No one was injured in any of three skier-triggered avalanches last weekend, but that was due to good fortune rather than good judgment.
A series of spring storms brought over 70 cm of new snow to the upper alpine in just a couple of days last week, along with high winds that elevated the avalanche risk to considerable. The three avalanches, one of which was within ski area boundaries, were rated as class two or higher on a scale of one to five.
The first slide, reported on Saturday, April 15, was set off in a permanently closed area above West Bowl on Whistler Mountain. Skiers reportedly ignored the rope and headed into the closed area, where they started an avalanche that went down a chute into an open area, where a 10-year-old skier was caught in the debris. He lost his skis, but was not injured.
The skiers who triggered the avalanche did not come to the aid of the young skier, and left the scene before speaking to ski patrol.
Ski patrol had performed avalanche control earlier that morning, before the alpine area was opened at 10:15 a.m. The slide was triggered at approximately 1:30 p.m.
According to Whistler-Blackcomb avalanche forecaster Anton Horvath, the slide area did receive avalanche control, but patrollers could not make any follow-up tests.
"One of the challenges with permanently closed areas is access. In most areas ski patrol will follow up avalanche control by doing some ski cutting in the area, which gets anything that the bombs might not have triggered," he said.
"But there are areas that are permanently closed and for a good reason, which is usually that if you fall you can land in a pile of rocks and possibly die. For that reason its not physically safe for patrollers to go into those areas to do a ski cut or slope test."
Horvath says the pocket of snow that was triggered would not have slid on its own without a skier "hitting the sweet spot."
He added that it was impossible for the skiers who triggered Saturdays avalanche not to know they were in a permanently closed area.
According to patrol, they use an average of 130 kilograms of explosives during avalanche control before opening the mountain, but snow pockets can remain after work has been done. As a result ski patrol is reminding people to observe all permanent closures or other closures marked on the mountains. Anyone caught in a permanently closed area will immediately lose their pass.
The second avalanche took place on Sunday at approximately 2 p.m., about one kilometre outside of the Blackcomb ski area boundary in an area accessible from the top of the Blackcomb Glacier. It was also rated as a class two, sliding approximately 250 metres.
According to Horvath the crown of the avalanche was about 150 cm deep, and carried the skier who triggered it a long way down the slope. The skier took off after the accident.
As a precaution ski patrol responded with a dog and rescue team to search the area, and confirmed that nobody was buried in the slide.
The area in question does not receive any regular avalanche control because there is very little risk that an avalanche could move in-bounds.
The third avalanche took place on Monday, and was also triggered by a skier. That slide was reported in the Fissile area, outside the Whistler ski area boundary, in an area called Banana Chute.
The crown of that slide was about 75 cm deep, and once again the skier was caught in the debris but managed to ski to safety. It is estimated that it was about a 2.5, which is considerably bigger than the 2.0 avalanches.
Horvath said Tuesday the conditions in the backcountry are unpredictable.
"There was a really variable bond between the storm snow and the melt-freeze crust formed by (the previous weeks) warm weather," he said.
"There are areas where we have more than 65 centimetres of snow loading on top of the crust and there is a very variable bond, very unpredictable at that depth. There were a number of slides triggered with avalanche control, and continued reports from the backcountry as recently as yesterday."
Whistler is not the only resort to experience an in-bounds avalanche this week. Mammoth Mountain in California had a serious slide at 2 p.m. on Monday that caught several people and buried one woman entirely. She was quickly rescued and no injuries were reported after about 200 patrollers and volunteers combed the snow for several hours searching for other possible victims.
As a result of the slide, which was estimated to be about 700 metres wide on the Climax run, the resort made the decision to close operation for the rest of the day.
Daily avalanche bulletins for the Whistler region are posted online at