- Date
- Thursday, March 5, 2026
- Tagged under
March kicks off with a challenging persistent slab problem
The key message right now is that there isn’t a clear message, except for patience. 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 areas in western Canada have one or more buried weak layers in the upper snowpack. These layers are becoming less obvious as they get buried deeper, avalanche activity slows down, and triggering becomes harder. The problem then becomes what we call “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.
To avoid this, professional operations spend lots and lots of time assessing a run to see if it's safe to ride. They dig many snowpits, throw explosives, and track the history of each slope through the winter. As a recreationist, that isn’t practical. Instead, the way to stay safe is to manage the slope angle that you are exposed to, including the slope angle of slopes above you. Being patient and sticking to low-angle slopes is the best approach when managing uncertainty and a dangerous snowpack.
And when we say low-angle slopes, think less than 30 degrees in areas with Considerable danger. At High danger, avoid avalanche terrain entirely.
The life cycle of a persistent slab problem
Persistent slab problems evolve over time. Early in their life cycle they are usually shallow, reactive, and relatively predictable. Later they tend to become less predictable, harder to trigger, and more destructive.
At first, a weak layer forms near the snow surface. It may take time for enough snow to accumulate above it to create a slab. Once a slab develops, avalanches are often easy for riders to trigger. Whumpfs and shooting cracks are common and the problem is obvious. This active stage can last through multiple storms, with avalanches becoming larger as the slab thickens. During this period the problem often follows a recognizable terrain pattern, making it easier to manage by avoiding the affected slopes.
Over time, the problem starts to heal and avalanches become less likely. The weak layer may slowly gain strength and it will become harder for the stress from a person on the surface to affect it as it gets buried deeper. This is when persistent slabs become more difficult to manage. Triggers are less common, but if the layer does fail the resulting avalanche is often large and destructive. Clear warning signs become rare. Natural avalanches are uncommon, and digging down to the weak layer takes time and expertise to test and interpret. It can be difficult to determine whether the problem still exists and which terrain features remain potential trigger spots.
Some regions appear to be transitioning from the active stage toward this more uncertain healing phase, while others may still be developing into the active stage. Let’s dive into our current understanding of the problem in our forecast regions.
