Avalanche forecast

Northwest Coastal

Mar 11 – 12, 2014Avalanche Canada
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Avalanche danger

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

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    3–7
    There is potential for heavy loads like a cornice fall or a storm slab avalanches to step down and trigger the persistent weak layer from early-Feb which is typically down 1-1.5m. 

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    2–5
    New storm snow continues to load slopes.  This is adding to the roughly 50cm thick storm slab from the weekend which is sitting on a weak layer.  Stiffer and thicker wind slabs can be expected in lee features from recently strong SW wind.

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

The storm is expected to ease late Wednesday and a ridge will build on Thursday. Another frontal system is expected for Friday but should only result in light precipitation. Tues. Night/Wednesday: Snow or rain 20-25mm, freezing level progressively falling from around 1500m to 700m, ridgetop wind 70-90 km/h SW-W easing during the dayThursday: A mix of sun and cloud, dry conditions, freezing level 500m overnight, 800m afternoon, ridgetop wind light SWFriday: Snow or rain beginning Thursday night 6-10mm, freezing level 700m overnight, 1000m afternoon, ridgetop wind 20-40 km/h SW

Avalanche Summary

Widespread natural activity was reported on the weekend during the first storm but tapered off a bit on Monday during the break between storms. Isolated natural and human-triggered slab avalanches up to size 3 were reported on Monday. More widespread natural activity is expected for late Tuesday and Wednesday during the current storm system.

Snowpack Summary

New storm snow is sitting on the slightly older storm slab that is roughly 50cm thick. These slabs sit on a weak layer which may consist 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 at lower elevations, possibly with one or two new crusts near the surface. The mid February weak layer of surface hoar or a crust/facet combo is buried 1-1.5m deep. This layer continues to react in snowpack tests, primarily on sheltered north aspects at or below treeline. Basal facets and/or depth hoar remain a concern in shallow snowpack areas in the northern part of the region.

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