Danger Of A Persistent Weak Layer In The Backcountry

Danger Of A Persistent Weak Layer In The Backcountry

Media Release: Mountain Safety Council & NZ Avalanche Advisory

For Immediate release

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The Mountain Safety Council who operate the NZ Avalanche Advisory are advising backcountry skiers, snowboarders, hunters and trampers that current snowpack conditions throughout many parts of New Zealand present a heightened avalanche risk. Backcountry travel is only suitable for experienced user who can identify snowpack concerns and select safe travel terrain.

Mountain Safety Council avalanche forecasters have identified a ‘persistent slab’ danger which is present throughout many areas of the country, in particular Queenstown, Wanaka, Aoraki/Mt Cook, Fiordland and Tongariro. However, this persistent weak layer could extend to other regions. The nature of the problem lies deeper than the recent fresh snow and can become reactive under certain conditions. IFMGA guide and co-ordinating forecaster Jamie Robertson said that

“Persistent slabs have the ability to be triggered by smaller avalanches and step down to the weaker layers, thus the avalanches can be a lot bigger than expected.”

“This is a complex problem and requires very careful management. We advise people to stick to low-angle terrain or aspects that don’t have persistent layers.”

“It’s imperative that people check all the details of the advisory, not just the headline danger level. There’s critical information within these forecasts that help to guide people to safe aspects and elevations.”

With significant snowfall predicted for the weekend the current avalanche dangers are likely to persist into next week. Robertson said that the recent avalanches are indicative of the kinds of large avalanches possible at the moment.

“The problem relates to more than just the new snow so management is more about avoiding the slopes that might have the persistent layers, you can’t trick the snowpack.”

Mountain Safety Council Communications Manager Nick Kingstone said that the advisory has a ‘public observation’ function on the site and that the council is encouraging the public to get involved in helping to keep the backcountry community safe.

“The NZAA - avalanche.net.nz - has a ‘public observation’ feature on the homepage where people can enter their own observations. Our forecasters really value as much data as possible when they’re forecasting conditions in their region. It’s ideal if they add a photo if possible.

“If the forecasters have got dozens of recent observations of snow conditions or avalanches they’re able to refine their forecast. Ultimately, these forecasts are a vital decision-making tool and we’re relying on the backcountry users to add to the safety efforts for the wider community.”

“Excitingly, this year we’ve got great monthly prizes to incentivise people to add their observations. Head to the NZAA competitions page for more details”

Ten of the advisories twelve regions are at ‘Considerable’ danger rating described as: Dangerous avalanche conditions Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

More information is available at avalanche.net.nz or at the mountain safety council’s Facebook page dedicated to the snow and alpine community.

ENDS

Snowpack video demonstrating a weak layer. This was shot a few weeks ago : https://youtu.be/v9YMXBd-I4w

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