Avalanche forecast

Northwest Coastal

Jan 21 – 22, 2019Avalanche Canada
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Archived · expired 8 years ago

Avalanche danger

Wed
Thu
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable

Highlights

Winds continue to transport recent snow and load lee features and cross-loaded terrain. Strong winds with more snow and rising freezing levels are expected into Tuesday, the storm slab trend continues.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1.5–2.5
    Winds are redistributing recent snowfall and are expected to increase more snow falls overnight into Tuesday. New wind slabs may hide older wind and storm slabs. Rain and rising freezing levels on Tuesday may weaken the snowpack at lower elevations.

Confidence

Moderate - Intensity of incoming weather systems is uncertain

Weather Forecast

MONDAY NIGHT: Snow, 10-20 cm overnight. South-southwest wind increasing from light to extreme. Alpine low temperature -5C, freezing level rising to 1000 m.TUESDAY: Snow, 5-10 cm with up to 20 cm near Kitimat. Moderate southwest wind gusting strong. Alpine low temperature -4C, freezing level 1000 m.WEDNESDAY: Cloudy with isolated flurries, trace accumulation. Light west wind with moderate gusts. Alpine high temperature +1C, freezing level below 1000 m.THURSDAY: Cloudy with scattered flurries, 5-15 cm accumulation. Light south wind gusting strong. Alpine high +0C, freezing level rising above 1200 m.

Avalanche Summary

There have been no recent avalanche reports around Terrace, however storm slab, wind slab, and loose dry avalanches to size 2 have been reported in the north of the region over the weekend.A MIN report from the Wolfs Den north of Terrace reports strong ridgetop winds redistributing snow and slab properties in the snowpack from Saturday (see the MIN here).Last Wednesday in the far north near Ningunsaw, two large (size 2 and size 3) remotely (from a distance) triggered persistent slabs were observed failing over a 20-50 cm-deep layer of surface hoar over crust. This problem is likely isolated to the far north of the region, but may also exist on sheltered high elevation slopes elsewhere in the region.

Snowpack Summary

20-30 cm recent snow is being redistributed by winds forming slabs and loading snow in lee and cross loaded terrain. This snow covers a variable surface of wind-affected and faceted snow, a weak layer of surface hoar in more protected areas, and a rain crust/surface hoar combination below 1500 m. Warm temperatures are promoting settlement of the snowpack. Rain has saturated the snowpack below 600 m.Below the new snow interface, old wind-affected storm snow is expected to have formed a good bond with the underlying snowpack. An exception to this 'good bond' may exist in some sheltered higher elevations that were unaffected by rain during the last storm. Here, the old storm snow described above may overlie a weak layer of surface hoar (feathery crystals). This layer was identified as the failure plane in several recent large avalanches in the north of the region. It has not shown in reports elsewhere.For most of the region, a weak layer of facets (sugary snow) buried in early December exists down 180-250 cm. The likelihood of triggering this layer is decreasing, but it could be triggered by humans in shallow snowpack areas, particularly in the north of the region.

Regions covered