MetService has issued a Severe Weather Watch as a burst of heavy rain and severe northwest gales is forecast for southern and central New Zealand.

An active front over the lower South Island is movning northwards during Sunday, preceded by a very strong, moist northwest flow.

This front is bringing a period of heavy rain and severe northwest gales to parts of the South Island and lower North Island.  Warnings and watches for heavy rain and strong winds are in force.

Monday, December 11
A west to southwest flow will cover northern and central New Zealand. A strong westerly flow will affect the south of the South Island, bringing a period of rain to Fiordland and westerly gales to coastal Southland.

Tuesday, December 12
A strong southwest flow will spread north over the country. A front embedded in the flow will bring a period of rain to southern and central New Zealand.

Wednesday, December 13
A front embedded in a south to southwest flow will move north over the North Island, bringing a period of rain to the island.

A west to southwest flow over the south of the South Island will strengthen later in the day, and there is low confidence the south to southwest winds could reach severe gale about coastal areas of Southland, Clutha, and Dunedin.

Thursday, December 14
A ridge of high pressure should bring settled weather to New Zealand.

Heavy Rain Watch
Area: Buller and the ranges of Westland north of Otira
Valid: 8 hours from 2:00am Sun 10 Dec to 10:00am Sun 10 Dec
Forecast: A period of heavy rain, and amounts may approach warning criteria.

Strong Wind Watch
Area: North Otago, Canterbury Plains including Christchurch
Valid: 7 hours from 8:00pm Sat 9 Dec to 3:00am Sun 10 Dec
Forecast: Northwest winds may approach severe gale in exposed places, especially about Banks Peninsula.

Heavy Rain Warning:
Heavy rain may cause streams and rivers to rise rapidly. Surface flooding and slips are also possible and driving conditions may be hazardous.

Area: Westland about and south of Otira
Valid: 11 hours from 8:00pm Sat 9 Dec to 7:00am Sun 10 Dec
Forecast: Expect 120 to 160 mm of rain from the Glaciers southwards and about the ranges, and 70 to 100 mm about the coast north of the Glaciers. Peak rates of 25 to 35 mm/h.

Area: Fiordland
Valid: 4 hours from 8:00pm Sat 9 Dec to 12:00am Sun 10 Dec
Forecast: Expect a further 50 to 80 mm of rain to accumulate north of Doubtful Sound, with lesser amounts farther south. Peak rates of 25 to 35 mm/h.

Area: Headwaters of the Canterbury lakes and rivers
about and south of Arthur's Pass
Valid: 11 hours from 8:00pm Sat 9 Dec to 7:00am Sun 10 Dec
Forecast: Expect 90 to 120 mm of rain about the main divide, and 60 to 90 mm within 15 km east. Peak rates of 15 to 30 mm/h expected about the divide.

Area: Headwaters of the Otago lakes and rivers
Valid: 6 hours from 8:00pm Sat 9 Dec to 2:00am Sun 10 Dec
Forecast: Expect a further 50 to 80 mm of rain to accumulate about the main divide, and 40 to 60 mm within 15 km east. Peak rates of 15 to 30 mm/h expected this evening about the divide.

Strong Wind Warning:
Strong wind gusts could damage trees, powerlines and unsecured structures. Driving may be hazardous, especially for high-sided vehicles and motorcycles.

Area: Wairarapa south of Tararua District, Wellington, the Marlborough Sounds, Kaikoura Coast and Ranges
Valid: 14 hours from 10:00pm Sat 9 Dec to 12:00pm Sun 10 Dec
Forecast: Severe gale northwesterlies gusting 120 km/h in exposed places, but possibly 130 km/h in Wellington early Sunday morning.

Area: Otago (excluding North Otago), Southland, Stewart Island and Fiordland
Valid: 3 hours from 8:00pm Sat 9 Dec to 11:00pm Sat 9 Dec
Forecast: Severe gale northwesterly gusting 120 km/h in exposed places.

Area: Canterbury High Country
Valid: 10 hours from 8:00pm Sat 9 Dec to 6:00am Sun 10 Dec
Forecast: Severe gale northwesterly with damaging gusts of 130 km/h in exposed places.
Winds easing from the south overnight.