Avalanche forecast

South Columbia

Mar 1 – 2, 2013Avalanche Canada
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Avalanche danger

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

While the storm has eased somewhat, it isn't over yet. Dangerous conditions remain in the backcountry.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    3–8
    Numerous large avalanches are failing on a weak and reactive layer of surface hoar which now lies 100cm or more below the surface. Triggering this weakness will result in large and dangerous avalanches.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    3–7
    Expect natural avalanches to run during periods of rapid loading by new snow and wind. Due to the presence of a deeply buried weak layer, the potential size of avalanches could be very large.

Confidence

Fair - Intensity of incoming weather is uncertain

Weather Forecast

Synopsis: A short-lived lull in precipitation is likely for Saturday, before it resumes Saturday night and into Sunday. By Monday, things should dry out.Friday night: 10-15 cm/mm snow/rain.Saturday: Only light amounts are expected during the day, except perhaps for the far north of the region. Snowfall starting again in the evening. Freezing level dropping from 1500 m in the morning to around 800 m in the afternoon. Winds southwesterly up to 40 km/h.Sunday: 5-10 cm new snow. Freezing level around 900 m. Northwesterly winds to 30 km/h.Monday: Dry, with some good sunshine. Cold in the morning, freezing level rising to 1000 m in the afternoon. Light winds.

Avalanche Summary

A widespread avalanche cycle occurred on Friday with preliminary reports of avalanches running up to size 4. Avalanche activity appears to have been more pronounced in the north of the region. Due to the lack of observers in the mountains today, details are limited at this time.

Snowpack Summary

A heavy dump of moist new snow has added to recent storm totals (now 120-150 cm over a two-week period). The snow surface became wet as snow gradually turned to rain to approximately 1800 m. As temperatures drop, expect to see a crust form at lower elevations. Below the storm snow lies a highly reactive weak layer of surface hoar layer (and/or a crust) which was buried on February 12th. Strong southwest winds have redistributed the new snow into deep wind slabs on exposed lee slopes and cross-loaded gully features. The February 12 layer is primed for triggering and has been reacting readily to both natural and human triggers on all aspects and a wide range of elevations. Deeper persistent weak layers from early February and late January continue to show planar failures when moderate to hard forces are applied in snow pack tests. In particular, in the Monashees, a rain crust buried at the end of January approximately 150 cm has been responsible for a couple of recent large, surprising avalanches. During, or immediately following the current storm, the presence of deeper weak layer could further increase the potential size of avalanche events.

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