Severe Winter Storm to Stall Over South Island This Week

Weather Storm Stalls Over South Island Bringing Heavy Rain

The severe weather traces back to a single system originating from a low-pressure zone near Adelaide. MetService meteorologist Devlin Lynden told 1News that the system arrives at the South Island and starts to slow down rapidly as it gets cradled between two areas of high pressure. This leaves a band of rain just sitting over the region for a prolonged period.

https://x.com/MetService/status/2091610096975700362

A heavy rain watch is already in force for the ranges of the Westland District, covering 36 hours from noon Wednesday to midnight Thursday, and MetService indicated it will be upgraded to a warning. The rain will linger from early Wednesday through Thursday and is expected to clear in the early hours of Friday as the system finally moves north. The heaviest falls will hit the Southern Alps and West Coast, where high accumulations are likely to build in the ranges.

Rising Rivers and Extended Downpours on the West Coast

While West Coasters are well used to downpours, the duration of this specific weather event sets it apart from typical systems. According to Lynden, the prolonged nature means rivers will rise higher than normal due to the sheer length of the event, generating more surface flooding across the affected areas.

In contrast to the South Island, the North Island escapes the worst of the severe weather. The North Island stays settled through the first half of the week, bringing light winds and dry weather for most residents. Strengthening northwesterlies will later drag a warmer airmass across the North Island as the week progresses, causing temperatures to climb noticeably.

Snowfall Threatens Inland Passes and Highway Travel

Colder southerly air will alter weather conditions starting Thursday, driving snow down to low levels inland. NZTA has issued warnings that inland roads could be affected from Thursday onward.

https://x.com/MetService/status/2091291890436219117

According to NZTA, more than 30cm of snow could impact State Highways 8 and 80 in the Mackenzie Basin and South Canterbury on Thursday. Additionally, up to 20cm of snow could accumulate on State Highway 73 above 700 metres between Christchurch and the West Coast. An NZTA spokesperson stated that accumulations at this level are likely to impede travel, noting that the agency may close sections of the highway or introduce restrictions to keep people safe and avoid vehicles becoming trapped.