Heavy rain is forecast for the west of the South Island, and severe northwest gales for central and southern New Zealand, says a MetService spokesperson.

Warnings and Watches are in force for heavy rain and strong winds.

"A strong west to northwest flow covers the country,' says a MetService forecaster.

"Fast moving embedded fronts bring bursts of heavy rain to western parts of the South Island, with significant spillover into the Canterbury and Otago headwaters."

The MetService warns that gale or severe gale west to northwesterlies are expected to affect many areas in central and southern New Zealand.

"Please stay up to date with forecasts in case any changes are made to the current warnings or watches, or new ones are added."

Heavy Rain Watch
Area: Nelson Lakes
Valid: 10 hours from 12:00pm Sun 17 Sep to 10:00pm Sun 17 Sep
Forecast: A period of rain with some heavy falls, and amounts may approach warning criteria.

Area: North Otago, Dunedin and Clutha north of Balclutha
Valid: 12 hours from 12:00am Sun 17 Sep to 12:00pm Sun 17 Sep
Forecast: A period of rain with heavy falls possible, and amounts may approach warning criteria.

Strong Wind Watch
Area: Hawke's Bay south of Wairoa, and the Central North Island high country from south of Lake Taupo to Taihape

Valid: 17 hours from 4:00pm Sun 17 Sep to 9:00am Mon 18 Sep
Forecast: West to northwest winds may approach severe gale in exposed places.

Area: Horowhenua and the Kapiti Coast
Valid: 16 hours from 9:00am Sun 17 Sep to 1:00am Mon 18 Sep
Forecast: Northwest winds may approach severe gale in exposed places.

Area: Tasman northwest of Motueka
Valid: 15 hours from 6:00am Sun 17 Sep to 9:00pm Sun 17 Sep
Forecast: Northwest winds may approach severe gale in exposed places.

Area: Clutha, Southland, Stewart Island, and Fiordland south of Milford Sound
Valid: 40 hours from 8:00pm Sat 16 Sep to 12:00pm Mon 18 Sep
Forecast: From Saturday evening to early Sunday morning, and again from Sunday afternoon till late Monday morning, west to northwest winds may approach severe gale in exposed places.

Note, there is a higher risk that winds may exceed severe gale in some areas from Sunday afternoon to late Monday morning, and this Watch may upgraded to an Orange Warning for that period in the next issue.

Area: Canterbury Plains and Christchurch including Banks Peninsula
Valid: 24 hours from 8:00pm Sat 16 Sep to 8:00pm Sun 17 Sep
Forecast: Northwest winds may approach severe gale in exposed places.

Area: Otago excluding Clutha
Valid: 38 hours from 8:00pm Sat 16 Sep to 10:00am Mon 18 Sep
Forecast: From Saturday evening to early Sunday morning, and again from Sunday afternoon till late Monday morning, west to northwest winds may approach severe gale in exposed places

Heavy weather 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 north of Otira, and Buller
Valid: 18 hours from 2:00am Sun 17 Sep to 8:00pm Sun 17 Sep
Forecast: Expect 80 to 120 mm of rain about the ranges, and 40 to 60 mm near the coast. Peak rates of 10 to 20 mm/h expected Sunday afternoon and evening. Thunderstorms possible.

Area: Westland south of Otira
Valid: 22 hours from 8:00pm Sat 16 Sep to 6:00pm Sun 17 Sep
Forecast: Expect 150 to 200 mm of rain about the ranges, and 50 to 70 mm near the coast. These amounts are in addition to the rain that has already fallen. Peak rates of 15 to 25 mm/h expected about the ranges from late Sunday morning. Thunderstorms possible.

Area: Fiordland north of Doubtful Sound
Valid: 16 hours from 8:00pm Sat 16 Sep to 12:00pm Sun 17 Sep
Forecast: Expect 80 to 120 mm of rain on top of what has already fallen. Peak rates of 10 to 15 mm/h expected Sunday morning. Thunderstorms possible.

Area: Fiordland about and south of Doubtful Sound
Valid: 12 hours from 8:00pm Sat 16 Sep to 8:00am Sun 17 Sep
Forecast: Expect 40 to 70 mm of rain on top of what has already fallen. Peak rates of 10 to 15 mm/h.

Area: Headwaters of the Canterbury lakes and rivers south of Arthur's Pass
Valid: 18 hours from 12:00am Sun 17 Sep to 6:00pm Sun 17 Sep
Forecast: Expect 140 to 180 mm of rain about the main divide, and 80 to 110 mm within 15 km farther east. Peak rates of 15 to 25 mm/h expected about the divide. Thunderstorms possible.

Area: Headwaters of the Otago lakes and rivers
Valid: 15 hours from 11:00pm Sat 16 Sep to 2:00pm Sun 17 Sep
Forecast: Expect 100 to 130 mm of rain about the main divide, and 70 to 90 mm within 15 km farther east. Peak rates of 10 to 20 mm/h expected about the divide. Thunderstorms possible.

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: The Tararua District and Wairarapa about and north of Carterton
Valid: 20 hours from 6:00am Sun 17 Sep to 2:00am Mon 18 Sep
Forecast: Severe gale northwesterlies with damaging gusts of 130 km/h in exposed places.

Area: Wairarapa south of Carterton, Wellington, and the Marlborough Sounds
Valid: 20 hours from 4:00am Sun 17 Sep to 12:00am Mon 18 Sep
Forecast: Severe gale northwesterlies with damaging gusts of 130 km/h in exposed places.

Area: Marlborough excluding the Sounds
Valid: 20 hours from 2:00am Sun 17 Sep to 10:00pm Sun 17 Sep
Forecast: Severe gale northwesterlies gusting 120 km/h in exposed places.

Area: Canterbury High Country
Valid: 24 hours from 8:00pm Sat 16 Sep to 8:00pm Sun 17 Sep
Forecast: Severe gale northwesterlies with damaging gusts of 130 km/h in exposed places.