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Three conditions must be present to start an avalanche:
Avalanches generally occur on slopes steeper than 35 degrees.
Recent avalanches, shooting cracks, and “whumpfing” are signs of unstable snow.
Sometimes it doesn’t take much to tip the balance; people, new snow, and wind are common triggers.
There are two main types of avalanches
Slab avalanches occur when a cohesive slab of
snow releases over a wide area.
Sluff avalanches occur when loose superficial snow
releases at a point and fans out as it descends.
Am I on or below slopes that can avalanche?
Is the terrain steep enough to avalanche?
If not, is it connected to steeper terrain?
Avalanches most often occur on slopes steeper than 30 degrees.
The best way to determine whether the terrain is steep enough is to measure it with a slope meter.
Slopes less steep than about about 30 degrees rarely avalanche, while slopes steeper than about 35 degrees can and often do avalanche. If a slope is steep enough to be exciting … it is probably 35
degrees or steeper! Just because the slope is steep enough to avalanche
doesn't mean that it will; the snow must also be unstable.
Is the snow stable?
A typical snowpack is actually a series of different layers stacked on top of each other. These layers are formed by precipitation, varying temperatures, and wind events that occur throughout the winter. The layers can deviate from very hard icy layers to very soft loose "sugary" layers.
Refer to your local avalanche center for current snowpack conditions!
Weather is the carpenter that constructs the snowpack
The harder it snows or rains, the
more difficult it is for the snowpack to adjust, and the more likely it is for the snowpack to avalanche.
Wind can deposit snow at an incredible rate and often leads to avalanching on the leeward (down wind) sides of ridges and other terrain features.
Rapid warming can cause the
surficial snow to lose strength and become more prone to avalanching.
Get more training!
Visit http://avalanche.org/education.php for local course providers.