Backcountry Advisory 

As of Wednesday, March 19

The most intense period of last week’s storm (March 12, 13) brought 120cm of new snow in a 48-hour period to the alpine regions of the mountains in the Whistler area. Winds on March 13 gusted to over 150 km/h at the peak of Whistler Mountain. The freezing level throughout the storm fluctuated between about 1,400m and 1,800m, but it finally began to drop on March 16.

When conditions improved enough to allow avalanche professionals in the Whistler and Duffey Lake corridors to get out into the field and to survey the damage, the widespread debris indicated that many paths had run naturally during the storm cycle. Subsequent explosive testing produced more results. Many of the avalanches were running only within the storm snow, while others pulled down deeper into old surface hoar, crust and facet layers.

As is the norm in our forgiving snowpack, the storm snow settled rapidly and each successive day of explosive and ski testing produced fewer and smaller avalanches.

Daily flurries associated with periods of moderate winds are keeping the surface layers active, but the cooler temperatures are making for a relatively soft slab. Depending on the snowfall intensity, the winds, and the forecast for rising freezing levels over the next few days, the surface slab will likely become enough of a hazard to push up the avalanche danger again. Last week’s storm snow should continue to stabilize, but the chance of a large, deeper release still exists and cannot be ruled out.

Cornices have grown dramatically over the week and have been calving off some sizeable chunks. These chunks are the likely triggers that could produce avalanches running on the old snow layers. Travel with caution if you are navigating through whiteout conditions, and make certain that you are not getting too close to the overhang on the ridgeline or exposing yourself to danger from above. Keep in mind as well that the flurry activity will continue to provide a loose surface layer that may become moistened and begin to sluff should the sun appear even briefly.

As of March 19, the avalanche danger is rated as MODERATE. Check for the most current conditions at avalanche.ca or 604-938-7676.

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