MetService issues severe weather watch for much of North and South Islands

The rain intensities predicted in the current MetService severe weather watch are less than in the downpour that flooded New Lynn on March 12. Photo / Dean Purcell.

A severe weather watch has been issued for much of the upper North Island and many parts of the South Island.

The MetService is warning of possible heavy rain over the northern North Island, western Nelson and the southern South Island.

"A slow-moving low over the Tasman Sea will direct a moist northeasterly flow over New Zealand until late Monday.

"Rain bands embedded within the flow are likely to bring periods of heavy rain with possible thunderstorms to the northern half of the North Island, western Nelson, southern Westland and Fiordland ...

"Additionally, a slow-moving east to southeasterly rain band is likely to bring a period of persistent rain to the south of the South Island during today and Monday morning."

Looking dirty black out west, Auckland! Rain bands moving through until Monday morning, keep an eye on https://t.co/7k3nmdWQwx ^GG pic.twitter.com/7aWdwnArbQ

— MetService (@MetService) March 25, 2017

Meteorologist April Clark said this afternoon that the rain bands were settling into the upper North Island, while in Canterbury and the lower North Island scattered rain was easing.

People going to Adele's concert tonight were likely to get the worst weather of the star's three Auckland shows, which began on Thursday.

Clark said the two weather systems affecting the country were "not looking as bad in terms of rain accumulations" as the torrential rain earlier this month.

That series of downpours in the upper North Island caused widespread flooding, landslips, power cuts and closures of roads and schools.

The torrent led to massive silting that was beyond the capacity of Auckland's Ardmore water treatment station, leading to a reduction in its output of drinkable water and a call from Watercare Services for people to reduce their water use by 20 litres a day.

Weather Watch said today the low in the Tasman Sea was not bringing one big band of rain.

"Instead it's bringing lines of slow moving downpours that are narrow but intense - with large dry areas around it.

"It means even within each region you can have big downpours but dry spells too."

Clark said the outlook for the country to mid-week was uncertain, "but it looks like it should be drying out a little bit".

MetService forecast:

Whangarei
Tomorrow
Occasional showers, chance heavy afternoon. Northerly dying. 26C
Tuesday
Showers becoming more frequent. Easterly. 25C

Auckland
Tomorrow
Rain eases to showers, but heavy falls possible. Northerly. 24C
Tuesday
Showers becoming more frequent. Easterly. 25C

Hamilton
Tomorrow
Rain, chance heavy​/​thundery, clearing evening. Light winds. 24C
Tuesday
Cloudy periods, showers developing. Light winds. 25C

Tauranga
Tomorrow
Thundery rain, gradually easing from afternoon. Northerlies. 23C
Tuesday
The odd shower, late rain. Light winds. 24C

Wellington
Tomorrow
Occasional rain from midday. Northerly to fresh southerly. 21C
Tuesday
Cloudy periods, morning drizzle. Southerly dying out. 21C

Christchurch
Tomorrow
Cloudy, occasional rain clearing at night. Southwesterly. 17C
Tuesday
Cloud morning and night. Northeasterlies. 19C

Dunedin
Tomorrow
Morning rain, then cloudy periods. Northeast develops. 15C
Tuesday
Morning cloud then mainly fine. Northeasterlies. 20C