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Touchy snowpack makes for tricky avalanche conditions

“Some kinds of avalanche problems can be here for a few days and they go away, or last a few weeks and then they go away, but these kinds of problems, which we call a deep persistent slab, it doesn’t go away, so that’s kind of the set up we have this winter.”
A size 3 avalanche was remotely triggered on March 5 on Mount Fairview above Lake Louise by skiers who stopped about 25 meters above the fracture line while the avalanche ran over the cliffs below. PARKS CANADA PHOTO

BANFF – Tricky avalanche conditions associated with a dangerous snowpack throughout the region will continue into spring.

Parks Canada public safety experts say touchy avalanche conditions this winter are associated with a deep persistent slab, due to a dry start to winter in November and December combined with rainfall in late November that created an ice crust.

“It kind of just lurks there beneath the snowpack all winter,” said Grant Statham, a visitor safety specialist for Banff, Yoho and Kootenay national parks.

The snowfall earlier this week dumped anywhere from 20 to 30 centimetres throughout various parts of the region, leading to several large natural slides throughout Banff National Park and neighbouring Kananaskis Country this week.

On Tuesday (March 14), a size 3 avalanche slid on Mount Kidd in Kananaskis Country, running over top of two popular early season ice climbs – Cryogenics and Le Lotus Bleu. While unconfirmed, Kananaskis Mountain Rescue suspects the slide may have been triggered by a skier.

On the same day in neighbouring Banff National Park, a natural size 3 avalanche was observed on the southeast slopes above the normal ski lines on Watermelon/Puzzle Peak north of Lake Louise. About 650 metres wide and up to 1.8 metres deep, it was likely cornice-triggered at the end of the storm.

Statham said other large slides were spotted on Wednesday (March 15), including up to size 3 on Pilot Mountain west of Banff and several on Mount Rundle, including a large one above the Sacre Bleu ice-climb on Mount Rundle.

“It’s pretty tricky right now. We’ve seen lots of avalanches in the last 48 hours – big ones,” he said.

“These are just what we’ve observed. We only see a small part of the big picture.”

Avalanches are classified by destructive potential.

A size 3 avalanche could bury and destroy a car, damage a truck, destroy a small building, or break a few trees, while size 4 could destroy a railway car, large truck, several buildings, or a forest area up to four hectares.

Statham said November and December are critical times for how the winter avalanche season will shape up because it forms the foundation of the snowpack, which this year saw a dry start with not a lot of snowfall.

“When it is shallow and cold like we have here, often we get really weak faceted snow forming on the bottom of the snowpack, and then it starts to get buried as the season comes along, and we get to mid-December and into January that foundation is now buried and that doesn’t heal very well,” he said.

“Some kinds of avalanche problems can be here for a few days and they go away, or last a few weeks and then they go away, but these kinds of problems, which we call a deep persistent slab, it doesn’t go away, so that’s kind of the set up we have this winter.”

Contributing to this problem is rain that fell in late November created an ice crust on the surface, and as that crust gets buried, Statham said that leads to a further deteriorating snowpack.

“The official term is faceting, but I like to say that crust rots over time, and becomes weaker and weaker,” he said.

“We’re still in that situation where we have a deep persistent slab in the snowpack.”

While this deep persistent slab in the snowpack is not uncommon for Banff and Lake Louise, experts say it is more like a one in 10-year problem in the interior and coastal mountain ranges in neighbouring British Columbia, where the avalanche death toll has risen to 12 so far this winter.

“It’s not that unique for us to be perfectly honest, but places like Rogers Pass and the Selkirk Ranges and around Revelstoke, even all the way out to the coast range, have been seeing periods of large avalanches this winter, size 4 avalanches running,” said Statham.

“It’s an exceptional avalanche year in the interior and coastal British Columbia, and here in our zone it’s also not great conditions, but it’s kind of like it is almost every year here.”

A deep persistent slab was remotely triggered on March 5 on Mount Fairview above Lake Louise by skiers who stopped about 25 metres above the fracture line, while the avalanche ran over a series of cliffs below.

Remote triggered avalanches, which are a strong sign of an unstable snowpack, are slides that occur away from the point where they are triggered. The massive slide path is visible from the Trans-Canada Highway.

“I am sure it would have killed them if they'd been caught,” said Statham.

 “You can see their ski tracks, you can see where they skied down, and then you see where they've stopped, and then you see these crazy traverses just trying to get out of the way.”

The heightened hazards following the snowfall earlier this week will ease a little with each passing day, but with the consistent deep persistent slab problem, Statham said “those problems are going to wake up” as soon as it snows again.

“That’s the thing about a deep persistent problem. It wakes up and causes large avalanches and then it kind of goes to sleep and you can easily be lulled into thinking that things are better because you might not be seeing any new avalanches,” he said.

“You can a look around and you might not see very many avalanches and you might think conditions are getting better or conditions are improving, and all it takes is either going into the wrong place or one snowfall or else the sun comes out and the temperature goes up and, boom, we see large avalanches.”

The park rescue team has not had to respond to avalanche call-outs in the park this year, however, were called on Dec. 31 when a skier triggered a size 2 avalanche near Emerald Lake in Yoho National Park, carrying him about 40 metres into the trees and causing life-threatening injuries.

While the 12 avalanche fatalities outside the parks in B.C. are above the 10-year average, Parks Canada is hoping the ongoing education in this region is getting the avalanche messages across to residents and visitors.

“I am not seeing a lot of people skiing big crazy things here, which is quite inspiring,” said Statham.

“I think people are listening closely to the avalanche bulletins and the media reports. I’ve seen lots of chatter on the ice climbing Facebook groups, on the ski touring groups, of people reminding each other about what kind of winter it is and to just be careful. I think all that outreach is working.”

Backcountry enthusiasts are encouraged to check avalanche bulletins and Avalanche Canada’s Mountain Information Network, or MIN as it is known.
MIN is for getting and sharing real-time, location-specific information. Quick reports share general snow, weather, and ice conditions.

Statham said MIN is becoming quite well used these days.

“A lot of people are sharing stories about avalanches that they trigger, which is great,” he said.

“We want people to do that. We don’t want people to be ashamed to share their stories because everybody makes mistakes. We want people to share it so others can learn and MIN is the way to do it.”

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