From Storms to Spring

Date
lundi 24 mars 2025
Auteur
Tyson Rettie and Wendy Lewis, Avalanche Forecasters
Étiqueté sous

It’s no secret that spring can offer some of the most enjoyable conditions in the mountains. Warmer and longer days make it prime time for adventures, but the season also comes with unique avalanche hazards to keep in mind.

Early spring has historically been one of the deadliest times for avalanches—likely due to a combination of rapidly changing weather, persistent weak layers, and human factors. When we add long, sunny days that can create a false sense of security into the mix, it can be a recipe for underestimating avalanche risk. 

Preparing for a wide range of conditions is key. It might feel like summer in the valley while winter lingers at higher elevations, or warm temperatures may reach the mountaintop. Understanding the avalanche forecast and mountain weather can make all the difference in keeping your spring adventures safe and enjoyable.

A large avalanche on an alpine slope

Very large avalanches on deeply buried weak layers should be expected, like this recent example from the Valemount area. Credit: Boosted Imagery

Change on the Horizon

A significant warming event will bring a serious rise in avalanche danger this week and shift us into more spring-like conditions. Freezing levels are forecast to rise towards 3000 m, impacting the South Coast on Tuesday, and seeping into the southern interior Wednesday.

Large and destructive avalanches are a major concern as persistent weak layers across many forecast regions are expected to become reactive. In shallow snowpack areas, such as the eastern Purcells and Central Rockies, weak snow at the base of the snowpack may produce full-depth avalanches.

This will be an extra layer of complexity to manage alongside our usual spring concerns. 

Weather map showing high freezing levels for most of western Canada

By Wednesday afternoon, freezing levels are forecast to reach over 3000 m in many regions. Source: Mountain Weather Forecast

Typical Spring Avalanche Hazards and Problems to Watch Out For

Wet Loose Avalanches

  • Sunshine and warm temperatures weaken the snowpack, reducing cohesion and increasing the likelihood of avalanches. 
  • Morning sun impacts east-facing slopes, shifting to south and west aspects in the afternoon, with the strongest warming near rocky outcrops. 
  • Snow that doesn’t refreeze overnight deteriorates faster as daytime temperatures rise.
  • Rain-on-snow events rapidly destabilize the snowpack.
A valley has multiple avalanche paths containing avalanche debris

A widespread avalanche cycle should be expected during the upcoming warming, like this example from the start of March. Credit: South Rockies Field Team

Persistent Slab Avalanches

  • Rapid warming can trigger buried weak layers.
  • Dormant weak layers from January and February may become active again. These layers are widespread across many forecast regions.
  • Large avalanches may run to valley bottom—often into terrain where recreationists would not expect overhead danger. 
  • The risk is especially high during the first major warm-up of the season.
A rider stands in front of a wet avalanche that has run in trees

Wet avalanches have the potential to run long distances in the spring. This example from the Fernie area is a good reminder that avalanches can run through forests and that knowing what is above you is always important. Credit: South Rockies Field Team MIN.

Cornices 

  • Sun and warm temperatures weaken these overhanging masses of snow. 
  • Cornices can break suddenly, posing a serious hazard for anyone on the ridge or the slope below.
  • Cornice falls are large loads that have the potential to trigger deeply buried weak layers, producing very large avalanches.
A ridge with a large cornice running along it

Large overhanging cornices like this near Whistler are a major concern as we head into spring. Give these a wide berth when traveling on ridges and minimize your exposure to overhead slopes with cornices, especially during periods of warming and sun. Credit: MIN User Kirill Kokorin

Storm or Wind Slabs

  • Instabilities often linger on high-elevation, north-facing slopes, where they are last to be affected by spring warming and protected from the sun.
  • Convective flurries are short-lived, localized weather events that can deliver sudden bursts of heavy snow, reduced visibility, and gusty winds. They can elevate avalanche danger by rapidly forming storm or wind slabs.
Ski tips and a pole are pictured in a point of view shot from the top of an avalanche fracture line.

Widespread storm slab avalanche activity was observed over the weekend. The recent storm snow is expected to remain unstable as the warming progresses. Credit: MIN User BARKER.DBEN.

Remember, avalanche risk isn't the only concern in spring. Warm days and cold nights drive melt-freeze cycles in the snowpack. Hard surface crusts are often present in the morning, reducing avalanche danger but making self-arrest difficult on steep slopes.

The Good News? 

With thoughtful planning and decision-making, you can still enjoy the best of spring.

  • Check your local avalanche forecast and avoid exposure to avalanche terrain during high danger.
  • Remember snowpack and avalanche problems will vary significantly with elevation.
  • Conditions can deteriorate rapidly. Be prepared to step back to simple terrain and avoid overhead hazards to minimize your exposure.
  • If traveling on exposed slopes, do so early in the day before warming and sun weakens snow surfaces and cornices.

Stay ahead of conditions by being flexible with your plans, and prioritizing safety as we enter this significant warm-up and the mixed bag of spring conditions that will surely follow.