Avalanche forecast

Northwest Coastal

Mar 13 – 14, 2014Avalanche Canada
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Avalanche danger

Sat
Sun
Alpine
4 · High
Treeline
4 · High
Below
3 · Considerable
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Highlights

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely - Certain
    Size
    2–5
    Heavy snowfall and strong winds continue to build widespread reactive storm slabs. In many areas this slab sits on a weak layer from early March. Expect stiffer wind slabs in lee features.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    3–7
    The weak layer from early Feb is down roughly 1.5m and continues to be reactive in isolated areas. Heavy triggers such as storm avalanches or cornice falls have the potential to trigger this deep layer which would resulting in very large avalanches.

Confidence

Fair - Intensity of incoming weather systems is uncertain

Weather Forecast

The next storm system hits the north coast on Thursday night or Friday morning. A bit of a break is expected for Friday night before the second system arrives Saturday morning. The second system is expected to be stronger and should last until Sunday night. The south of the region can expect greater snowfall amounts than the north. There is a fair amount of uncertainty regarding freezing levels.Thurs. Night/Friday: Snow 15-30cm, freezing levels up to ~1000m, ridgetop wind 20-40 km/h SWSaturday: Moderate to heavy snowfall, freezing levels up to ~1000m, ridgetop wind 40-60 km/h SE-SWSunday: Moderate to heavy snowfall, ridgetop wind 40-60 km/h SE-SW

Avalanche Summary

Widespread natural avalanche activity was reported on Wednesday. Avalanches up to size 3.5 are being reported across the region and one size 4 was reported at the north end of the region. Avalanches are running within the storm snow, on the March weak layer down 60-100cm, and also stepping down to the Feb weak layer which is typically down around 1.5m but may be as deep as 2.5m.

Snowpack Summary

Storm slabs continue to build. At the end of the last storm pulse, the storm slab was up to 1m thick in the north of the region, . The south of the region had less snowfall and the slab is roughly 60cm thick. These slabs generally sit on a weak layer which may consist of any of the following: hard wind slabs or wind-scoured slopes in exposed terrain, a thick layer of faceted snow on sheltered, shady slopes, isolated surface hoar on sheltered, shady slopes, and sun crust on steep solar aspects. Expect moist or wet snow below roughly 1000m elevation. The mid February weak layer of surface hoar or a crust/facet combo is typically buried over 1.5m deep. This layer continues to react in snowpack tests, primarily on sheltered north aspects at or below treeline. The weight of the new snow and rain has the potential to reactivate this layer resulting in large, destructive avalanches. Basal facets and/or depth hoar remain an isolated concern in shallow snowpack areas in the northern part of the region.

Regions covered