MetService is forecasting an unsettled westerly flow covering New Zealand on Tuesday, with embedded fronts bringing rain or showers to many western and southern areas.

"There is low confidence of northwesterly or westerly winds reaching severe gale at times about exposed parts of inland Central Hawke's Bay, Tararua District, Wairarapa, Wellington, Marlborough and the Canterbury High Country," says a MetService spokesperson.

On Wednesday, a northwesterly flow is expected to continue over the southern South Island, while a ridge of high pressure spreads onto northern and central New Zealand.

"There is low confidence of northwesterlies reaching severe gales about exposed parts of southern Fiordland and Southland, including Stewart Island, late in the day."

A ridge of high pressure should cover the North Island on Thursday, while a northwesterly flow covers the South Island with a cold front moving onto the southern South Island during the day.

"There is low confidence that rainfall could reach warning criteria about the southern Westland ranges, Fiordland and mainland Southland."

On Friday, September 13, a northerly flow should cover northern and central New Zealand, while a cold front with rain is likely to lie slow moving over the southern South Island.

"There is low confidence of warnable amounts of rain about southern Westland, northern Fiordland, and parts of inland Southland and Otago."