By Craig Anderson BBC Highland reporter

Walkers and climbers are given warning of treacherous conditions

Every day during the winter a team of observers trudges into the most popular winter climbing and walking areas to check snow conditions and forecast the avalanche risk.

Many winter mountain accidents are caused by snow avalanches.

Some mountaineers may be hit by hundreds of tonnes of cornice or wind-slab cascading on them from above.

But more likely is the possibility that their own footsteps will cause the ground to slip away from under their boots, carrying them down the slope they've been negotiating.

"It can be like drifting down in some soft, fluffy snow, which nonetheless may bury and asphyxiate you," says Blyth Wright, co-ordinator of the SAIS.

As an experienced international climber, he has personal experience of being caught in avalanches.

He said: "Other times if we've got hard-slab avalanches - and these are very common in Scotland - it might be like tumbling uncontrolled down a hillside accompanied by 10,000 tonnes of concrete blocks."

Steer clear

Mark Diggins, one of the observers employed to carry out daily checks, explains that by digging a pit and measuring the temperature at various depths in the snow he can assess if it's unstable.

"It's not so much that you'll get engulfed. It's more that a small area of snow will avalanche and carry you somewhere," he said.

The SAIS is paid for by the government through SportScotland and is based at the Glenmore Lodge outdoor training centre.

There are plans to expand its remit and establish an avalanche research centre in Scotland.

Depending on conditions, the risk is classed from 1 to 5 - low to very high. Blyth Wright says his aim is not to discourage people from venturing into the hills, although many climbers will abandon their expeditions if the risk is 4 or 5.

Others will still set off, though in the knowledge that they should steer clear of areas where there is a danger of avalanches.