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Backcountry Avalanche Advisory

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As of Wednesday, March 4
Avalanche hazard rating
Alpine: Moderate through Friday
Treeline: Moderate through Friday
Below Treeline: Moderate through Friday

The avalanche danger may increase on any slopes with exposure to the sun.

Travel Advisory: We received over 30 cm of new snow on Sunday and Monday accompanied by strong South and Southeast winds gusting at times to 110 km/h, switching to the Southwest at the tail end of the storm cycle. Freezing levels rose to 1,900 metres then fell to the valley bottom after the passage of the storm.

Avalanche Activity: Avalanche control conducted periodically during the storm cycle produced up to size 2.5 soft slab avalanches within the storm snow layers. It was apparent that at higher, more wind-exposed elevations there was a very stiff slab that softened up on descent. Some previously shallow rocky and faceted areas appear to have had activity stepping down to the buried facets. Widespread natural avalanche activity occurred in the alpine during the storm cycle on the various wind-loaded aspects, with wet snow avalanche running below treeline in many steep gullies and drainages. Cornices have grown large and could be a potential trigger for a deeper release.

Snowpack: Diurnal cooling has helped to tighten in the easy shears that were observed within the new snow layers during the storm. However, you can expect some isolated areas to remain reactive to a skier trigger. As much as 250cm of snow is now sitting over a variety of old surfaces which includes surface hoar, hard windslab, facets and depth hoar. There was also a strong melt-freeze crust on sun exposed slopes that will make a good sliding layer below the storm snow. The crust/facet combination that formed in early December is in some areas buried below a stiff hard bridging layer. In other areas where the snowpack is shallower, the basal weakness is more extensive and the overlying bridge is much weaker. These persistent weak layers appear to be reaching their critical threshold in some isolated areas with reports of skier-triggered activity with significant destructive potential occurring yesterday in the Spearhead Range as well as in the Mount Currie region. If you experience any large settlements or "whumphing" during your travels, this should be a red flag worthy of your attention. New surface instabilities may rapidly form today with the combined effects of the sun and warming.

Weather: Another weak system is expected to bring scattered flurries to our region later today, then clearing again later on Thursday and Friday. Freezing levels should rise to around 1,300 metres today, then drop to closer to the valley bottom for the duration of the week. A more organized system may arrive on Saturday.

Conditions may vary and can change rapidly. Check for the most current conditions before heading out into the backcountry. Daily updates for the areas adjacent to Whistler/Blackcomb are available at 604-938-7676, or surf to www.whistler-blackcomb.com/weather where there is also a link to the CAA public avalanche bulletin, or call 1-800-667-1105

- Whistler Mtn Snow Safety

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