Skier critically injured after falling down Mount Temple in Banff National Park

Parks Canada says a skier was hurt when they fell down the side of Mount Temple on June 20, following a cornice collapse. Officials say a cornice at the ridgetop failed, which triggered a size 2 slab avalanche. (Supplied/Parks Canada)

A skier fell about 650 metres down the side of Mount Temple after a cornice failure last week.

Parks Canada said they were called to help on June 20. A pair of skiers had been climbing up the southwest ridge of Mount Temple, south of Lake Louise, when one fell after a cornice, an overhanging ledge or shelf of snow at the ridge of a mountain, collapsed.

The cornice fall triggered a size 2 slab avalanche, which carried the person down the steep, rocky terrain.

The skier was injured, but another skier was able to call Parks Canada for help.

"The visitor safety team responded and performed a long line rescue of the seriously injured skier and flew them directly to a staging area in Lake Louise where they were transferred to an air ambulance and flown to hospital in Calgary," said James Eastham, spokesperson for Parks Canada's Lake Louise, Yoho and Kootenay field unit in an email.

STARS air ambulance says the injured skier, a 40-year-old man, was flown to Calgary in critical condition, suffering from trauma-related injuries.

Cornices are unstable pieces of terrain and usually become even more unstable as weather changes, Avalanche Canada says.

Eastham says the skiers were well-equipped for the terrain, but all mountaineers should be cautious around ridgetops throughout Banff National Park, because these are where large cornices can develop.

"Generally, this spring has been cool and wet, and snow is lingering above treeline in most areas of the park," he said. "The lingering snow presents a number of hazards to hikers.

"It can cover trails and makes navigation difficult. Hardpacked snow can be slippery when frozen leading to slips and falls. Snow is often frozen and easy to walk on in the morning, but becomes unsupportive as temperatures rise, this can lead to post holing through deep snow which can cause exhaustion. Losing shoes is also possible."

Avalanche danger is also present in many areas, Eastham said, and backcountry users should always be careful on warm, sunny days or during rainy periods.

Eastham said the skiers were rescued quickly due to co-ordination between multiple different agencies.

"Within two hours of receiving the initial call for assistance, the injured party had been evacuated and transferred to air ambulance.

"A prompt response like this provides the highest chance for positive outcomes."