Avalanche forecast

South Rockies

Mar 18 – 19, 2012Avalanche Canada
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Avalanche danger

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

HIGH avalanche danger is forecast on Monday because of the anticipated effect of sunshine on recent storm snow. Stay away from sunny slopes.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–6
    Wind slabs can be found behind ridges and terrain breaks. Large cornices also threaten slopes below.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    3–8
    Persistent weak layers, now buried 1-2m deep, still have the potential to produce large and dangerous avalanches.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–6
    Recent storm snow may release naturally with the first blast of direct sun. It's possible for surface avalanches to step down to a weak persistent layer, initiating large destructive avalanches.

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain

Weather Forecast

Monday: Mainly sunny with light south-westerly winds. Freezing level rising to around 1300m in the afternoon.Tuesday: Mainly clear in the morning, with clouds and then light (or locally moderate) snow beginning in the afternoon. Winds increasing. Freezing level near 1000m in the afternoon.Wednesday: Light snow continuing. Light to moderate winds. Freezing level near 1000m in the afternoon.

Avalanche Summary

On Sunday, a size 1.5 avalanche released naturally on a north aspect. On Saturday, a recent avalanche was observed on a north aspect in the southern Elk Valley, suspected to have started as a wind slab and ending in moist snow. Evidence of a previous natural cycle was also reported. On Friday, explosives produced size 1-2 avalanches.

Snowpack Summary

Unsettled weather has brought snow and wind through most of the week, creating variable wind slabs and storm slabs. On Saturday, snowpack tests in the Elk Valley, east of Sparwood, showed a couple of shears in the top 20cm of storm snow. A rain crust is buried about 1m down. Two surface hoar layers, buried in February and now 1-2m deep, exhibited sudden planar results, which have been repeated in a number of locations. This means they still have the potential to produce widely-propagating, destructive avalanches if triggered. Most likely triggering mechanisms are a person traveling on a thin snowpack area, or a storm slab, wind slab or cornice stepping down. Basal facets may still exist, particularly in shallow snowpack areas with steep, rocky start zones. Cornices have grown large and threaten slopes below.

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