The country is in for a drenching as forecasters expect a looming weather system will bring rain up to two times the April normal from tonight.
It's prompted West Coast Emergency Management to start preparations for the incoming weather and warn residents to review their emergency plans.
MetService said starting on Monday night a "major weather system" will bring rain to New Zealand over the next few days, starting in the west.
"A front is expected to move northwards over Fiordland on Tuesday, and become slow moving in Westland during Wednesday and Thursday," MetService said.
"A humid north to northwest flow precedes the front, and is expected to bring periods of heavy rain to Fiordland and Westland, and strong north to northwest winds to Fiordland and the Canterbury High Country."
MetService has issued orange heavy rain warnings for parts of Westland, Otago and Fiordland from Tuesday morning.
Heavy rain watches have also been issued for the Grey District, parts of Westland District, headwaters of Canterbury Lakes and Rivers and parts of Fiordland.
A strong wind watch has been issued for Canterbury High Country and Fiordland.
NIWA said some rainfall totals may reach “one to two times the April normal” and "flooding is a concern".
From Thursday, the rain starts to move northwards. MetService said a series of lows could develop on the slow-moving front over the South Island and strong northerlies and rain are expected to move onto the North Island.
"For the northern and central North Island, the Buller and Grey Districts and northern Fiordland there is low confidence that a rain warning will be needed.
"Additionally, there is low confidence for severe northerly gales in Taranaki, Wellington, southern Wairarapa and northern Marlborough."
On Friday, the front and associated lows are forecast to slowly move east across the North Island, while southerly winds spread up the South Island.
There is a moderate confidence of warning amounts of rain about central areas of the North Island and the upper South Island.
"Outside these areas there are many districts with low confidence that warning amounts of rain will fall, covering most of the north and central North Island, the Tararua Range, the Buller, Grey and Westland Districts, South Canterbury and eastern Otago," MetService said.
"For eastern Bay of Plenty, Tairawhiti/Gisborne and the Wairoa District there is also low confidence that severe gale northerlies will be experienced."
Emergency planning for possible Westland weather event
West Coast Emergency Management (WCEM) has started planning and preparations for the weather warning issued by MetService.
"A precautionary approach is being taken in the event we may need to activate a Emergency Operation Centre (EOC). Local community coordinators are also being contacted to check-in, and test alternate communications in some areas," a WCEM spokesperson said.
WCEM said it has received queries from the public concerned about the possible impact this may have in the area.
"WCEM asks everyone to keep up-to-date with the forecast and take precautions. This is a good time to review your emergency plans for home or work, and if travelling to check you have some emergency supplies (water, food, warm clothing) with you," the spokesperson said.
WCEM is meeting with other agencies on Tuesday to assess the forecast and update each other on planning arrangements.
The West Coast is not unaccustomed to large rainfall, however we are wanting people to keep an eye out and to take care," WCEM Group Manager Claire Brown said.
People in the area are strongly encouraged to keep up to date with the latest information by checking state highway conditions at https://www.journeys.nzta.govt.nz/traffic/southisland · monitoring weather conditions at https://www.metservice.com/warnings/home.
Here's MetService's full weather warnings:
Heavy Rain Warning - Orange
Impact: 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 District south of Hokitika
Period: 57hrs from 9am Tue, 9 Apr - 6pm Thu, 11 Apr
Forecast: Periods of heavy rain. Expect 600 to 800mm to accumulate about the ranges, and 200 to 300mm about the coast. Peak rates of 20 to 30 mm/h about the ranges. This is a significant heavy rain event with the potential for upgrade to a Red Warning.
Area: Headwaters of the Otago Lakes and Rivers
Period: 23hrs from 9am Tue, 9 Apr - 8am Wed, 10 Apr
Forecast: Expect 200 to 300mm about the main divide, and 100 to 150mm within 15km further east. Heavy rain is expected to return later on Wednesday and become more widespread through Otago. This warning may be extended, or a Watch issued, closer to the time.
Area: Fiordland about and north of George Sound
Period: 26hrs from 4am Tue, 9 Apr - 6am Wed, 10 Apr
Forecast: Periods of heavy rain. Expect 150 to 250 mm of rain. Peak rainfall rates of 20 to 30 mm/h. Heavy rain is likely to return later on Wednesday and this Warning may be extended, or a Watch issued, closer to the time.
Heavy Rain Watch
Area: The Grey District, and Westland District about and north of Hokitika
Period: 48hrs from 6pm Tue, 9 Apr - 6pm Thu, 11 Apr
Forecast: Periods of heavy rain, and amounts may approach warning criteria.
Area: Headwaters of Canterbury Lakes and Rivers
Period: 30hrs from noon Tue, 9 Apr - 6pm Wed, 10 Apr
Forecast: Periods of heavy rain. Rainfall amounts may approach warning criteria within 15 km east of the main divide.
Area: Fiordland south of George Sound
Period: 20hrs from 4am - midnight Tue, 9 Apr
Forecast: Periods of heavy rain, and amounts may approach warning criteria. Heavy rain may return later on Wednesday and this Watch may be extended.
Strong Wind Watch
Area: Canterbury High Country
Period: 24hrs from noon Tue, 9 Apr - noon Wed, 10 Apr
Forecast: Northwest winds may approach severe gale in exposed places.
Area: Fiordland
Period: 24hrs from 6pm Mon, 8 Apr - 6pm Tue, 9 Apr
Forecast: North to northwest winds may approach severe gale in exposed places. Note: Watch extended to all of Fiordland.
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