slabs are concern on Friday in high elevation terrain. Cornices are also expected to be weak right now and wet sluffing is possible at lower elevations that see rainfall.

Snowpack Summary

On Tuesday between 25 and 45cm of new snow fell with highest accumulations noted in the south of the region. Extreme westerly winds throughout the storm promoted continued cornice growth and created a widespread wind effect at higher elevations. About 35-60cm below the surface you'll find a widespread hard melt-freeze crust that formed as a result of last week's warm weather and more recent cooling. A few deeply buried weak layers exist within the snowpack including a widespread crust/facet layer buried in early February down around 1.5 m and weak basal facets at the bottom of the snowpack. The near-surface crust has dramatically limited the reactivity of these destructive old layers; however, they have the potential for isolated yet very large avalanches with forecast warming and solar radiation.

Regions covered