Avalanche forecast

Purcells

Jan 5, 2019Avalanche Canada
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Archived · expired 8 years ago

Avalanche danger

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

The recent storm snow may take some time to bond and our weak layers will likely need time to strengthen. Conservative route-selection is suggested.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1.5–3
    Substantial amounts of snow fell over the past two days. It may take time for this recent snow to bond, particularly at higher elevations. The touchiest snow may exist in lee terrain features due to wind distribution.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3.5
    The likelihood of triggering deeply buried weak layers is still possible due to recent loading. It may take some time for these weak layers to strengthen with the new load.

Confidence

High -

Weather Forecast

FRIDAY NIGHT: Cloudy with light snowfall, accumulation 5 cm, moderate to strong southwest winds, alpine temperature -3 C, freezing level 1400 m.SATURDAY: Mix of sun and cloud, light southwest winds, alpine temperature -6 C, freezing level 700 m.SUNDAY: Cloudy with light snowfall, accumulation 5 cm, light to moderate southwest winds, alpine temperature -5 C, freezing level 700 m.MONDAY: Mostly cloudy, light southwest winds, alpine temperature -13 C, freezing level below valley bottom.

Avalanche Summary

Evidence of a widespread natural avalanche cycle was observed on Friday. Storm slabs were reactive to skier traffic and explosives, producing large (size 2 to 3) avalanches with depths around 40 cm. A couple avalanches were observed on the deeper layers described in the snowpack summary. There will likely be further observations on what happened during the storm on Saturday as the weather clears up.

Snowpack Summary

The recent storm dropped variable snowfall amounts across the region. In the north, upwards of 100 cm of snow fell. In the remainder of the region, around 40 to 60 cm of snow accumulated. The snow fell with strong westerly winds, so the deepest and touchiest deposits will likely be in lee terrain features. The freezing level rose to around 1500 m on Friday, so expect to find wet snow or a frozen crust below this elevation.All this snow is loading a weak layer that formed during the dry spell in early December. It is around 80 to 120 cm deep. The layer is composed of weak and sugary faceted snow, feathery surface hoar crystals, and on south aspects also a sun crust. The base of the snowpack is composed of weak faceted snow at alpine and treeline elevations. These basal weak layers have been producing large avalanches as recently as December 31. Human triggering any of these layers is most likely on slopes that didn't previously avalanche and on slopes that have variable snowpack depth, such as rocky alpine features.

Regions covered