Avalanche forecast

Sea To Sky

Mar 13 – 14, 2012Avalanche Canada
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Avalanche danger

Thu
Fri
Alpine
4 · High
Treeline
4 · High
Below
4 · High
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Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1–6
    Wind slabs lurk below ridges, behind terrain features and in gullies. Extreme wind speeds on Monday may have left slabs unusually low on the slope or in openings below treeline. These could be hidden by 30-40cm of dry snow, making them hard to spot.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    4–8
    Persistent weaknesses, now about 1.5m deep, demand respect. The potential for remote triggering, step down avalanches, and wide propagations makes this persistent slab problem particularly intimidating and tricky to manage.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely - Certain
    Size
    1–6
    Storm slabs are building ever deeper with successive weather systems and are failing under their own weight. They are also overloading persistent weak layers.

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain for the entire period

Weather Forecast

The timing and intensity of a series of fronts affecting the area is uncertain. The general picture is for the rest of the week to be stormy.Wednesday: Cloudy, with snow developing in the morning and continuing overnight. Freezing level around 1000m. Moderate to strong south-westerly winds. Thursday: Heavy snow. Moderate to strong south-easterly winds. Freezing level around 1500m.Friday: More snow. Freezing level falling to around 1000m.

Avalanche Summary

It's been an active week for avalanche activity and the cycle is expected to continue. On Monday, a skier was partially buried and two others escaped a size 2 slab on an east aspect at 1500m, which failed on a crust. Natural and skier-remote triggered avalanches to size 3 were also observed on a variety of aspects and elevations, some failing on the mid-February weakness. Crowns were up to 150cm deep. Every day of the last week, avalanches have been triggered either naturally, remotely or accidentally by backcountry travellers. Conditions are not expected to improve quickly.

Snowpack Summary

Stormy conditions are creating ever-deeper wind slabs and storm slabs. The upper snowpack is like a club sandwich with layers of new wind slab, storm snow layers of variable density, old moist snow and hard old wind slabs. Storm slabs or wind slabs may step down and trigger a deep weakness, formed in mid-February. On Monday, reports of avalanches failing on this layer naturally and with a remote trigger started coming in. Very large avalanches are possible, which could be remote-triggered, triggered mid-slope, and/or propagate into low-angled terrain.

Regions covered