New Zealand faces the threat of thunderstorms, heavy rain and hail today as an unstable air mass hits the country.

Photo / File

Photo / File

MetService warns there’s a moderate risk of thunderstorms with heavy rain, wind gusts up to 100km/h and possible isolated small tornadoes for Central and southern Westland in the afternoon. The far north of Westland and Buller could also be hit in the afternoon and evening.

For North Otago and Canterbury, there is a moderate risk of thunderstorms with heavy rain, and hail later on Tuesday.

For Kapiti to coastal Whanganui there is a moderate risk of thunderstorms with heavy rain and strong wind gusts in the evening and at night.

There is a low risk of thunderstorms in some other areas, including the Kaikoura Coast, far west of Nelson, Wellington, Wairarapa, Taranaki, coastal Waitomo, the far south of Fiordland, coastal Southland and coastal Clutha.

MetService meteorologist Tuporo Marsters said the North Island will see some residual effects from a departing front, but the weather is expected to clear as the day progresses.

Meanwhile, the South Island will brace for a cold front arriving in the afternoon, bringing snow flurries down to around 900 metres.

“We’ve got a few road snowfall warnings in place for key routes, including Milford Road, Crown Range, and Lindis Pass, with snow expected through tomorrow afternoon and early evening,” Marsters said.

In addition to snow, cold southwesterly winds are expected to move in behind the front, particularly affecting the southern regions.

As the front clears the country late on Tuesday, the weather will improve heading in to Wednesday.

“We’ve got a ridge of high pressure moving in from the Tasman Sea, which should bring some more settled weather on Wednesday, with winds easing and temperatures becoming a bit more comfortable,” said Marsters.

However, this reprieve will be short-lived.

The ridge will retreat to the North Island by Thursday, making way for another low-pressure system developing in the Tasman Sea.

This system is expected to bring further unsettled weather across the country by the weekend, with rain and wind impacting both islands from Friday night into Saturday.

Road snowfall warnings have been issued for Lindis Pass SH8 from 12pm today to 8pm. Snow showers are expected to affect the road above about 800 meters, about 1 cm or less of snow may settle at times.

There is also a warning for Crown Range Road from 11pm last night to 8pm this evening, and for the Milford Road (SH94)Valid: 22 hours from 8 pm last night to 6 pm this evening

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