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Although all self-respecting snowflakes share the same six-pointed geometry,
it is said that no two are ever identical. A snowflake is formed in the
clouds when supercooled water vapour condenses and freezes, usually onto
a microscopic foreign body, such as a particle of dust. More vapour condenses
onto the flake until it begins to fall due to its weight. The ultimate
size of the flake depends on the surrounding humidity and temperature
- the colder the temperature, the smaller the flake.
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[Photo: Dr. J. Burgess, Science Photo Library]
Snowflakes, as seen using false colour scanning electron microscope.
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Once a snow flake has landed, it begins to transform. Slowly, its sharp
edges become rounded and it begins to merge with neighbouring flakes;
the snow's surface texture changes. Snow conditions build up over a period
of months, and can be hard to grasp in a week's holiday. Conditions alter
with time of year and of day, and different slopes are better in different
seasons. In general, north-facing slopes will have good, dry snow, but
will tend to be cold. South-facing slopes are a good bet in mid-winter,
but in spring they tend to be icy early in the morning and slushy in the
afternoon. East and west slopes present a combination of these conditions.
Skiing on prepared slopes, there are a number of different types of snow
which you will encounter (for off-piste conditions see our off-piste pages).
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[Photo: Richard Price, Ski Utah] |
Packed Powder
This is what good piste skiing is all about. Over the days after a good,
dry snow fall, the powder is packed either by skier traffic or by a ratrac.
The result is a perfect surface: firm enough to bear your edges with precision,
yet yielding and painless to fall on.
Slush
At the end of every season, or during any warm spell, the snow turns to
slush. Individual crystals of snow have fused with their neighbours to form
little balls of ice, floating in a wet paste.
Skiing becomes hard work and the risk of injury is increased. But you
can still have fun: let your skis run and use a little extra speed to
make them plane over the slush.
Artificial Snow
To protect their business from the vagaries of the weather, resorts are
increasingly installing snow cannons (although even these require adequate
water and low temperatures). The snow produced is much more dense than natural
snow, making it less forgiving and more likely to become icy. Despite these
shortcomings, and the strong environmental arguments against it, artificial
snow looks like it is here to stay.
Ice
The snow condition most dreaded by the majority of skiers is ice. South-facing
slopes, which have been warmed the previous afternoon, will frequently be
icy in the morning and again once the sun leaves them in the afternoon.
Slopes which are exposed to high winds will also be among the first to become
icy, as will those which carry the greatest amount of skier traffic. It
is possible to learn to love ice, if you master
some cunning tricks. |
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