Tricky snowpack structure returns to the coast

Whumpfs and remotely triggered avalanches have returned to the Sea to Sky forecast region, and areas in the South Coast Inland like the Duffey Road and Coquihalla. These recent avalanches mean there’s potential to trigger slides accidentally from a distance, including “toe triggering” or releasing the slope above you from a spot you wouldn’t normally consider steep or risky.

Thanks to Evan Stevens ( for this photo from the Blackcomb backcountry on Wednesday.

This photo taken in the Brandywine area Thursday.

We use past avalanches to forecast future ones. And several similar avalanches suggest we have a trend, not just a weird one-of-a-kind to gawk at and forget. Here’s a sketch of the snowpack structure to help picture the problem.

Here are some more examples of MIN reports from the past week highlighting whumpfing and avalanche activity suspected to be running on the same buried weak layer. Here, here and here.

This kind of layering doesn’t just heal and disappear in hours or days. It’s likely to remain for days to weeks. Plan on it being problematic at least through the weekend as Evan Stevens pointed out in his recent South Coast Touring Group post. Similar conditions about one month ago caught several people off guard.

There is some uncertainty for how this layer will react in the coming days. A higher level of uncertainty should affect how we manage the problem. If you’re looking for a little neighbourly advice, here are some ideas:

  • Pull in the reins. Adopt a conservative approach to choosing terrain. Be disciplined about maintaining that approach.
  • Avoid steep, convex, unsupported slopes at treeline and in the lower alpine.
  • Stay away from thin/variable depth/rocky avalanche terrain.
  • When the sun comes out after a cool period, loose snow sluffs out of steep terrain and cornices can begin to fall. Small avalanches and cornice falls add significant weight to the slopes below and increase the chance of triggering buried weak layers. Take stock of what is above you and minimize your exposure when the sun is out.

Written by: Ilya Storm