Speeds are reduced and closures are possible on the Auckland Harbour Bridge as MetService warns of hail and thunderstorms in Tāmaki Makaurau.
Waka Kotahi New Zealand Transport Agency has issued an amber alert between 7am and 11am on Friday, with wind gusts expected to reach 75 to 80km/h.
Under an amber alert, speeds are reduced and some lanes on the bridge may close. The strong winds come with a warning of a low risk of thunderstorms, with a moderate risk into the evening. Any thunderstorms could increase wind gusts above what is forecast, the agency added, but this would need to track very close to the bridge to raise the alert level to red.
Motorists are urged to drive to the conditions, look out for the electronic message boards which will indicate lane closures and reduced speeds, and stay within their lane while travelling across the bridge.
Drivers of high-sided vehicles and motorcyclists are advised to avoid the Auckland Harbour Bridge and use the western ring route on State Highways 16 and 18.
"Due to predicted strong wind gusts AKL Harbour Bridge will be operating with four lanes in each direction during this morning's peak travel period. Expect delays. Take extra care especially if you are in a lighter or high-sided vehicle," the agency warned on Twitter early this morning.
Some Waitematā Harbour ferries are also being replaced by taxis due to the conditions.
Another amber alert is likely on Saturday morning, with a low risk of brief red alert level gusts, Waka Kotahi said.
MetService is forecasting showers, some heavy, with squally thunderstorms and possible hail in the evening for the Auckland region, with strong westerlies and gales gusting up to 80km/h in exposed places.
"Unfortunately we've shifted to our normal winter pattern coming in from the west - strong southwesterlies coming up the country today, bringing a blast, and that pattern is going to stay for the next few days as well," MetService meteorologist Lisa Murray told AM on Friday morning.
"Those southwesterlies will bring in thunderstorms, some unstable weather, plenty of showers [for the north].
She reiterated the risk of thunderstorms in the Northland and Auckland regions, noting that an "intense pulse" is likely to hit in the evening at around 8pm.
"If that does align, there could be some intense falls, we definitely could see some really strong gusts of wind, over 110km/h... as that pulse moves through, you could see some very heavy falls, some localised downpours, and that could push across into the Bay of Plenty and Gisborne.
"The good thing is it moves through quickly... for school holidays, not a great start for the first few days."
As of 7am, MetService has issued a severe weather warning for road snowfall on Milford Road, or State Highway 94, in the lower South Island. The warning is in place from 11pm tonight to 2am tomorrow.
A heavy snow watch is also in place from 9pm until 3pm on Saturday for Fiordland, and from 3pm on Saturday to 9pm on Sunday for Otago - south of Queenstown to Alexandra and Mosgiel - as well as Southland and Stewart Island.
"We have snow coming in down [in the south], good news for the ski fields - not so good if you're trying to get around in your car," Murray said.
"Southland can see that snow down to 100m - that dusting of snow on the roads - and some heavy accumulations from that 300m up. As you move up the South Island, say by the time you reach the West Coast, the Westland-Buller region, we're talking about 800m, maybe even down to a dusting at 600m, for snow levels there.
"And of course, the central plateau in the North Island - probably about 1100m, by midnight tonight probably down to 1000m. So right across the country there's that call to keep up to date with the forecasts, check Waka Kotahi before you head out to make sure roads are open, and wrap up and be warm."
