Avalanche forecast

Purcells

Nov 23 – 24, 2012Avalanche Canada
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Archived · expired 14 years ago

Avalanche danger

Sun
Mon
Alpine
No rating
Treeline
No rating
Below
No rating
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Highlights

This bulletin is based on limited data. Local variations in conditions are likely to exist. Check out the forecaster blog for further details on interpreting early season bulletins.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–5
    Moderate SW winds have redistributed recent storm snow and has formed touchy wind slabs. Wind slabs exist on open leeward slopes and behind terrain features. New storm snow is adding weight to recent storm storm slabs, and hiding wind slabs.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–6
    Two persistent layers exist through the region. A surface hoar layer buried 40-80cm down, and an early Nov crust buried near the base of the snowpack. The weight of a skier, or sledder hitting the sweet spot could trigger these slabs.

Confidence

Poor - Due to limited field observations for the entire period

Weather Forecast

A Pacific frontal system is moving through the interior regions Friday and extending into Saturday. This will bring strong ridgetop winds and moderate amounts of snow, especially in upslope areas. After the front passes, a weak ridge of high pressure will push into the region bringing dryer, cooler, and clearing conditions that will last through the weekend. Freezing levels will stay in the valley bottom through the period.

Avalanche Summary

Several size 1.0 natural avalanches were reported near the central part of the region on North aspects @ 2300m. Control work in the Dogtooth Range produced Size 2-2.5, on NE through SE aspects above 2100 m. The failure plane being the Nov 17th surface hoar layer. This layer is a concern of mine heading into the weekend, it may be easily triggered by the load of a sled, or skiers hitting the sweat spot and initiating a large avalanche.

Snowpack Summary

Storm slabs and wind slabs are reported to be widespread at treeline and in the alpine. Most suspect slopes that host touchy wind slabs are leeward (North-North East) and behind ridge crests and terrain features. A couple early season persistent layers also exist. The most reactive being a surface hoar layer that was buried on November 17th. This is buried down 40-80 cm and may be easily triggered under he weight of skier or sledder. The early November crust also exists deeper in the snowpack has been reported as widespread at all elevations and on all aspects. Below this crust large faceted crystals are forming. Alpine snow depths are 150-200cm, and treeline is roughly sitting around 50-100 cm in depth.

Regions covered