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Backcountry Advisory

As of Wednesday, April 20

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Avalanche hazard: LOW increasing with daytime warming

Travel Advisory : Springtime has finally arrived in the mountains and the typical melt-freeze cycle has set in on all aspects but due north in the alpine terrain. North aspects may also deteriorate with the forecast warm overnight and daytime temperatures. The deeper weaknesses within snowpack are still lurking and recent avalanching on these layers has been observed. Avoid any steep rocky terrain where the snow cover may be shallow or where a cornice line looms above. Plan your day so that you are not traveling on slopes that have been turned to mush by the sun.

Avalanche Activity: Numerous moist sluffs have been occurring throughout the week. Sometime during the day on April 18 two deep releases occurred in Garibaldi Park. Their characteristics were similar – NW aspect, likely cornice triggered, and likely failing on one of the crust weaknesses. One of the avalanches pulled out a second deep release on a roll well down the slope near the base of the debris. On April 19 the sun triggered a likely storm snow slab on a west aspect of Decker Mountain. Could the weight of a skier/snowboarder trigger a deep release? Who knows!

Snowpack : Solar aspects and lower elevation terrain now have a surface melt-freeze crust that will moisten during the day. 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: Sunny skies and warm temperatures will dominate the week. We could see a minor disturbance on Friday but then a return to sunshine for the weekend.

Call 938-7676 for the daily avalanche bulletin or see the Whistler-Blackcomb website. Conditions around the province can be found at www.avalanche.ca

— Whistler Mtn Snow Safety

From the Duffey courtesy of MOT

Experienced pro skiers have been observed giving the big lines respect or avoiding them this week as confidence drops given the complexity of the April snowpack. The April solar power was evident by the rash of avalanche activity on southern quadrants Monday afternoon. The release layer, a weak layer of small surface hoar and facets 25 cm down at shady treeline sites, has gained some strength since then. Since this combination involves persistent grains the old storm snow will become active again (on a more isolated scale) once the surface moistens. Watch for weakening (increased ski penetration) on the shady aspects over the crusts. Beware of the triggering potential of small avalanches in motion. Will the size 1.5 that releases when I drop this chute step down and turn into a size 3 arriving at the valley bottom? Is the skiing quality of this boot-top schmoo worth the high danger?

This slab/weak layer/crust combo put a local ski tourer in hospital after a ski cut went wrong on a wind loaded north aspect and she rode out a size 2 slab avalanche through a gully and scattered trees. Her spinal fracture was likely from a collision with a hemlock.

On Monday afternoon on solar aspects storm snow slabs with crowns to 50 cm in thickness were propagated widely to size 3 over a thin crust from the first week of this month. Activity has slowed since then.

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