Avalanche forecast

Purcells

Apr 12 – 13, 2013Avalanche Canada
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Avalanche danger

Sun
Mon
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Snowfall amounts for Friday night are uncertain. Danger could spike to HIGH by Saturday if we get more than forecast.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    1–6
    A layer of surface hoar is buried about a metre down, mainly on high northerly aspects. A surface avalanche stepping down, cornice fall, or the weight of a person from a thin-spot trigger point could trigger it.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–4
    Snowfall on Friday night is expected to create new storm slabs, especially near ridge top and on slopes in the lee of the wind.

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain for the entire period

Weather Forecast

Saturday: Overnight snowfall tapering off to a cool and unsettled flow with light snow. Moderate W winds. Freezing level around 1000 m.Sunday: Cold and unstable weather, with light snow. Light N winds. Freezing level around 1000 m.Monday: Cold and unstable weather, with light snow. Light or calm winds. Freezing level around 1500 m.

Avalanche Summary

Observations have been limited during Wednesday’s storm, when a natural avalanche cycle is expected to have occurred. On Thursday, a cornice fall triggered a size 2.5 slab. Skiers also triggered size 1 slabs. These events were on NE aspects above 2300 m.

Snowpack Summary

Snowfall on Friday night is expected to create new storm/wind slabs, especially near ridge top. This will add to existing storm slab and wind slab problems at alpine and treeline elevations. A surface hoar interface is buried within the upper metre of the snowpack, mainly on high-elevation northerly aspects. It is still producing moderate, sudden results in snowpack tests, and these slopes should be treated with suspicion. On other slopes, recent storm snow overlies a crust, with a variable bond. At low elevations, previously rain-soaked snow is likely to now be refrozen and strong.

Regions covered