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Backcountry Advisory

As of April 27

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Alpine/ Treeline/ Below Treeline: LOW in the morning, increasing to CONSIDERABLE with exposure to the sun.

Travel Advisory: We have not received any new snowfall since April 18. Sunny and warm conditions have prevailed since then, and all aspects have gone into the typical springtime melt-freeze cycle. Cornices grew during the last storm cycle and they are starting to calve off. Of particular concern are two deeply buried crusts and associated weak layers. Warm temperatures combined with the solar effect will not only result in the usual springtime surface instabilities, but will also have the potential to trigger deep slab releases in some isolated areas. Natural cornice fall could also be a sufficient trigger.

Give any large slide paths and heavily corniced ridgelines a wide berth, as the weaknesses in the snowpack have proven very difficult to predict. Solar aspects will sluff when the weak surface crust breaks down.

Avalanche Activity: Widespread solar-induced avalanche activity has occurred throughout the past 10 days. The avalanches have been a mix of loose wet surface instabilities, slab avalanches involving the storm snow layers, and deep slab avalanches going down to buried crust and facet weaknesses that formed earlier in the season. The activity has slowed down but we are still seeing recent natural slab releases that appear to have run in the storm snow and also on the deeper crust weaknesses.

Snowpack: All aspects now have a surface melt-freeze crust that will moisten at various times during the day as the sun swings through the sky. The crust varies in strength and thickness depending on aspect, elevation and overnight recovery. The early March crust is buried anywhere from 80-150 cm down, while the late January crust can be found up to another 30 to 80 cm deeper within the snowpack.

Weather: Temperatures are expected to cool by midweek and we could see more cloud and possibly some flurries by the weekend. The cooling will result in a stronger overnight crust recovery and possibly some good corn conditions. Call 604-938-7676 for the current Whistler-Blackcomb avalanche bulletin or see the CAA site at www.avalanche.ca

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