Big chill brings new flooding risk
Police have rescued the occupants of all 20 cars stranded on Southland's Jollies Pass.
Dozens of cars were stranded or slid off the road near Lumsden as the south's big chill began to hit.
Snow has begun to fall in the deep south with reports it is settling in many parts of Southland.
Snow showers have been reported this afternoon in Te Anau and Five Rivers, in the Hokonui hills near Gore, and at Wairio near Nightcaps. Bluff residents have also reported "teeny snow showers".
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Senior Sergeant Dave Raynes, of Invercargill, said a grader had travelled along the closed State Highway 96 between Queenstown and Lumsden, rescuing those stranded by the snow.
While some vehicles still remained stuck along the route, all drivers and passengers had now been safely transported from the area, he said.
State Highway 6 between Queenstown and Lumsden, where the Jollies are located, and the road between Mossburn and Five Rivers was closed at 6pm after snow began settling two hours earlier.
Just before 5.30pm a truck jack-knifed on the highway near Five Rivers and a rental vehicle slid off the road about the same time, a police spokesman said tonight.
This is the first of the snowfalls forecast to strike the country this week with freezing conditions expected in much of both islands as a cold snap makes its way up the country, bringing snow, rain and gale force winds to many areas.
MetService was expecting heavy snow falls above 300 metres about Canterbury and southern parts of Marlborough. Snow was also expected to low levels about Southland and southern Fiordland tonight.
MetService forecaster Dan Corbett said the overnight temperatures would be as low as -10 degrees Celsius in parts of Otago and Canterbury.
"It's a pretty darn cold air mass," he said.
By late this afternoon, drivers were asked to carry chains on State Highway 8 from Burke's Pass to Twizel, while State Highway 85 Glentanner to Mt Cook was closed to towing vehicles.
Police Constable Brent Swanson warned drivers to be cautious.
"If this snow gets worse, don't travel unless you absolutely have to. We don't want anyone doing anything silly or tempting fate," he said.
Severe weather forecaster Leigh Matheson said snow was not expected to fall in Christchurch city.
"It's more likely they will get a significant amount of rain" that could be sleety at times. Snow was expected about Banks Peninsula.
"A very strong and cold southerly flow spreads over the South Island tonight, with snow expected to lower to near sea level about southern and eastern areas," MetService said.
"This is a significant event which is expected to persist through until Friday morning."
Accumulations of snow were likely to exceed 50 centimetres above 300m, and 100cm above 500m. Smaller amounts of snow were expected below 300m.
"People should be aware that snowfalls are likely to cause widespread disruption to traffic, especially about alpine passes and higher level roads."
Below 300m, 60 to 90 millimetres of rain was expected during the period, including for Christchurch city, with 10 to 20cm of snow likely above 200m.
Severe gale southeasterlies were expected to develop about western and northern areas, from Fiordland to Nelson, including northern Marlborough and Wellington tomorrow and persist into Friday afternoon.
Damaging gusts of 130 kilometres an hour were expected in exposed places, and could possibly reach 150kmh through parts of Westland. Wind chill would be "severe" in Christchurch and "extreme" in Dunedin.
"Severe wind chill will stress livestock," MetService said.
NORTH TO GET CHILLY
In the North Island snowfalls could close the Desert Rd in coming days, but Wellington will likely be spared.
MetService duty forecaster Ian Gall said the ''very large intense low pressure system'' rolling up the South Island today would intensify as it reached the north tomorrow.
While it would reach Wellington with cold air and powerful gusts of wind, any snow would head to the west.
''The Rimutaka Hill Rd will be spared but it may be a case of only just,'' he said.
However, the snow would swing back inland early Friday and should bring snow to the Central Plateau.
By that point it would be warmer, meaning snow was unlikely to fall on lower areas.
MetService was also forecasting possible heavy showers with possible thunder for Taranaki and Taupo before Thursday night.
Occasional showers were forecast for Whanganui, Taihape and Manawatu, while Gisborne and Hawke's Bay would have fine spells with the odd shower.
Wellington, Kapiti and Wairarapa would have severe gale southerlies in exposed places tomorrow.
Westerlies could rise to a severe gale about Northland and Auckland from tomorrow night through to early Friday, gusting to 120kmh.
"Damaging winds are likely to bring down trees and powerlines, make driving dangerous for high sided vehicles and motorcycles, and can cause damage to some structures," MetService said.
South to southwest winds could rise to severe gale about Wairarapa from late tomorrow through to Friday, and in Taranaki, Bay of Plenty, Taupo and Coromandel for a time during Friday.
Today there was a moderate risk in Northland, Auckland and north of the Coromandel Peninsula of thunderstorms with heavy rain, strong wind gusts to 90kmh and small hail.
Wellington coastal roads could be hammered by "very large" waves on Friday, after the waves developed in Cook Strait tomorrow.
"Very large" waves were also likely along the Auckland west coast tomorrow, while "large" waves were expected on south-facing beaches in Christchurch.
Conditions were expected to ease around the country during Saturday.
Dunedin was cut off for a time earlier this week with North Otago bearing the brunt of widespread flooding that closed roads, including the main highway north.
Now the Otago Regional Council is warning about rivers further to the south.
Flood watches have been issued for the Taieri River, the lower Clutha River, and the Pomahaka River, which is a tributary of the Clutha.
"We have some severe weather coming through. Because the ground is saturated we're expecting those rivers to rise again and remain at high levels for ... probably at least a week," council duty flood manager Martin King said.
"There will be surface flooding if we get to peak levels again."
Risk areas included the Taieri Plains around Mosgiel, Milton, and the catchment of the lower Clutha and Pomahaka.
It is not known at this stage if Dunedin's airport at Momona is affected.
In north Otago, just 20mm to 30mm of rain would be needed for there to be surface flooding again in some areas.