Avalanche forecast

South Columbia

Mar 19 – 20, 2017Avalanche Canada
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Avalanche danger

Tue
Wed
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

We've weathered the storm but we're not out of the woods yet. There's a great blog post on critical factors to watch out for this spring. Click here for details.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–4
    Various persistent weaknesses 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
    Possible - Likely
    Size
    1–3
    Warm storm snow on Saturday combined with strong southwest wind created a touchy storm slab problem. The snowpack will need time to adjust to the new load - stick to low angled terrain (with no overhead hazard) and avoid sunny slopes on Monday.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

Clear and cool on Monday and then some clouds move in (with isolated flurries) for the rest of the forecast period.MONDAY: Sunny with increasing cloud in the afternoon / Light east wind / Alpine temperature -6 / Freezing level 1200mTUESDAY: Isolated flurries / Light to moderate southwest wind / Freezing level 1500mWEDNESDAY: Broken skies with isolated flurries / moderate south wind /Freezing level 1600m

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 ; a Size 3.5 natural running to ground on a west aspect at 1900m on Sunday... every day one or two spooky large avalanches in this region. Many of the recent 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 strong to extreme 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 30-60cm above 1600m) 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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