Remote Triggers, Wide Propagation and Why You Need to Dial It Back

Date
Friday, February 28, 2025
Author
Ryan Buhler, Forecast Program Manager
Tagged under

Wide propagation and remote triggering have us worried

We currently have a Special Public Avalanche Warning in place for most of our forecast regions in western Canada due to a tricky snowpack and challenging persistent slab problem. As we head into the weekend, the warm and sunny weather forecast is likely to exacerbate this problem. 

There has been a worrying trend with many of the avalanches we’ve seen reported over the last few days: wide propagation and remote triggers. These characteristics add an extra layer of complexity to an already difficult problem. 

a large avalanche that started in the alpine and ran into treeline

An avalanche near Kootenay Pass on Monday propagated widely across multiple features.

Wide propagation and remote triggering are both indications of a prominent weak layer in the snowpack with a cohesive slab above it. When an avalanche can propagate widely, it can run across multiple features in a slope, even if they appear somewhat disconnected. This means the avalanche can be much larger than expected and run much further than normal. 

a large avalanche that has propagated across a variety of alpine terrain features

This natural avalanche near Pemberton on Wednesday propagated 600 m wide across multiple features on the slope. 

To add to this concern, we also have plenty of reports of remote triggering, where the avalanche occurs away from the point where it’s triggered. They can be triggered from a fair distance away from the avalanche path, including from ridgelines above, on an adjacent slope, or from flat terrain below. Predicting where or when you might remotely trigger an avalanche is almost impossible.

a set of skier tracks partially covered by an avalanche

This avalanche was triggered remotely from 75 m away on low-angle terrain.

a small terrain feature with an avalanche down it

This slope near Lake Louise was remotely triggered by skiers travelling on the shoulder above it. Credit: MIN user col.j.stew

All of this means that we need to take a different approach to travelling in the mountains this weekend. Areas that normally seem safe may be dangerous, and there may be no warning signs that instability is present. The only way to manage the risk is through managing your terrain choices and practising good travel habits. 

Here are some tips:

  • Always be aware of your surroundings and watch what is above you; it is possible to trigger avalanches from the bottom of an avalanche path. 
  • Watch for other groups and give each other a wide margin of error. Remember, remote triggering is possible from a distance.
  • Avoid exposure to overhead hazards, especially during periods of strong sun and warming. 
  • Choose really good safe spots. Like really good. Persistent slabs will propagate much wider than you might expect and pull back into surprisingly low-angled terrain. Make sure you are regrouping well away from danger.
  • Maintain good communication. Radios are a useful tool within your group. Make sure everyone is on the same page. “Where are our safe spots?” “What is the escape route if an avalanche does happen?”
  • And of course, use terrain wisely…when the snowpack is the question, terrain is the answer!
  • Make your uptracks in the safest place you can. Think ridges, ribs, and forested areas.
  • Be diligent about terrain choices, and stick to slope angles less than 30 degrees when in clearings, open trees, and alpine terrain.
  • Be aware of what’s above and around you. Remote triggering is a real concern right now! Avoid terrain traps that could increase the consequences of an avalanche. 

The bottom line is that this is an avalanche problem that you really don’t want to gamble on. The consequences of an avalanche are incredibly high, and it’s just not worth the risk of sticking your neck out there. Dial it way back and reframe your goals from “shredding the sickest line we possibly can” to “having a fun day out riding with friends.” The mountains will always be there, and we want to make sure we’re there to enjoy them when they’re safer—it’s time to take your foot off the gas, slow it down, and get back to basics. 

an avalanche that has propagated across features on steep alpine terrain

This large avalanche near Whistler was remotely triggered from flat terrain over 100 m away and subsequently propagated 400 m wide across multiple features on the slope.

a person on a snowmobile looking at a small terrain feature that avalanched remotely

Remote triggering small slopes from flat terrain is a clear indication to stay away from larger slopes where the consequences would be much higher. Credit: North Rockies Field Team MIN

This avalanche near Pemberton last weekend was remotely triggered from flat terrain 150 m away. Credit: MIN user matthew.dahabieh