"Although on the West Coast of the South Island rain associated with a low has started to develop late this morning and is reasonably set in now, particularly in Westland although it's all sort of approaching Buller."
Mr Doolan said the North Island would be mostly fine tomorrow to begin with, although some drizzle would develop for places such as Taranaki and Wellington.
"But everywhere else should be reasonably fine to start off with.
"Going on later into the day the front which was effecting the West Coast of the South Island is going to start to have more of an effect into the afternoon and evening across the rest of the North Island."
Scattered rain is going to develop in the afternoon, and evening, for pretty much everywhere besides eastern areas such as the Wairarapa and the Hawkes Bay where the falls might be a bit more sporadic."
It would also continue to rain along the west coast of the South Island for much of the day.
Places like Christchurch would remain reasonably fine, he said, although there was a possibility of some drizzle in the morning.
"Christchurch and Canterbury Plains are probably the only places that will escape [rain] for the course of the day."
On Sunday, there would be more rain before things cleared for some later in the day.
"Once that front has moved its way off the North Island... it's going to fine up behind that front in some areas.
"That will happen through the afternoon and evening depending where you are in the North Island. There might still be a few showers or perhaps rain in the far north."
In the South Island things would clear quickly in the morning, although there could still be some showers in western areas.
Christchurch and the Canterbury Plains would also see more rain into the afternoon and evening.
Unfortunately the rain was set to stick around into next week, Mr Doolan said.
"There is going to be another low developing, which is going to bring another front down over the North Island and that's going to bring quite considerable [rain] mostly for the North Island and that's going to basically effect the North Island and parts of the South Island through Monday and Tuesday."
Tomorrow's forecast:
Whangarei: Often cloudy. Evening showers, rain at night. Fresh northerly. High 16C Low 12C
Auckland: Cloud increasing. Evening showers, rain later. Fresh northeasterly. High 15C Low 12C
Hamilton: Cloud increasing, rain towards evening. Northerly winds. High 15C Low 9C
Tauranga: Cloud increasing, rain at night. Northerly winds. High 15C Low 11C
Wellington: Rain from afternoon. Northerly rises to gale, gusts 90km/h. High 13C Low 10C
Christchurch: Cloudy, brief morning rain. Fresh northeasterly. High 14C Low 5C
