"The forecast is looking good for snowmaking, so that will continue in earnest on both sides over the next few days and potentially some natural snow falling early in the week."
The intermediate trails and selected upper mountain areas were expected to open within the next week, he said.
Mt Ruapehu followed the lead of New Zealand's South Island ski fields which largely opened on time earlier this month.
MetService meteorologist Rob Kerr said snow could be on the cards for higher areas of the mountain this week.
Snow was forecast for the 2000-metre mark and Mt Ruapehu might see "some action" most day, he said.
"They will actually do alright," he said.
"I don't think there'll be any significant dumps in one go but there will be a steady rate, they'll certainly get stuff most days this week they'll see a bit of precipitation up there. And at times conditions will be cool enough for a bit of snow-making even if it's going to be windy."
But the South Island ski fields might not be so lucky - with warm and dry winds sweeping Otago and Canterbury early in the week.
Showers were expected in the west and south of the South Island early in the week, with largely dry conditions expected in the east, and snow forecast for Fiordland to about 700 metres, Mr Kerr said.
Snow could grace the South Island slopes later on Thursday and Friday, he said.
"The bad news is the start of the week," he said.
"We've got strong northwest winds sweeping Otago and Canterbury...so there could be significant melting going on in the next 24-36 hours then it's largely dry for most of the week."