Strong winds driven by a polar jet stream are sweeping across the country today, with temperatures well below average in the South Island and frost possible in some places tonight.
MetService meteorologist Alana Burrows told 1News this afternoon a jet stream lying across New Zealand was driving fast-moving fronts over the country, bringing strengthening westerly winds to the North Island ahead of a cold front, followed by a strong southwesterly flow.
"It's fast flowing, and it's helping to drive fast-moving fronts over the country, and it's partly responsible for these really strong winds," she said.
In Auckland, NZTA Waka Kotahi said gusts of up to 75-80km/h were expected on the Harbour Bridge between 3pm and 7pm, potentially affecting Friday evening peak traffic. Police also advised motorists to expect delays following a multi-vehicle crash on the bridge this afternoon.
The crash, involving three vehicles, was reported to Police just after 3.30pm. There were no reports of injury however two citybound lanes have been blocked. Motorists were advised to expect delays in both directions while the scene is cleared.
Motorists across the country were being urged to drive to the conditions and watch electronic message boards for updates on lane closures and reduced speed limits.
Earlier Friday, State Highway 3 near Te Kūiti was blocked northbound at the Te Kumi Station Road intersection after two trees fell onto the road.
MetService issued strong wind watches this morning for Hawke's Bay south of Hastings and the Tararua District, as well as the Tasman District about and northwest of Motueka. Winds could approach severe gale in exposed places until 9pm.
Snow closes roads
Snow closed parts of State Highway 73 between Arthur's Pass Village and Otira, and State Highway 7 between the turnoff to Hanmer Springs and Springs Junction, including Lewis Pass, this morning.
Both roads have since reopened, but NZTA is urging motorists to take care.
A road snowfall warning is in place for Lewis Pass from 5pm to 10pm tonight, with a further 1-2cm possible above 700 metres.
Another warning covers the Desert Road (SH1) from 1am to 4am tomorrow, where about 1cm of snow could settle near the summit.
Burrows said snow was also possible above 200 metres in Southland.
"It's that cold air mass, so the snow level can drop a bit lower," she said.
Cold night ahead
Dunedin reached a high of just 10C today, more than 6C below average, while Queenstown was expecting 11C and Invercargill 10C. Overnight temperatures are forecast to fall to 1C in Christchurch, -2C in Twizel and -3C at Mount Cook.
"It might feel quite cold overnight, actually. Some places could see frost again tonight," Burrows said.
Strong winds would add to the wind chill.
Thunderstorms are also possible today, with hail measuring 1-2cm in diameter possible across the Canterbury Plains, including Christchurch. MetService has also warned of a small risk of small tornadoes in some areas.
"We've got cold air coming in and it's colder aloft, so that means that the air is unstable and it can trigger thunderstorms," Burrows said.
Strong winds at different speeds and heights could also create rotation in the atmosphere.
"It's a good setup for them, possibly, to develop, but it's not guaranteed."
The phenomenon was framed by dark clouds and lightning. (Source: Supplied)
A small tornado spotted in Ashburton yesterday was "pretty impressive", MetService meteorologist Heather Keats told Breakfast.
"We had been talking about the risk of thunderstorms and possible small tornadoes for a couple of days, but it is still impressive when you get to see footage like that," she said.
About 800 lightning strikes were recorded, most from a single storm cell that moved over Canterbury.
Hailstones reached 3cm in diameter, large enough to damage cars and crops, Keats said.
MetService meteorologist Heather Keats says warmer temperatures and "great" weather is coming this weekend following a cold and snowy start. (Source: Breakfast)
Keats said looking forward to the weekend there would be an "uptick in temperatures".
"There will be a return to nor'westers on Sunday. Places like Christchurch looking at a high of 23C on Sunday, which looks quite nice because Stewart Island today their high is 9C. I mean, that's not pleasant."
For the rest of the country, Keats told Breakfast the weather was expected to be "great".
"It is great trick or treating weather. We have high pressure, which is everyone's best friend if you're walking around the neighbourhood. But if you are somewhat dressed somewhat scantily-clad, it is cold. So I would suggest being a werewolf, something with a fur coat," she said.
She said for large outdoor events in Auckland such as Diwali and the Auckland Marathon, "the runners will be very happy".
"It's going to be great weather for all of the weekend for Auckland for all of those outdoor events, which is great. Obviously, with Diwali, the big public firework display, it's not looking too windy, so that's great. And of course, we've got Guy Fawkes coming up next week as well."
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