MetService advises that a large high is lying slow-moving to the east of New Zealand.

"Meanwhile, a subtropical low to the north of the country is forecast to move slowly southwards to lie west of New Zealand on Thursday, Friday and Saturday," says a MetService spokesperson.

"A strong and moist northeasterly wind flow between the high and low is expected to bring rain to much of northern and central New Zealand."

Severe Weather Warnings and Watches have already been issued for this event, and it is likely that additional watches and/or warnings could be issued in the coming days.

"On Sunday the low is expected to move east onto the north of the North Island, with a humid southeast flow strengthening over central New Zealand."

MetService says for Northland, Coromandel Peninsula and the western Bay of Plenty, there is high confidence rainfall amounts will exceed warning thresholds, through Thursday for Northland, and through to Saturday for the Coromandel Peninsula and the western Bay of Plenty.

"For Auckland, and Waikato through Thursday and Friday, and for the remainder of the Bay of Plenty and also northern Gisborne for Thursday to Saturday, there is moderate confidence that rainfall amounts will exceed warning thresholds,' says a MetService spokesperson.

"There is also moderate confidence, that northeast to east winds will rise to severe gale in areas from Northland to Taranaki and Whanganui, including Coromandel Peninsula, Bay of Plenty west of Tauranga, Taupo and Taihape."

For northwest Tasman, and also the Richmond and Bryant ranges of Nelson and Marlborough, MetService says there is moderate confidence of heavy rain on Thursday and Friday.

"For Westland, there is moderate confidence rainfall amounts will reach warning criteria on Thursday and Friday, mainly about the ranges, while for Fiordland the confidence decreases to low.

"For northern Wairarapa, the Tararua District and also Hawke's Bay south of the Wairoa District, there is low confidence that heavy rainfall will reach warning amounts on Sunday,' says a MetService spokesperson.