The slow-moving southerly front arrived in Fiordland and Westland early this week, dumping more than 300mm of rain, before slowly moving east across the South Island and north to Taranaki yesterday.
It is expected to affect the upper South Island through to Saturday morning, bringing periods of heavy rain to northwest Nelson and northern Buller.
MetService has issued severe weather warnings for that area from 10pm tonight to 6am Saturday. Rain is expected to become heavy at times from tonight through Friday and into Saturday morning with 130 to 160mm potentially falling.
There have already been reports of isolated torrential rain falling in Nelson, with one person posting a video of surface flooding this morning.
A spokeswoman at Nelson Airport confirmed at least one scheduled departure had been cancelled due to weather.
According to its website, one flight due to land at the airport had also been cancelled this afternoon.
The heaviest falls are expected from Friday afternoon until Saturday morning and hourly rates may reach 20 to 30mm.
WeatherWatch NZ head forecaster Philip Duncan said the cold front with a broad band of rain will move to the North Island today, bringing showers and even some isolated thunderstorms.
"Because of a large area of high pressure parked to the east, a low has formed off the west
coast and will stay for next few days, causing unstable conditions mainly to the northern and central North Island."
From Thursday afternoon heavy downpours and isolated thunderstorms are possible in the central part of the North Island, ahead of the front.
On Friday, showers and (isolated) thunderstorms with wind gusts along the front are likely in Taranaki, Nelson and northern Westland.
By the weekend, showers and any thunderstorms will be over the northern and eastern parts of the North Island.
Thunderstorms are possible in Northland and Auckland until Sunday.
