Two skiers involved a large slab avalanche in behind Marmot Basin ski resort March 14 were shaken but unhurt after being dragged some 50 m through snow and rocks.
The local skiers were skinning up the Whistler Creek drainage from Marmot Basin’s parking lots when their position at the top of a rocky ridge triggered a fracture in the snowpack. The fracture propagated towards the main draw of the slope, resulting in a size 2.5 avalanche. When it stopped, the debris field was approximately 200 m long and 80 m across.
“They were lucky,” said Parks Canada public safety specialist, Steve Blagbrough. “The avalanche danger is still present.”
On Saturday, March 15, Blagbrough and colleagues from Parks Canada and Marmot Basin’s avalanche safety team hiked up and over the peak at Marmot Basin to investigate the avalanche. There they found a 120 cm crown wall, 2.5 m of debris and evidence that the snowpack has not only one weak layer, but two.
“That’s not unheard of in the Rockies, but it is unusual,” Blagbrough said.
The skiers had reached a high, rocky ridge when they felt the snowpack change. Moments later they were tumbling through the shallow snow on the far side of the avalanche. One skier lost a ski and both ski poles; the other lost both his poles; they managed to walk out on their own. Marmot Basin staff said had they been involved in the middle of the slide, it's likely they wouldn't have been so lucky.
The accident highlights what Parks Canada avalanche experts have been saying all winter: a weak layer buried deep in the snowpack means there is a risk of large avalanches on cross-loaded slopes.
“It’s one of those layers you can easily forget about,” said Parks Canada public safety specialist, Steve Blagbrough. “But the consequences of a trigger are still great.”
Blagbrough said the slope had been skied a few days previous, demonstrating how quickly a slope can go from stable to unstable.
“It's a good example of how rapidly things can change,” he said. “On this occasion it was from a significant wind event redistributing all that good skiing snow onto lee aspects and cross wind-loaded features.”
Parks Canada emphasized patience while accessing backcountry lines.
“That line you want to ride might not be in condition this weekend, next weekend or this month,” Blagbrough said. “It might not even be stable enough this year. But it's not going to go away. The mountains never do.”
Parks Canada’s daily avalanche bulletin—which showed a considerable avalanche danger at treeline on Friday, March 14—is available at avalanche.pc.gc.ca