Understanding the Avalanche factors is important, before heading out on any tour you must ensure you have covered the following subjects:
1. Weather
2. Terrain
3. Snowpack
4. Human
1. Weather
Precipitation
Whether snowfalls influence the risk of an avalanche or not depends on the conditions during the period of precipitation:Critical Amount Of New Snow in the last 3 days
Favourable Conditions
No or little wind
Temperatures just below 0°, especially when the snow starts falling
Rain turning to snow
Irregular old snowpack – Well compacted
Unfavourable Conditions
A strong wind (around 50km/h or 31mph)
Low temperatures
Bad snowpack structure (numerous extreme variations of snowpack hardness, snow-covered surface frost).
Uniform and relatively loose old snowpack – Weakly bonded
Temperature
One of the general conditions to be noted during and after a snowfall is the temperature. Col, warm air, and sunshine have a huge influence on the processes of change in the snowpack and hence also on the avalanche risk.
Wind
Wind is the ultimate architect of avalanches.Just small amounts of snow combined with strong wind can lead to a critical avalanche situation.In the mountains, you should avoid freshly formed gullies, troughs and bowls, as snowdrifts accumulate there. Just as dangerous are the lee areas behind ridges, as well as the cornices above them that are in danger of taking off.Particular Caution is Required
On the lee side (snowdrift). Behind ridges, in troughs and gullies, behind slope sides
On the windward side (compacted snow). At the foot of steep ridges
2. Terrain
Slope Shape
Terrain shapes influence the formation of avalanches because they have a crucial influence on the wind direction and speed and hence also on the extent of snow fractures.Gullies, troughs and slope edges all pose high avalanche risks. These shapes of terrain help to form snowdrifts on the lee side and compacted snow build ups on the windward sideExercise – Trace your RouteTrace a route on the terrain picture that presents the lowest avalanche risk for you and your fellow skier.
The Ideal Route Makes the best use of the Terrain Shapes
Ribs, as the snow is often blown off them and snowdrifts hardly accumulate there.
Broad Ridges, as the wind hardly ever allows snowdrifts to form here either.
Humps, as they support the snowpack by means of small slope shapes.
The Tour Avoids
Steep Slopes staying away from riskier avalanche-prone areas by maintaining appropriately safe distances.
Bowls & Gullies, since these are areas where snowdrifts can often accumulate.
Cornices, because the can break off unexpectedly at any time. On the leeward side, underneath the cornice, one often finds accumulations of dangerous snowdrifts.
Slope Direction
70% of all avalanche accidents happen on north-facing slopes (W to E) and 56% in the pure north sector (NW to NE).The reason for the frequency of accidents on these aspects is that the snowpack sets more slowly due to the low amounts of sunshine. Powder, but also the danger, therefore remains in the place longer.In winter, south–facing slopes often have a more stable snowpack structure due to their prolonged exposure to sunlight.In spring, please note that the avalanche risk increases earlier on in the day for south-facing slopes than north-facing slopes.Still, 30% of all avalanches go off on a southern aspect (SE to S to SW).Bear in MindHowever, a critical avalanche situation often relates to all aspects!
Steepness
Around 97% of all avalanche accident happen on slopes with an inclination of over 30% (designated in the avalanche report as steep slopes).When determining the steepness of a slope, the steepest part of a slope that measures at least 20 x 20m (65 x 65 ft) is looked at.As a General Rule:
The steeper the slope, the more dangerous it is
The higher the danger level, the more dangerous slopes there are
In slab avalanche, regardless of the danger level, the average slope (~38°) of avalanches causing accidents is the same.
3. Snowpack
A slab avalanche can be triggered when there is a weak layer in the snowpack.The following circumstances have a positive influence on the stability of the snowpack:
Take a look at the snowpack. A thick and uniform snowpack with few variations in hardness is ideal.
A number of crossings. Heavily used slopes over the whole area before the last snowfall can reduce sliding layers and hence ensure greater stability.
4. Human
Humans represent the most important avalanche factor in recognising and avoiding the risk of an avalanche. Experience, knowledge, personal ability and appropriate behaviour are contributing factors for a safe tour. That is why conscientious route planning, attentive observation and risk-conscious decision-making are an essential part of any off-piste activity.Please click the image tabs below to find out more about our Snowsafe Avalanche Safety Centre
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Favourable Conditions
In the mountains, you should avoid freshly formed gullies, troughs and bowls, as snowdrifts accumulate there.
Just as dangerous are the lee areas behind ridges, as well as the cornices above them that are in danger of taking off.
Particular Caution is Required
In spring, please note that the avalanche risk increases earlier on in the day for south-facing slopes than north-facing slopes.
Still, 30% of all avalanches go off on a southern aspect (SE to S to SW).
Bear in Mind
However, a critical avalanche situation often relates to all aspects!
