A large slow-moving trough covers New Zealand this weekend, bringing the risk of thunderstorms, heavy rain and small tornadoes.
MetService says there's a low risk of thunderstorms on Saturday for Northland, Auckland, Coromandel Peninsula, Bay of Plenty, Horowhenua, Kāpiti, northern Wellington, the Marlborough Sounds and the Grey District.
The thunderstorm risk increases to moderate in northeast Northland on Saturday afternoon and evening, with possible localised heavy rain of 10 to 20mm per hour.
"For areas near the west coast from Waikato to western Tasman, there is also a moderate risk of thunderstorms this evening and tonight," MetService said.
"These thunderstorms may bring localised heavy rain with intensities of 10 to 15mm per hour, small hail and there is also a low risk of small tornadoes."
A heavy rain watch has been issued from 5pm Saturday until 3am Sunday for the area within 20km of the Otago coast about and south of Dunedin City.
MetService said to expect 30 to 50mm of rain to accumulate, which may cause surface flooding, slips, and difficult driving conditions.
On Sunday, there is a general low risk of thunderstorms in northern and western areas during the morning.
Before dawn, there is a moderate risk of thunderstorms about eastern Bay of Plenty, coastal Waitomo, Taranaki, Horowhenua, Kāpiti, northern Wellington and the Marlborough Sounds.
The moderate risk of thunderstorms then moves to northern and western Tasman and Buller later in the morning.
"These thunderstorms may bring localised heavy rain with intensities of 10 to 15mm per hour and small hail, and there is a low risk of small tornadoes," MetService said.
Then on Sunday afternoon, there's a moderate risk of thunderstorms developing around northern Northland and spreading south later in the day, reaching northern Taranaki and the marine areas of Bay of Plenty at night.
"These thunderstorms may produce localised heavy rain with intensities of 10 to 25mm per hour and small hail," MetService warned.
"There is a low risk of the thunderstorms producing downpours with intensities of 25 to 40mm per hour."
For Buller and Westland there is a moderate risk of thunderstorms during the afternoon and evening, which could bring localised heavy rain and small hail. There is also a low risk of small tornadoes.
