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Avalanches can occur on almost any slope, although most commonly on slopes with an angle of between 30 and 45 degrees. Unfortunately for skiers, thats also the most common slope angle that most of us enjoy skiing down! Avalanche awareness and in particular, avalanche avoidance is something that should be at the forefront of the ski tourer’s mind both during, but perhaps more importantly, before heading out on the tour.
Many skiers are aware of the ‘Rutchblock Test’ for testing snow stability, but even before you first get your skins on, it is possible to have a good idea of the local avalanche risk. There are various sources of information that you should be checking, prior to your tour to allow you to get an idea of current snow conditions. These should be monitored on the days, and even weeks, leading up to the start of your trip. Local weather forecasts will give you an indication of how much snow has been falling in your chosen area, which direction the wind has been blowing from and what range of temperatures have predominated. This information, with practice, can allow you to build up a picture of what areas and slopes are likely to be most prone to avalanche risk when you set out.
Dedicated avalanche forecasts are available in many ski areas, and can give further info to back up your own observations from the weather forecast. They also often give specific observations from local sites which can help. There is a numerical International Avalanche Scale, which runs from 1 to 5. It is important to note that although the scale runs from 1to 5, a category “3” is not middle ground in terms of the likelihood of an avalanche occurring. The grades are always accompanied by text that warm of specific dangers. Category 1 (low), Category 2 (moderate), Category 1 (considerable), Category 1 (high), Category 1 (very high).
Having monitored the weather, both past and present, there are still observations and assessments to be made regarding where you are going to ski. Again, some of this judgement and decision making can be made from the comfort of your armchair, by studying the different mountain features that you intend to pass through. For example, what aspect and angle slopes will you be crossing?
All this information should then be backed up by checking what the snow is actually like on the ground, when you start skinning up the mountain. These checks should hopefully confirm what you suspect the conditions will be like. Is the snow powdery or damp? Soft or packed hard? Crusty or windblown? So, a Rutschblock or a pit can be dug in the snow to confirm what you have worked out from the forecasts, but remember, it will only be representative of that particular small area – a pit dug 20m away may herald different results!