Three Main Factors Of Avalanche Risk

Weather

Avalanche danger is affected by changing weather. Very often, avalanches happen right after a large snowfall and the degree of danger will gradually diminish in the days to follow. This means that whilst we skiers are the happiest after a big dump of fresh snow, these conditions are also often very dangerous. The wind also plays a roll in avalanche creation. Heavy winds transport snow into large packs that are often unstable and susceptible to slides. As the temperatures change the consistency of the snow layers is also affected. Sudden mild and rainy conditions weaken the snowpack due to the presence of liquid water. As the water infiltrates the snowpack it can trigger rather spontaneous avalanches. On the other hand, a longer cold period can change the snow crystals and build icy layers that have a lower density. These conditions lead to development of persistent weak layers in the snow pack, which act as gliding layers for later snowfall. Persistent weak layers can lead to large avalanches and high levels of danger for an extended period of time.

Terrain

Both the terrain shape and terrain angle (gradient) affect avalanche risk. Simply put; avalanche terrain is steep enough for the snow to slide! The steeper the slope, the more gravitational pull. Everything in nature is unstable above 30 degrees, however the stability of snow is also dependent on the other conditions. In certain conditions snow is unstable at 25 degrees, while in others in can remain stable above 40. The best way to calculate slope angles is through the use of an inclinometer.

Snow Layers

Most skier involved avalanches are triggered by the skiers themselves! Very often a persistent weak snow layer in the snow pack is to blame. Persistent weak layers can produce avalanches for days, weeks or even months, making them especially dangerous and tricky to maneuver. The best way to address this danger is to dig a snow profile and understand the characteristics of the snow pack. I will write a blog post shortly on how to analyze a snow profile.