Heavy snow and gale force winds will hit parts of the country this weekend, causing widespread travel disruption and dropping snow in places that do not normally see it.
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The MetService said "an exceptionally cold outbreak" was set to grip much of the country, sweeping over the lower South Island tomorrow evening and moving up the North Island on Sunday.
The low temperatures would linger over the country until Wednesday with the coldest day likely to be Monday.
"The combination of cold winds and rain or snow may bring extreme wind chill and cause significant stress to new-born livestock," MetService weather ambassador Bob McDavitt said.
"Snowfall is also likely to disrupt traffic on some roads. This event is likely to last longer than the snow storm of 25th July."
Heavy snow was forecast for Southland, southern Otago, including Dunedin, Christchurch and the Banks Peninsula.
Wellington, the Wairarapa, Taranaki, Hawke's Bay and possibly high parts of Auckland and Northland were also expected to get snow.
WeatherWatch.co.nz head weather analyst Philip Duncan said data this morning, from the same source that accurately predicted snow in several main centres last month, suggested snow would fall in Napier, Hastings, Masterton, Dannevirke, Palmerston North, Hawera, Stratford and potentially Wanganui.
Snow was unlikely to settle for long at sea level, or near sea level, in the North Island.
However, it could cause travel issues for motorists right down to sea level from Wellington to Wairarapa, Hawke's Bay to the Central Plateau, Canterbury to Marlborough, and Southland to Otago. Highways as far north as Gisborne could be affected.
Very heavy snow could fall on the North Island mountain ranges, Duncan said. Snow showers were predicted for the Desert Road from Sunday night until Wednesday.
A very large southerly swell was expected in Cook Strait from Monday to Wednesday, potentially affecting ferry crossings.
"This snowstorm is really the perfect storm," Duncan said.
"We have a high stretching over 6,000km from the tropics to Antarctica expected to form in the Tasman Sea, meanwhile a low in the central Tasman Sea will move east into the Pacific Ocean over the weekend, combining with a Southern Ocean low.
"All three systems will work together to provide an impressive southerly blast rarely seen here."
Farmers, in the middle of lambing season, were advised to move livestock.
- The Dominion Post