New Zealand will have a mostly fine but cooler-than-average weekend as slow-moving high pressure over the Tasman Sea sends a southwesterly wind flow across New Zealand.
But this will be followed by low-pressure systems sending fronts over the country mid-week - before a cold change coming out of the Southern Ocean "pounces on Southland".
"Fine weather will prevail across much of the country over the weekend, but there will be a few showers in some places," MetService said on Facebook.
"However, significant rain is unlikely for most, as rain-producing features, such as fronts, struggle to displace this strong high."
Then, as the high starts to move northeastwards on Sunday, westerly winds will strengthen over southern New Zealand, and a weak but cold front will sweep over the far south.
"This will bring an increase in the shower activity there, and keep a lid on the temperatures in Southland," MetService added.
"However, the strengthening westerly winds will cause temperatures to rise in the north and east of the South Island on Sunday, with many areas likely to climb into the mid-20Cs."
As the high slips away, low pressure comes down out of the Coral Sea into the Tasman Sea, while another low-pressure system drifts out of the Southern Ocean.
"A complex low and associated fronts approach from the Tasman Sea late Tuesday and Wednesday, with these fronts moving onto New Zealand on Thursday," MetService stated.
"This system is expected to bring rain and strong north-to-northeasterlies to parts of the country. On Thursday, there is moderate confidence a rainfall accumulations will exceed warning criteria for northwest Tasman and northern Buller, also central and southern Westland."
WeatherWatch said the warm humid airflow coming down from the tropics mid-week will also bring mild nights and muggy days to many areas.
This will then be followed by cold change coming out of the Southern Ocean in a week which "pounces on Southland".
