Spring Ski Season is great for touring, backcountry and off piste skiing and snowboarding to traverse higher and also deeper into the backcountry. This time of year brings a lot of spring avalanches, Make sure your carrying your Avalanche Safety Kit.
Spring avalanches occur due to both snowpack and ambient air temperatures. When the air around you increases in temperature, so too will the snowpack’s temperature and the surface layers begin to melt. The result of all that is the snowpack weakens and gets heavier, causing more tension because the surface layers are wetter.
Also continually changing warm and cold temperatures.
So the snow is frozen overnight and then starts to warm up and thaw during the day making it less stable
Wind can turn safe snow into dangerous snow very quickly.
It does so because it erodes snow from the upwind side of obstacles like ridges and deposits them onto downwind terrain.
The wind is capable of depositing up to ten times more snow on the ground than snow falling from the sky. As such, it’s one of the most common denominators in spring avalanche accidents.
As you’ll have gathered by now, wind can add a considerable amount of weight onto existing snow. Plus, it can quickly form a slab that can cause a fracture.
Sun radiation affects snow temperature, which plays a pivotal role in deciding the snow’s intensity. Sun-exposed slopes present a higher risk of avalanches during drier spring weather, resulting in rapid warming and melting due to snow weakening.
Warmer weather doesn’t always spell bad news out on the slopes as it allows for greater bonding of individual snowpack layers.
It only becomes a problem when the sun’s influence on the snow temperature results in rapid warming and melting.
Atmospheric humidity is the amount of water vapor that gets held in the air. We can measure it as water vapor pressure, the mixing ratio, or even specific humidity (the ratio of water vapor mass against total air mass).
In humid conditions, surface hoar (frost) can form on top of the snow in above-freezing temperatures. Surface hoar itself isn’t dangerous and is quite fun to ski on, but when snow falls on top of it, the risk of avalanches occurring increases because it becomes a sliding surface that can sometimes take months to stabilize.
While there are several red flags that can help people determine the likelihood of an avalanche, some of them relate to timing.
For example, evidence of recent avalanches on the slopes is a sure sign of instability. In general, if you can see recent avalanche activity, that means the snowpack is no longer stable.
Time of day
There’s also the time of day to consider when attempting to predict the likelihood of avalanches. During daylight hours, avalanches are prevalent due to air temperatures getting warmer. But, they are less likely to occur in the evening or early in the morning. That’s because of a lack of radiation from the sun.
Any new snow that has fallen in the past 24 hours will not have had time to bond with existing snow surfaces, and so will be inherently unstable. The problem is a lot of skiers are keen to create new tracks in the fresh snow, triggering a plethora of new avalanches.
New snow, alongside wind, can potentially be a lethal combination and creates ideal conditions for wind loading and instability. Some skiers may take to the slopes with an avalanche airbag to help them stay as high up as possible in the snowpack should the worst happen.
If you ever spot rollerballs and pinballs out on the slopes, you are likely witnessing the beginning of a loose wet avalanche.
Such avalanches form due to new snow or old existing surface snow that is melting. When the water content increases in the snow, it becomes unconsolidated – in other words, the snow begins to separate.
The result is that rollerballs and pinballs begin to form, and you start to see a fan-shape down the slopes as they progress downward.
Rollerballs and pinballs don’t usually travel fast, but because they increase in mass when they roll downhill, they can do significant damage.
As soon as the snow hits the ground, a process known as metamorphism occurs and is the only natural substance where solid, liquid, and vapor phases all co-exist simultaneously.
In a nutshell, melt-free metamorphism is the process of repeated snowpack melting and freezing cycles.
You’ll see examples of melt-free metamorphism in action when you come across wet snow in spring. And you’ll usually find evidence of it either on the snow’s surface or buried underneath other recent layers of snow. While melt-free metamorphism is an interesting scientific concept to witness, it’s also one of the leading causes of spring avalanches.
Cloud cover greatly affects how much radiational cooling occurs at night. If there is any cloud cover at night, it can potentially inhibit the cooling of the snowpack. Plus, it can enable melted snow and associated weakened snowpacks to progress deeper in the snow cover. Such conditions typically lead to loose slide action and wet slab avalanches.
Last but not least, if you ever witness cracking or blocking of the snowpack, it is evidence of severe instability. Such unstable snow slabs should get avoided, especially when encountered by steep slopes.
The cause of such unstable snow slabs is due to wind slab – a cohesive layer of snow deposited by the wind to downward terrain. Be sure to carry a transceiver with you at all times on the slopes in case you ever fall afoul of unstable snow slabs and need rescuing!
It’s important to stay safe and have the correct training when skiing or snowboarding off-piste please check out further blogs below:
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