MetService has issued a Severe Weather Outlook for New Zealand.

"A front over the Tasman Sea is expected to move north over the South Island on Sunday, then weaken over the North Island on Monday," says a MetService spokesperson.

The weather forecaster says there are west to northwest winds ahead of the front, which turn southwest behind it.

"There is an associated low confidence for warning amounts of rain on Sunday about the west of the South Island from Buller to Fiordland, and western Southland and Stewart Island.

"The low confidence for warning amounts of rain extends into Monday for Fiordland.'

MetService says additionally, winds are expected to strengthen for a time during Sunday.

"And there is low confidence that a wind warning will be required about the east of the South Island for severe gale northwesterlies, and about Wairarapa and Hawke's Bay south of Napier for severe gale westerlies.

"While for coastal areas of Southland and Clutha there is also low confidence on Sunday and Monday that a wind warning be required.'

The flow over the country turns westerly on Tuesday, and there is an low confidence for warning amounts of rain about Fiordland and the south of Westland, says a MetService spokesperson.

"On Wednesday, a large trough over the Tasman Sea starts to move onto New Zealand, bringing low confidence for significant amounts of rain to Buller and Westland, but the confidence for warning amounts of rain in Fiordland increases to moderate."