MetService also issued road snowfall warnings for the Milford Road, as well as the Lewis, Lindis and Arthur's passes.
"Overnight and into tomorrow morning we are going to see winter return with a vengeance across the lower South Island.
"It's really going to pay to keep a close eye on the severe weather warnings, watches and forecasts before you head out," Mr Law said.
Although the bulk of the heavy snowfall was forecast for the far south, MetService forecast snow showers for the West Coast of the South Island and around the eastern coast.
Mr Law said cold southerly winds would also continue to head northwards across the North Island into the weekend and temperatures across inland parts of the North Island could be expected to drop towards freezing.
Winds were also likely to increase in Wellington and in parts of the Nelson region overnight as a result of the front.
A severe weather warning was in place for Wairarapa, Mr Law said.
The region was buffeted by strong winds today with a bus carrying 18 school children reportedly blown off the road near Eketahuna this morning.
There were no injuries and the children got on another bus and carried on to school, said a police spokesman.