Avalanche forecast

Northwest Coastal

Mar 14 – 15, 2017Avalanche Canada
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Avalanche danger

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

Stormy wet and windy conditions continue. Storm slabs continue to grow in the alpine and natural avalanches are expected.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    2–4
    The natural storm slab cycle is expected to release persistent slab avalanches. Cornice falls may trigger deeply buried persistent weak layers.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    2–3
    Storm slab avalanches are expected to continue due to forecast snow and wind.

  • Wet Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–3
    Heavy rain on snow may trigger wet slab or loose wet avalanches at lower elevations. This problem may be short lived due to the forecast cooling trend.

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain on Wednesday

Weather Forecast

Overnight: The storm continues and freezing levels drop down to 500 metres by morning. This will result in 10-15 cm of new snow combined with strong southwest winds. Wednesday: Another 15-20 cm of new snow above 700 metres with moderate southwest winds. Thursday: A bit cooler with daytime freezing levels around 500 metres, moderate southerly winds and 5-10 cm of new snow. Friday: Strong southwest winds and 10-15 cm of new snow.

Avalanche Summary

Several wet slab avalanches size 2.5 were reported on Tuesday from the Bear Pass area. I suspect that a natural avalanches cycle is ongoing today. Reports may be limited by poor visibility and travel conditions.

Snowpack Summary

Storm slabs continue to develop above 1100 metres. These storm slabs are deep 30-60 cm, with much deeper areas where the wind has transported the snow. Below 1100 metres the snow is moist or wet. The overall results will be widespread touchy storm slabs at higher elevations and unstable wet snow at lower elevations. The storm snow is also stressing a weak interface from February composed of facets, crust, and surface hoar buried over a metre deep. Given the recent activity on this layer before the storm, it should be very reactive during this storm. The lower snowpack is strong, with the exception of basal facets in shallow snowpack areas around Bear Pass and Ningunsaw.

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