Avalanche forecast

Cariboos

Mar 3 – 4, 2012Avalanche Canada
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Avalanche danger

Mon
Tue
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
    Large amounts of available snow and strong winds are likely to create widespread wind slabs, even at treeline. Large cornices also threaten many slopes.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2–8
    Persistent weaknesses in the upper snowpack are unpredictable and tricky to manage. As they become overloaded by new snow, large avalanches could fail on these layers, even on surprisingly low-angled or previously ridden slopes.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1–6
    Storm slab weaknesses are developing as snow falls with fluctuating temperatures. These could fail on a persistent weak layer, creating surprisingly large avalanches.

Confidence

Good

Weather Forecast

Sunday: Moderate to heavy snow. Freezing level 500m, rising to 1000m by afternoon. Strong south-westerly winds.Monday: Moderate snow. Freezing level valley bottom. Light to moderate north-westerly winds.Tuesday: Light snow. Freezing level valley bottom. Light to moderate westerly winds.

Avalanche Summary

As I write this, it's still too early for reports of storm-related avalanche activity, but I expect a natural cycle is well under way. Occurrences throughout the week illustrate the unpredictable nature of persistent weak layers in the upper snowpack. On Thursday, a skier triggered a size 2.5 slab very easily and very close to recent ski tracks, which failed on buried surface hoar. On Wednesday, a cornice fall triggered a size 2 slab on a north aspect, which failed on the Feb 16. weakness. On Tuesday, numerous size 2-3 avalanches ran naturally, or with a remote trigger, on a variety of slopes. Most failed on upper snowpack persistent weaknesses. These layers are touchy and are likely to fail under the new storm load, creating large or widely-propagating avalanches.

Snowpack Summary

Snow is falling with strengthening winds and rising temperatures onto variable surfaces including surface hoar and facets. This is creating a nice recipe for new storm slab and wind slab instabilities. Persistent weak layers buried in February are a key concern at all elevations and could be triggered by storm slabs, wind slabs or sluffs, or with a light additional load (like you). Avalanches may be unexpectedly large, given the amount of fresh snow. Large cornices also loom as potential triggers for deep avalanches.

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