Avalanche forecast

Sea To Sky

Mar 16 – 17, 2012Avalanche Canada
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Avalanche danger

Sun
Mon
Alpine
4 · High
Treeline
3 · Considerable
Below
3 · Considerable
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Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–6
    Wind slabs lurk below ridges, behind terrain features and in gullies. Strong winds may create slabs unusually low on the slope or in openings below treeline.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    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
    Likely - Very Likely
    Size
    1–6
    Up to 180 cm of storm snow has fallen in the past week. Storm slabs are touchy, and exist at all elevations. It may take several days for the new snow to settle. They are also overloading persistent weak layers.

Confidence

Good

Weather Forecast

An unstable air mass will bring mainly cloudy skies and light snow amounts through the weekend, with freezing levels remaining at or near the valley bottom. If the sun shines through, solar radiation will be strong. Saturday: Snow amounts 5-10 cm. Ridgetop winds light gusting moderate from the South. Alpine temperatures near -5. Freezing levels 700 m. Sunday: Overcast with light snow amounts in the morning. Winds will be light from the NW. Freezing levels at valley bottom. Monday: A weak ridge of high pressure will bring dry, cooling conditions and light Southerly winds. Solar radiation may be strong if the sun shines through.

Avalanche Summary

Reports of natural size 2-3 avalanches came in on Thursday. These occurred on a variety of aspects. Numerous reports of skier triggered and explosive triggered avalanches up to size 1.5 were also received. These occurred within the recent storm snow on N-SE aspects. On Tuesday a natural avalanche cycle occurred up to size 3 on N-NE aspects. Cornices reached their threshold and triggered slopes up to size 2.5 below. 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. Unsettled weather conditions continue. It may take several days for all this new storm snow to settle out. If the sun shines through in your local mountains; expect strong solar radiation, snowpack deterioration, and elevated avalanche danger.

Snowpack Summary

In the past week 100-180 cm storm snow has fallen, accompanied by strong SW winds. Storm slabs and wind slabs continue to build. Cornices are large, some reaching threshold and triggering the slopes below. For the most part, the new storm snow is right side up (lower density snow on top) and easy to moderate shears exist within the upper meter. The additional weight of new storm and wind slabs may step down and trigger a deep weakness, formed in mid-February. Recent test results on this layer produced hard sudden planar results down 120cm in the snowpack (DTH24 SP dwn 120cm on FC/RG 0.5). Very large avalanches are possible, which could be remote-triggered, triggered mid-slope, and/or propagate into low-angled terrain. The average snowpack depth at treeline is 350 cm.

Regions covered