MetService is forecasting a severe weather outlook ahead for later this week.

On Wednesday, fronts over the South Island are expected to weaken.

"North of the fronts there is likely to be a strong westerly flow over the southern North Island and there is low confidence that severe gales will be experienced in Central Hawke's Bay," says a MetService spokesperson.

"During Thursday, northwesterlies should strengthen over the country as a more active front approaches the South Island, possibly with a low as well."

Heavy rain is also expected in western areas, especially as the front moves up the South Island during Friday.

The front may become slow-moving near central New Zealand on Saturday.

"There is moderate confidence that these features will bring warning amounts of rain to Fiordland and most of Westland on Thursday and Friday and to the Grey District, Buller, Tasman, western Marlborough, the Tararua Range and Mount Taranaki on Friday and Saturday.

"There is also moderate confidence that a wind warning will be needed for severe gale northwesterlies about Marlborough, Wellington and Wairarapa on Thursday and Friday, while there is low confidence that warning strength winds will also affect Fiordland, Southland and inland areas of Otago and Canterbury on Thursday."

MetService says snow affecting some of the higher roads of the southern South Island is possible overnight Friday to Saturday, but it is unlikely that a widespread snow warning will be required.