Heavy rain warning on cards for sodden Nelson, West Coast

Tuesday, 30 August 2022

More heavy rain is forecast to hit the already water-logged regions of Tasman, Nelson and Marlborough from late Friday with the west coast of the South Island also in the firing line.

MetServce lead meteorologist Stephen Glassey said while high pressure would bring dry weather to most parts of New Zealand this week, the forecast was for a front to move slowly northwards over the South Island from late Wednesday bringing more heavy rain to the West Coast.

“Of even greater concern is that the front should also bring a period of rain for Tasman, Nelson and Marlborough from late Friday into Saturday, with heavy falls about the ranges likely to cause more problems in these already sodden regions.”

Glassey said the ranges of Westland could be in for about 300mm of rain later this week, and possibly 50 to 70mm in the ranges near Nelson and northern Marlborough.

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“This amount of rain wouldn't normally cause too many problems in Nelson and Marlborough but because they have already had extreme amounts of rain recently it could lead to more slips.'

On Tuesday morning, the MetService issued a severe weather warning for the South Island's West Coast and main divide from Thursday though to Saturday.

“The largest accumulations of rain are expected in Westland, south of Otira and about the main divide, where the front will become slow moving and rainfall accumulations are likely to be significant.

“Heavy rain may cause streams and rivers to rise rapidly. Surface flooding and slips are also possible and driving conditions may be hazardous.”

The warning also covers the headwaters of the Canterbury lakes and rivers, and Fiordland from George Sound northwards.

Orange heavy rain warnings and watches are also likely to be issued for the Tasman, Nelson and Marlborough regions in the coming days.

Glassey said the top of the North Island would have settled weather this week, but the MetService was keeping a close eye on a front coming down from the north that could dump more rain on Northland by late Sunday and early next week.

“The key thing here is it does look like the heaviest rain will be on the west coast of the South Island and for Nelson and Marlborough, it does not look anywhere as much as the region saw last week.

“There is still some uncertainty this far out, but it has the potential to be heavier in the ranges.”

Glassey said snow should also be on the way for the ski fields in the south over the weekend or early next week, and snow was possible for the mountains of the central North Island, but that was still “a long way off at the moment”.

“The top of the north is looking pretty dry, and will get some showers.

“But the northern rain system coming in by Sunday does have the potential to be heavy and we will be keeping an eye on that and see how the models line up over the next few days.

“It’s worth a heads up at least,” he said.

Nelson and Blenheim have already beaten their wettest winters on record by considerable margins, getting almost three times their average for winter.

Nelson airport has recorded over 700mm of rain since the beginning of June, beating their previous record of 570mm in 1970.

Meanwhile, Blenheim has had around 560mm this winter beating their previous record of 377mm in 2010.

“Elsewhere in New Zealand it is looking like a mostly settled week, with the eastern South Island expected to stay mostly dry, and the rain-bearing front not expected to reach the North Island until the weekend.”

Glassey said warmer north to northwest winds ahead of the front will make it feel like spring in a few places, especially in the east of the South Island later this week.

“However, some colder temperatures are signalled across the country next week.'