West Coast in the firing line as winter storm parks over the South

Heavy rain warnings have extended up the West Coast as a "significant winter storm" grinds to a halt over the South Island today, bringing prolonged downpours and heavy snow to inland areas.

A complex low-pressure and frontal system is expected to remain slow-moving over the South Island, producing persistent rain and snow through Wednesday and into Thursday.

MetService has upgraded a heavy rain watch to an orange-level warning for the Grey District and Buller south of Westport, with up to 90mm of rain expected in 12 hours.

It joins a warning issued for Westland yesterday, with up to 450mm of rain forecast for the ranges and up to 200mm closer to the coast.

Heavy rain watches are also in place for parts of Canterbury and Otago, while heavy snow is expected to fall above 800m, with lesser amounts as low as 400m. That's prompted a heavy snow watch for the Canterbury high country south of the Rangitata River and parts of Otago.

NZTA has warned motorists that more than 30cm of snow could affect State Highways 8 and 80 through the Mackenzie Basin and South Canterbury on Thursday.

Up to 20cm of snow is also possible on State Highway 73 above 700m between Christchurch and the West Coast, while snowfall is expected on the Crown Range Road between 9am and 3pm on Wednesday.

“Accumulations at this level are likely to impede travel,” an NZTA spokesperson said, warning that sections of highway could be closed or restrictions introduced to prevent vehicles from becoming trapped and keep motorists safe.

Heavy Rain Warning - Orange

Grey and Buller south of Westport - 12 hours from 6pm Wednesday to 6am Thursday

Westland - 54 hours from 9am Wednesday to 3pm Friday

Heavy Rain Watch

Headwaters of the Canterbury lakes and rivers about and south of Arthur's Pass - 10 hours from 9am to 7pm Wednesday

Otago Headwaters - 9 hours from 9am to 6pm Wednesday

Heavy Snow Watch

Canterbury High Country south of the Rangitata River and Otago north of Arrowtown to Ranfurly - 18 hours from 12am Wednesday to 6pm Thursday

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