To assess the avalanche risk in off-piste skiing, first take the “Bulletin du Risque d'Avalanches” (BRA) by massif from Météo France.
Find out about the conditions from the National Agency for the Study of Snow and Avalanches ANENA, created following the UCPA avalanche in Val-d'Isère in 1970.
Then, if you ski in a resort, observe the level of risk for the day assessed by the slopes patrol services of the ski areas:
• Yellow Flag = low to limited risk
• Yellow and black checkered flag = marked risk to high
• Black flag = generalized risk (the stations then closed)
Then, on arrival on the ground, from the first minutes of the day, observe the recent avalanches, note their altitude, their orientation, and their location (near the ridges, mid-slope, etc.). This will allow you to transpose these factors to the slopes you want to take.
Also note whether the observed fresh avalanches were triggered intentionally by the slopes patrol (Intervention Plan for the Triggering of Avalanches, or PIDA), by skiers, or spontaneously outside the ski areas. Spontaneous avalanches should alert even more particularly to the instability of the snowpack.
Take into account recent aggravating factors:
• Snowfall
• Snow displacement by the wind (= snowfall)
• Warming
• Rain
• Long periods of good weather and clear nights, mainly from November to early March
Pay attention to this last factor, it is extremely dangerous and almost unpredictable.
A sequence of clear nights induces a cycle of cold in the snowpack, caused by a strong radiation of terrestrial heat towards space, particularly in the north faces, which in the heart of winter, never see the sun.
This results in strong temperature gradients (difference between 0 ° on the ground and temperature in the snowpack, relative to the thickness of the latter). And the deep to intermediate layers, stabilized beforehand, transform into grains with a flat face, (also called deep frost or goblets), which have no cohesion and transform the snowpack into a castle of cards, or into a ball bearing. And the less the snow depth, the higher the gradient, so the faster and more important this transformation. This phenomenon is 100% invisible without digging to the ground.
This metamorphosis of the snow crystal, called "constructive metamorphosis", is final, until melting. Skiers must therefore be particularly wary of seasons which started out with little snow and good weather, the sleeping trap is then buried until spring.
A structure like PowderWeGo ski school can organize private evening briefings to help you understand more about the snow metamorphosis phenomena.
More generally, be particularly wary of the North faces, which remain dangerous longer than the East, West and South faces, and which can become dangerous again after stabilization, due to the phenomenon mentioned above.
In off-piste skiing,
• Always be equipped with Avalanche Victim Detectors (DVA), and train in their use regularly (essential).
• Always be equipped with shovels and probes
• Always be equipped with ABS® airbags
• Always have several means of communication and know the emergency number (112). Have a GPS to be able to give your coordinates to the emergency services, and an altimeter to give them your altitude (essential to be found).
• In general, ski accompanied, preferably by a specialist off-piste ski instructor, or failing that by a mountain guide, who is not an instructor, but is familiar with the routes and the snow.
You can get closer to these two structures, based in Val-d'Isère and specializing in off-piste skiing, and organize off-piste skiing trips in the most beautiful spots in the world:
PowderWeGo, off-piste ski school in Val-d'Isère and organizer of off-piste ski trips.
TopSki, off-piste ski school in Val-d'Isère since 1976.
Off-piste skiing involves risks, including avalanches. Ski accompanied by a professional.
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