Avalanche forecast

Northwest Coastal

Mar 11 – 12, 2017Avalanche Canada
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Avalanche danger

Mon
Tue
Alpine
4 · High
Treeline
4 · High
Below
3 · Considerable
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Highlights

Large avalanches will be widespread for the next few days as the coast gets slammed by a hefty storm.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2–3
    The new snow will likely trigger large avalanches on a reactive weak layer buried 50-80 cm deep.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–2
    Large storms slabs will develop rapidly in the upcoming days.

Confidence

High -

Weather Forecast

SATURDAY NIGHT: Storm intensifying with 10-15 cm of snow and 30-50 km/h south winds.SUNDAY: Stormy with about 20 cm of new snow, 60-80 km/h south winds, alpine temperatures climbing to -5 C.MONDAY: Another 20-30 cm of snow, 70-90 km/h southwest winds, alpine temperatures around 0 C and freezing levels climb to 1000 m.TUESDAY: More snow (15-25 cm), 60-80 km/h south winds, alpine temperatures around -2 C and freezing levels drop to 700 m.

Avalanche Summary

On Friday, wind-loading triggered a size 3 persistent slab avalanche on the February facets on southwest slope. Several cornice and ice falls were reported to entrain loose snow, but did not trigger any slabs. One remotely skier triggered avalanche was reported on a small convexity from 50 m away.The incoming storm has all the ingredients for widespread storm slabs. On top of that, it will also trigger large persistent slab avalanches on buried weak layers.

Snowpack Summary

Expect 20-30 cm of fresh snow on Sunday and thicker, stiffer, and more reactive deposits in lee terrain. The new snow will bury older lingering wind slabs formed by recent outflow winds. The load of the new snow will stress a weak interface buried about 50-80 cm deep composed of facets, crust, and surface hoar. This layer has produced avalanches and alarming snowpack test results on a daily basis for the past week. The lower snowpack is strong, with the exception of basal facets in shallow snowpack areas around Bear Pass and Ningunsaw.

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