New Zealand Mountain Safety Council (MSC) chief executive officer Mike Daisley said many of the South Island’s mountains bore the brunt of the recent weather system which brought "significant" snowfall.
However, the extremely variable snowfall amounts during July had left some of the avalanche forecasting regions with unseasonably low snowpacks, and others with plenty of snow.
He said the Southern Lakes region, and the main divide south of Rakaia, had been extremely dry recently and this had resulted in a weak snow pack.
"The snowfall forecast over the next few days will fall on this weak snowpack across the South, especially in regions where persistent weak layers have developed throughout July.
"As a result, the avalanche danger will increase dramatically across the Southern Lakes region," he said.
Of the 13 avalanche forecasting regions Wanaka, Queenstown, Mt Aspiring, Arthur’s Pass and Aoraki/Mt Cook were already classified as "high" avalanche danger.
Further changes to the avalanche danger ratings were likely as the present storm progressed, he said.
"Back-country travel is not recommended until more information can be gathered and the avalanche hazard fully assessed."
He said the New Zealand Avalanche Advisory (NZAA) forecasters needed time to reassess the hazards, and while they did this, it was strongly advised people stay out of the back-country.
"This includes mountaineering, back-country skiing and alpine tramping and hunting."
