Early spring?
It’s amazing how fast conditions on the coast can change when February arrives. Days are rapidly getting longer and when the sun pokes out, which it most certainly will this weekend, it can feel downright tropical.
When the snowpack structure is strong, the main concern under this type of weather is for wet, loose avalanches in steep, sun- exposed terrain. As surface crusts break down, this potential increases. When the crust is strong, conditions are generally safe from an avalanche perspective.
The dance between crust recovery and daytime warming will definitely apply this weekend. Unfortunately, the snowpack in the Sea to Sky has a bit more going on under the surface. A complex persistent weak layer that has recently been responsible for several serious avalanche accidents and even a fatality is very much still in the picture. This layer is buried about 70 centimetres deep and exists in a lot of areas, but it has proven especially reactive to human triggering around the treeline elevation band.
Warming will have a complex effect on this problem. Initially, it will most certainly increase the chances of avalanches occurring at this layer. As time goes on and warming continues, the trend gets more uncertain. Will a strong surface crust prevent people or machines on the surface from triggering it? The answer to this question could change from hour to hour this weekend. Could a natural cornice fall or large, wet, loose avalanche provide the necessary trigger? The prudent answer would be “yes.”
Since this layer doesn’t exist in a uniform fashion over the region’s terrain, there is the added complexity that you may not receive negative feedback for being in the wrong piece of terrain. Extrapolate that observation carelessly and you could easily push your luck too far.
All in all, this will be a great weekend to soak up some rays and treat treeline terrain with extreme caution. Remember that sometimes there’s more going on below the surface than it might seem.
