It is important on a daily basis to get the avalanche hazard forecast and weather reports because it will give you information from which you can begin to determine the avalanche risk.
What to look for in snow and weather forecasts
What is the avalanche hazard bulletin?
This will advise your where the most hazardous areas are.
Where is the freezing level?
If it is cold – well below zero celsius – weak crystals remain and can continue to destabilise the snowpack.
If it is warm – around zero and above, the snowpack will eventually become more bonded and stable.
If it is warm after a recent heavy snowfall there is high avalanche risk for a few days.
When was the last snowfall?
If it snowed a long time ago the snow has a higher possibility of becoming more stable especially if is warm (around zero celsius and above).
If the snow is shallow (around 1m) and it has been well below zero celsius in temperature for a number of days, then this is a dangerous situation as weak crystals will develop in the snowpack.
How much fresh snow has fallen?
Around 30cm of new snow is a critical amount from which avalanches develop – wait at least 24 hours to allow the snow to stabilise.
What is the rate of the snowfall?
If it is snowing at a rate greater than 2.5cm per hour – this is a high avalanche hazard situation.
What is the total snow depth?
If the total snow depth is shallow – around 1m and it is cold, well below zero celsius (usual in the early winter), this will develop a weak snowpack.
If the total snow depth is shallow – around 1m and it is warm – around zero celsius and above, then the snowpack will become more stable.
If the snowpack has been deep from the early winter 3m or so, then weak crystals do not form so readily.
If the snowpack is deep and recent it may be lying on a weak lower layer – this increases the avalanche hazard.
Where is the wind blowing from?
For example, if the wind is blowing from the west and it is snowing it will accumulate poorly bonded snow onto eastern slopes. This weak layer is know as ‘windslab’ or ‘plaque a vent’.
It does not need to be snowing – e.g. the wind can scour on the western slopes and transport the scoured snow onto eastern slopes. Here, it will produce cornices with lethal windslab below it. Windslab snow is very hazardous and will require warm temperatures for it to eventually stabilise.