Storm slab avalanches large enough to bury, injure or kill a person have been sighted at Aoraki Mt Cook in the wake on heavy summer snowfall this week.
A kilometre long rockfall from Mt Silberhorn onto the Grand Plateau in the Aoraki National Park, near Mt Cook, seen on 31 December last year. Photo: Supplied / Avalanche Advisory
More than 50 centimetres of new snow has fallen since Sunday.
The Avalanche Advisory has downgraded its warning level from very dangerous to heightened conditions for all terrain until Saturday afternoon.
The advisory said loose, wet avalanche activity is likely today as the freezing level rises to 2500 metres.
Mountain Safety Council chief executive Mike Daisley said a moderate risk is still pretty high for this time of the year.
"There's great weather at Aoraki Mount Cook National Park at the moment, but just because it's nice and sunny doesn't mean the risk isn't there.
"Mt Cook always has an avalanche risk higher up on the mountain where the experienced climbers go but this warning is also lower down the mountain as well."
Daisley said there is little to no risk for day walkers in the valley below walking on the Hooker Valley Track.
"The Department of Conservation do a great job of mitigating the risk for those on the track.
"What we are seeing up higher on the mountain is loose wet avalanches, it's like when you have snow on your roof then the sun comes up and it loosens it," he said.
It's a busy time of year in the national park with lots of climbers around Daisley said.
He said all climbers need to keep a close eye on the avalanche forecast.
Elevated risk of rockfall
Daisley said there have been two major rockfalls in the national park in the last two weeks, one was the size of a rugby field coming down the mountain.
"What we are seeing with global warming is that when ice and snow recedes its receding further and further each year, which is exposing rock that hasn't been exposed in a very long time.
"The ice and snow has been holding the rock together, so as it's loosened by the heat from the sun we are seeing a lot of rock-fall."
He said no one was around when the two large rock-falls happened but the are in areas where people climb.
"It's impossible to predict rock-fall and where it will happen and the problem is we will continue to see this happen as more snow and ice recedes each year."
