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Backcountry Advisory

As of Wednesday, April 19



Treeline: LOW trending CONSIDERABLE

Below Treeline: LOW trending Moderate

Travel Advisory: We received approximately 65 cm of snow since April 12 th accompanied by moderate to strong winds from the SE through to the SW. Some exposed areas are scoured down to last weeks melt-freeze crust, while elsewhere you will find deep pockets of wind transported snow. Many new features have developed, and cornices have grown. The avalanche danger will rapidly increase as the approaching storm deposits a new load of snow accompanied by moderate to strong winds. A big concern at this time of year is that with any appearance of the sun or with daytime warming, the snow quality will change rapidly. Winter-like snow will rapidly stiffen, form a slab, and become suddenly very reactive. As it continues to moisten, the surface will begin to sluff naturally particularly in steep rocky areas. Pay close attention to the conditions – don’t presume that any slope will maintain the same snow quality for a second run. Once the sun appears after the passage of this storm, stay on the more mellow terrain until the melt-freeze process once again becomes established.

Avalanche Activity: Explosive and ski testing after the passage of last weekend’s storm produced some small soft slab avalanches that were running within the storm snow layers, as well as several stiffer slabs that ran down through the full depth of storm snow to the melt freeze crust, or just above it. Crown lines varied from 30 to 80 cm in depth. It seemed as though most of the larger avalanches occurred in start zones where there had been more wind transport and the slab was stiffer. Surface roughness prior the arrival of the storm appeared to influence the bond of the storm snow to the crust. Two skier- and snowboarder-triggered avalanches in the Whistler region occurred on Sunday late in the day, and a third on Monday. All were on North facing aspects with crown lines of 100 cm in depth and more in places, running either on or just above the aforementioned temperature-affected surface. Some of the slabs were not easily triggered in the thicker part, but more easily triggered where the slab tapered off in thickness then pulling out the meat of the slab as well. This failure plane may prove to be a persistent weakness with future loading in some isolated areas.

Snowpack: The snow distribution is variable due to the strong winds that prevailed throughout the last storm cycle. The condition of the underlying melt-freeze crust is also extremely variable – in some spots it had been roughened by solar-induced sluffing and snowballing, or old ski tracks, while in other spots it is smooth. This variable likely has an effect on how well the storm snow has bonded to the underlying crust. Sunday night’s 10 cm snowfall was light density and relatively unconsolidated, forming a soft slab only in the higher, more wind-exposed alpine start zones. Below treeline the snowpack was trending isothermal before this latest blast of winter kicked in.

Weather: The system that arrived in our area this morning is forecast to stall over the coast for a few days bringing moderate accumulations of new snow, tapering to flurries on Friday morning. Fair weather is forecast for the weekend.

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 at

Whistler Mtn. Snow

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