The rain was poised to stall over the top of the North Island this weekend.
“The rain is trapped between two very powerful high-pressure zones and one of those highs is also feeding in tropical air this weekend to the rain,” it said.
Eastern Bay of Plenty and Tairāwhiti looked to be the most exposed to rain heavy enough to cause slips and localised flooding, the forecaster said.
Its modelling showed more than 200mm of rain was expected to fall in the eastern region between now and Tuesday.
Northland, Taranaki across to Taihape and Wellington are the latest North Island regions to have heavy rain watches put in place.
Northland is expected to have a 26-hour deluge from 9pm on Saturday until midnight on Sunday. MetService says there will be periods of heavy rain that may see the watch increase to warning status.
Rain is expected to start falling in Wellington and neighbouring Kāpiti Coast from 4am on Saturday and continue for six hours. Forecasters warn another spell of heavy rain is possible overnight on Saturday or during Sunday, with fresh alerts likely to be issued closer to the time.
In the centre of the island, the rain is expected to start falling in Taranaki across to Taihape at noon and last for 20 hours.
MetService said a slow-moving front over the South Island was expected to move onto the North Island tonight and continue moving slowly eastwards across the island during the weekend.
As the front moved across the north on Sunday and Monday, a low was expected to develop, with gales likely to affect the top half of the island.
There are snowfall warnings in place for South Island alpine passes, with heavy snow falling across the afternoon and evening. Up to 25cm is expected to fall on Porters Pass.
A heavy snow warning is in force across parts of Canterbury today, with MetService warning it could disrupt travel and damage trees and powerlines.
