Avalanche forecast

South Columbia

Mar 18 – 19, 2017Avalanche Canada
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Avalanche danger

Mon
Tue
Alpine
4 · High
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Rapid loading, warm temperatures and strong wind are a recipe for HIGH danger in the alpine. Avoid avalanche terrain and stay well back from runout zones.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–4
    Various persistent weakness throughout the snowpack create the potential for large step-down avalanches. Heavy loads such as a smaller storm/wind slab avalanche or even a cornice failure will increase the likelihood of triggering these layers.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–3
    More warm storm snow on Saturday combined with moderate to strong wind created a storm slab problem. These storm slabs will be particularly deep and touchy on slopes loaded by southerly wind.

Confidence

Moderate - Intensity of incoming weather systems is uncertain

Weather Forecast

We'll see lingering flurries on Sunday as it cools down significantly. Clearing Monday onwards.SUNDAY: Cloudy with isolated flurries / moderate to strong west wind / Alpine temperature -8 / Freezing level 800mMONDAY: Increasing cloud in the afternoon and some scattered flurries / Light east wind / Alpine temperature -6 / Freezing level 1100mTUESDAY: Isolated flurries (5cm possible)  / Light southerly wind / Freezing level 1500m

Avalanche Summary

The past several days have seen widespread natural avalanche activity at all elevations and on all aspects, including a Size 4.5 in the central Selkirk range reported Thursday (crown height up to 3.5 m high, running 1200 vertical metres and leaving debris up to 28 metres deep) and a Size 3.5 near the Valhallas on a southeast aspect near 2400m.Many of these avalanches ran in the storm snow with some also stepping down to persistent weaknesses (see snowpack summary below) deeper in the snowpack. Widespread wet slabs and loose wet avalanches have also been reported below treeline.

Snowpack Summary

Heavy wet snow (15-20 cm in 12 hours) and moderate southerly winds started late Friday and continued through Saturday. Temperatures also warmed up significantly. The end result: Widespread storm slabs and wind slabs at treeline and above with significant cornice growth as well. All this storm snow (totals of 40-80cm) sits on older windslabs (or soft slabs) at treeline and above. Below 1800m, the new snow sits on a melt-freeze crust from last week's warm storm, and reports so far are that the new snow is bonding well to the old crust. Approximately 100-140 cm below the surface you may find the late-February persistent weakness / crust interface. This layer has woken up from time to time as smaller avalanches still have to potential to 'step down' and trigger this layer. The deep mid-December facet layer (and November raincrust) still linger at the bottom of the snowpack and are the suspected culprit (running to ground) in a Glacier National Park avalanche. See here for the spooky picture.

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