Fiordland, the Nelson/Tasman Ranges, the Marlborough Sounds and Richmond Ranges, the Tararua Range, North Taranaki and the Central North Island High Country can also expect some rain.
On Monday the trough and associated rain band should move over the northern North Island, while a ridge of high pressure spreads onto southern New Zealand.
It may bring showers to the eastern Bay of Plenty and far northern Gisborne/Tairawhiti regions.
No severe weather watches or warnings have been issued as of yet.
‘Moderate risk’: Third tropical cyclone could form next week
Meanwhile, forecasters say the season’s third tropical cyclone could form within days, amid basin-wide ocean warmth across the Pacific.
The season has already brought two severe tropical cyclones: Mal, which reached category 3 strength in mid-November, and last month’s Lola, which briefly became a category 5 system before its remnants caused widespread flooding and power cuts across the upper North Island.
MetService meteorologist Stephen Glassey said multiple models are hinting at a system developing near the Solomon Islands around the middle of next week.
That came with the potential for a weak low pressure system, now positioned just northeast of Fiji, to drift westward into an area considered “favourable” for cyclone formation, with higher sea surface temperatures and light upper-level winds.
“There’s no indication that we’ll get a tropical cyclone coming toward New Zealand at this stage, but we are flagging a moderate risk of a tropical cyclone, somewhere around that area, from around the middle of next week,” Glassey said.
Niwa meteorologist Ben Noll said there was currently an “abundance” of warm water spread across the ocean, with El Niño conditions driving up sea surface temperatures in the east and a vast blob called the West Pacific Warm Pool staying in place above New Zealand.
That could fuel more cyclone activity this season - and Niwa has already forecast an elevated risk across large areas of the West Pacific.
For New Zealand, however, that risk was lower, with a subtropical ridge of high pressure above the country likely to prevent big rainmakers from travelling here with the relentless frequency of last summer.
