Heavy rain warnings and strong wind watches are in force across central and southern New Zealand as a slow-moving front drifts northward, bringing up to 400mm of rain to isolated western ranges.
MetService reported that the system would deliver heavy northwesterly rain to the western South Island and the Tararua Range starting Sunday afternoon. Orange heavy rain warnings apply to the Westland District, the headwaters of the Canterbury lakes and rivers south of Arthur’s Pass, the Tararua Range, and the ranges of the Buller and Grey districts.
Forecasters expect the heaviest rainfall in the Westland ranges and Canterbury main divide, where totals could reach 300 to 400mm. Peak rates of 30 to 40mm per hour are anticipated in those areas on Monday morning.
Additional accumulation totals vary by location across the affected regions. The Tararua Range is projected to receive 100 to 150mm of rain, while the Buller ranges are expected to collect between 90 and 130mm. The ranges of the Grey District are forecast to record 100 to 130mm of precipitation.
Specific active timeframes for the orange heavy rain warnings include the Westland District from midday Sunday to 1pm Monday, and the headwaters of the Canterbury lakes and rivers south of Arthur’s Pass from 2pm Sunday to 2pm Monday.
The warning for the Grey District ranges spans from 10pm Sunday to 2pm Monday, while the Tararua Range warning is effective from 3pm Monday until 4am Tuesday. The ranges of the Buller District remain under the warning from 3am until 5pm Monday.
“Streams and rivers may rise rapidly. Surface flooding, slips, and difficult driving conditions possible,” MetService warned, advising residents to “clear your drains and gutters to prepare for heavy rain. Avoid low-lying areas and drive cautiously.” The forecaster added that the warnings carry a minimal likelihood of being upgraded to red, though surface flooding and slips remain possible alongside rapidly rising waterways.
The New Zealand Transport Agency said that maintenance crews were on standby to respond to roadway flooding, slips, and debris.
“Heavy rain means slippery roads and drivers should think about adjusting their speed and travelling distances, avoiding sudden braking, and staying visible,” NZTA said, adding that motorists should steer clear of floodwaters where depth remains uncertain or hidden hazards might lurk.
Alongside the precipitation, strong wind watches are active for the Canterbury High Country from 10pm Sunday to 10am Monday, and for Wellington and the Wairarapa south of Masterton from noon until 8pm Monday. MetService cautioned that “Northwest winds may approach severe gale in exposed places,” noting a moderate chance that the wind watches could be upgraded to full warnings.