A MetService spokesman said an active front was expected to move slowly northeast across the South Island late tomorrow and during Saturday, bringing a disturbed westerly flow with embedded troughs.
"An area of low pressure is then expected to move east across the country on Sunday. Fronts associated with this low are likely to bring rain to much of New Zealand.''
The weather pattern meant showers were expected to start falling later on Good Friday in Invercargill and Gore, and spread to all the main centres in Otago and Southland on Saturday.
"There is a moderate confidence in rainfall accumulations reaching warning amounts in the north of Fiordland and in Westland during Saturday.''
On Sunday, the showers would remain everywhere, except Queenstown and Wanaka, where it would be sunny, albeit cool.
And on Easter Monday, the rest of the region would follow suit as a narrow ridge of high pressure develops over the lower South Island.
The sunny weather could push temperatures up to 18degC in some places and the weather is expected to remain warm and sunny for much of the rest of next week.
However, the longer-term forecast for Anzac Day shows a mixed bag for the southern region at this stage.
Temperatures are expected to remain warm around the region - ranging from 16degC to 18degC - and Dunedin and Oamaru can expect sunny weather.
Showers or rain is forecast for Alexandra, Gore, Invercargill, Queenstown and Wanaka on the day of remembrance.
