Avalanche forecast

Purcells

Jan 4, 2019Avalanche Canada
View on map
Archived · expired 8 years ago

Avalanche danger

Sat
Sun
Alpine
4 · High
Treeline
4 · High
Below
4 · High
Open full map

Highlights

The region will continue to see substantial snowfall amounts into Friday, which is rapidly loading buried weak layers. Travel in avalanche terrain is not recommended.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1.5–3
    Expect to find reactive storm slabs at all elevations due to recent storm snow, strong winds, and mild air temperatures. Triggered slabs could step down to deeper weak layers.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    2–3.5
    The likelihood of triggering deeply buried weak layers is increasing with the recent snowfall and warm air temperature. Should an avalanche occur, it could run full-path and well into the valleys.

Confidence

High -

Weather Forecast

THURSDAY NIGHT: Cloudy with snowfall, accumulation 10 to 20 cm, moderate to strong southwest winds, alpine temperature -4 C, freezing level 1400 m.FRIDAY: Cloudy with snowfall, accumulation 5 to 10 cm, moderate to strong southwest winds, alpine temperature -3 C, freezing level 1500 m.SATURDAY: Mix of sun and cloud, light southwest winds, alpine temperature -4 C, freezing level 1000 m.SUNDAY: Cloudy with light snowfall, accumulation 5 to 10 cm, light to moderate southwest winds, alpine temperature -3 C, freezing level 1000 m.

Avalanche Summary

Storm slabs were reactive to skier traffic and explosives on Thursday, producing large (size 2) avalanches with depths around 20 to 40 cm.  It is possible that a natural avalanche cycle will occur as the storm continues Thursday night and into Friday. Avalanches could run fast and far, well into runout zones.

Snowpack Summary

A strong storm is dumping snow in the region Thursday into Friday. Around 20 to 40 cm of snow has fallen over most of the region up to Thursday evening (almost 70 cm in the far north!), and another 20 to 30 cm is expected Thursday night into Friday. All this snow has likely formed touchy storm slabs. The snow is falling with strong westerly winds, so expect deeper deposits in lee terrain features near ridges.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. Another similar weak layer is buried around 120 to 150 cm deep. The base of the snowpack has weak faceted layers 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