Avalanche Canada is warning about a persistent slab problem. Photo by Stephen Strand
While the weather this weekend will be warm, Avalanche Canada is advising people to be careful while out enjoying the mountains.
According to Avalanche Canada, March kicked off with a challenging persistent slab problem.
“The key message right now is that there isn’t a clear message, except for patience,” Avalanche Canada stated in a release. “The snowpack is complex and different everywhere, so it’s crucial to get the forecast each day for where you intend to go, and to localize your hazard assessment by making observations, choosing conservative terrain, and being on the lookout for signs of instability.”
Many parts of western Canada have one or more buried weak layers in the upper snowpack, and these layers are becoming less obvious as they are getting buried deeper, avalanche activity slows down, and triggering becomes harder.
Avalanche Canada, though, says the problem then become what is called “low-probability/high-consequence.”
“You might be happily riding around with no cracking or whumpfing, thinking it’s all good–and then suddenly hit the sweet spot and trigger a very large avalanche,” Avalanche Canada states.
To avoid this from happening, professionals are spending lots of time assessing a run to see if it is safe to ride.
They do so by digging many snow pits, throw explosives, and track the history of each slope through the wintertime.
For those who are heading out for recreational purposes, Avalanche Canada says this isn’t practical to do.
Instead, in order to stay safe, it is advised for people to manage the slop angle that they are exposed to, which includes the slope angle of slopes directly above the person.
“Being patient and sticking to low-angle slopes is the best approach when managing uncertainty and a dangerous snowpack,” Avalanche Canada explains.
Low-angle slopes are less than 30 degrees in areas that have Considerable danger of avalanches occurring.
For areas that have a High danger of avalanches occurring, avoid avalanche terrain entirely.
These persistent slab problems evolve over time, and in the early part of their life cycle, they are usually shallow, reactive, and relatively predictable.
But, later on, they tend to become less predictable, harder to trigger, and more destructive.
Initially, a weak layer forms near the snow surface, and it could take time for enough snow to accumulate above it to create a slab.
Then, once the slab develops, avalanches are often easier to be triggered, and whumpfs and shooting cracks are common and the problem is obvious.
This active stage is able to last through multiple storms, with avalanches becoming larger as the slab becomes thicker.
It is at this time that the problem often follows a recognizable terrain pattern, which makes it easier to manage by avoiding affected slopes.
But, over time, the problem starts to heal and avalanches will become less likely, as the weak layer may slowly gain strength, which will cause it to become harder for the stress from a person on the surface to affect it as it gets buried deeper.
This is when the persistent slabs become more difficult to manage.
While triggers are less common, if the layer does fail, the resulting avalanche is often large and destructive.
On top of that, clear warning signs become rare.
Currently, the mountains west of Calgary has a Considerable risk of avalanches occurring.
That is because there is uncertainty regarding a layer of facets 40 to 60 cm deep that is reactive at the treeline and above.
Several avalanches have failed on this layer over the past week.
Also, flurries continue to add onto the snowpack.
Recently, the area received over 10 cm of snow, which is helping to improve the ski quality.
But, this improved ski quality comes with a small price, as there is now an added load.
Before heading out to the mountains, click here to stay up to date on avalanche conditions.
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