Tasman tempest may bring flooding rain, damaging wind Friday night and Saturday

A potent storm strengthening over the Tasman Sea will move over New Zealand tonight and pummel the country with heavy, possibly flooding, rain and damaging wind gusts.

Steady rain will spread over the northern South Island and southern North Island late this afternoon.

Torrential, windswept downpours are expected tonight across the northern Tasman region, Nelson, parts of northern Marlborough. On the North Island, the heaviest of the rain will extend from Taranaki through Manawatu-Whanganui and into Wellington.

In some spots, rain will exceed 100 mm overnight, leading to areas of surface flooding and slips.

Locally Damaging Winds from Taranaki to Cook Strait Early Saturday 

A squall line of intense rain and wind is forecast to pass through the northern South Island and southern and western North Island between 2 and 6am tomorrow. During this time, frequent lightning is possible along with northerly wind gusts higher than 130 km/h in places. Gusts of this magnitude are more typically associated with category two tropical cyclones.

The worst of the wind will pass through Wellington between 3 and 6am on Saturday.

The line of heavy rain and thunderstorms is forecast to move through Auckland from 5-9am with wind gusts possibly over 100 km/h. By late tomorrow morning, skies will begin to clear in Auckland, giving way to a warm but windy afternoon.

Squall Line to Race through Auckland Saturday Morning 

Christchurch and the rest of mid-Canterbury will also have a round of bad weather tomorrow. Rain early in the morning and strong wind gusts at the coast will move inland during the afternoon as gusty showers continue. Wind gusts in the city might exceed 70 km/h during the afternoon.

Tomorrow night another round of heavy rain and strong, possibly damaging winds is possible for the west of the North Island. Sunday will continue to be unsettled with gusty showers across the North Island with isolated showers and chilly temperatures in the South Island.

Going back to work and school on Monday, much of the country will have windy and unseasonably chilly weather with showers.