The New Zealand Mountain Safety Council is warning skiers, trampers and hunters that an incoming storm will heighten the risk of backcountry avalanches.
It said the storm was going to make large areas of the South Island backcountry very dangerous to travel in.
The MetService said a slow-moving frontal system would move up the country on Saturday and through the weekend.
Meteorologist Lisa Murray said the primary concerns for the South Island were the prolonged heavy rain which would fall as snow about the upper elevations at first but would lower heading into Sunday and Monday.
"Large accumulations of fresh snow can be expected," she said.
Aoraki/Mt Cook, Wanaka, Fiordland and Queenstown could expect up to three metre of snow in elevated areas.
'Big storm on the way'
Council spokesperson Nick Kingstone said the avalanche risk extended right up to the Nelson Lakes region, which was currently at "considerable" risk, but was due to rise.
"Yes, there's a big storm on the way, and we're expecting in some regions up to three metres-plus in terms of snowfall. The lower elevations could get significant rain, which is again partially the reason for this warning - that precipitation is likely to change to snow pack quite dramatically," Mr Kingstone said.
Avalanche forecaster Trev Streat said that amount of snow could lead to large 'storm slab' avalanches, large enough to reach valley floors, which could release without warning.
Skiers were being warned to stay within ski area boundaries where the snow safety teams were actively managing the terrain.
"Trampers and hunters also need to be aware of what dangers exist above them.
"Similar conditions are expected to be found in other areas along with main divide in areas such as Mt Aspiring National Park and Fiordland National Park," Mr Streat said.
Mr Kingstone said while the focus was on the South Island, the storm would be widespread across the country.
"It will begin somewhere around Fiordland and then slowly roll up the country.
"The message is really, for people to postpone any backcountry travel for the next 48 hours, but if you are going into those regions make sure you check the avalanche advisories very carefully," he said.
The rapidly deteriorating backcountry conditions were expected to be in place through the weekend.
Backcountry users are advised to check the NZ Avalanche Advisory avalanche.net.nz for details about the forecast regions.