The Waiho River in Franz Josef when Westland was hit with heavy rain in April. Photo: RNZ/Maia Ingoe
The West Coast and South Island headwaters will see "significant" rainfall this weekend, with orange heavy rain warnings in place until Saturday, MetService says.
Although much of New Zealand would experience warmer-than-usual temperatures over the coming days, a front would bring heavy rain to western and southern parts of the South Island, the forecaster said.
The following orange heavy rain warnings are in place:
- Grey and Buller Districts 1am-9pm Saturday; expect 100-150mm of rain in the ranges, and lesser amounts about coast. Rates could peak at 15-25mm/h about the ranges on Saturday.
- Westland, until 1pm Saturday; expect 300-400mm of rain about the ranges (possibly more in localised areas), and 100-200mm nearer the coast (especially about and south of the glaciers). Rain rates could peak at 25-35mm/h about the ranges, especially on Friday evening.
- Canterbury headwaters, south of Arthur's Pass from 9am Friday to 12pm Saturday; expect 300-400mm of rain about the main divide, and 150-200mm within 15km farther east. Rain rates could peak at 25-35 mm/h about the divide, especially on Friday evening and Saturday morning.
- Otago headwaters until 6am Saturday; expect 200-300mm of rain about the main divide, and 100-150mm within 20km farther east. Rain rates could peak at 20-30mm/h about the divide.
- Fiordland about and north of George Sound to 3am Saturday; expect 160-210mm of rain. Peak rates of 20-30mm/h.
There is also a heavy rain watch in place for Southland and eastern Clutha to 7pm Friday.
And there is a strong wind watch from midnight Friday to noon Saturday for the Canterbury high country, where northwest winds may approach severe gale in exposed places.
Northwesterlies could also become severe in Wairarapa, Wellington and Marlborough, MetService said.
Elsewhere, warm temperatures will cover New Zealand, with fine, dry and warm conditions in the east and north, MetService said.
Temperatures in some places, such as Hawke's Bay, could reach 30 degrees Celsius.
On Saturday, the North Island would be partly cloudy with isolated showers, and rain developing in the southwest later. Apart from areas affected by heavy rain warnings, the South Island would see fine spells and isolated showers.
On Sunday, there would be rain in the west of the North Island, with heavy falls, and a few showers elsewhere. The South Island would see rain developing in the southwest and fine spells and isolated showers elsewhere.
Warmer than usual
MetService meteorologist Lewis Ferris said much of the country was already experiencing warm and humid conditions.
"That is going to help to drive this very heavy rain we are going to see along the West Coast of the South Island through the rest of Friday into Saturday.
"Some parts of the Westland Ranges might see up to 400 mm of rain in around 27 hours until midday on Saturday so it is going to be quite an intense bout of rain."
The wet weather would make its way across to the North Island on Sunday but it was not expected to be as heavy.
It comes as the country is experiencing warmer than usual temperatures, with hot air travelling across the Tasman from Australia.
"Some areas on the east coast of both the North and South Islands are beginning to get quite dry and we've had a run of warm temperatures that do look to extend into the weekend with the strong northwesterlies, which does bring an increased fire risk so people need to be a bit more careful."
West Coast Emergency Management manager Claire Brown said it's closely monitoring the severe weather forecast for Westland on Friday through to Saturday morning.
"It is not unusual for these areas to receive these amounts of rainfall, however as always, we need to be closely monitoring and ready to activate, if need be, particularly for the Westland district."
An agency briefing took place Friday morning to share information and planning arrangements. Community coordinators had been contacted and West Coast Emergency Management was working closely with partner agencies
People were being warned rivers may rise quickly, surface flooding and slips are possible and driving conditions could be hazardous.
Road closure
The Milford Sound Highway has been closed as a precaution over fears warm rain and melting snow could lead to end-of-season avalanches.
MetService and NZ Transport Agency / Waka Kotahi warned motorists around Clutha and Southland they may also strike very wet conditions on Friday afternoon.
NZTA system manager for the central South Island Mark Pinner said people should check its traffic pages before setting out, and be prepared to take a break if rain got hard and made visibility poor.
Highway crews were ready for the heavy rain and watching spots like Muddy Creek in Otago, State Highway 6, where slips have caused overflowing onto the highway in the past.
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