Heavy rain, gales and snow sweep into the South Island as a powerful winter front moves up the country

A powerful winter system is sweeping into the South Island this weekend, with MetService warning of heavy rain, severe gales and falling snow as a vigorous front pushes up the country from Saturday into Sunday.

The weather agency says a strong northwest airflow is being followed by the front, which moves onto the south of the South Island before tracking north over southern and central New Zealand. The western and inland parts of the South Island are expected to be hit hardest, with several days of unsettled, soaking weather on the way for the ranges and the alpine passes.

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The standout figure is in Westland, where the ranges are forecast to collect up to 350mm of rain over 24 hours from 7pm on Friday. That is a serious dump even by the standards of a region used to West Coast deluges, and MetService says streams and rivers could rise rapidly, with surface flooding, slips and difficult driving conditions all possible.

Heavy rain warnings have also been flagged for the ranges of the Grey and Buller districts, which could see up to 130mm from late on Saturday morning into early Sunday, and for the Canterbury headwaters south of the Hurunui River, where the main divide is in line for up to 300mm from late Friday to early Sunday evening. The Otago headwaters are covered by a similar warning running from late Friday to early Sunday afternoon, while Fiordland is expected to pick up around 150mm on Friday night and Saturday morning.

Wind is the other big concern. MetService has warned of severe gales gusting to 130km/h across the Canterbury high country over a 12 hour window from 3am on Saturday. At those speeds the agency says damage to trees, powerlines and unsecured structures is possible, and that driving may be difficult, especially for high-sided vehicles on exposed roads.

Beyond the formal warnings, a wider band of the country has been placed under watches, which signal a moderate chance that conditions could worsen enough to be upgraded. Heavy rain watches are in force for the Tararua Range, the inland Buller district and Nelson Lakes from late Friday to early Sunday. Strong wind watches cover a long list of regions, including Wellington, the Wairarapa, Southland, inland Otago, western Clutha, the Marlborough Sounds and the inland Marlborough ranges.

For people in the lower North Island, that means the system is likely to make its presence felt later in the weekend as it slides north, with gusty and showery conditions reaching Wellington and surrounding districts. Anyone planning to travel between the islands, or down the spine of the South Island, would be wise to check road and ferry updates before setting out.

Snow is the part of the picture most likely to catch motorists out. Behind the front the air turns much colder, and the snow level is expected to lower over the South Island high country. MetService issues road snowfall warnings for the main alpine routes, including Lewis Pass on State Highway 7, Arthur’s Pass on State Highway 73, the Lindis Pass on State Highway 8 and the Crown Range Road, whenever snow looks likely to settle within the next 24 hours. As of Friday evening none of those warnings was in force, with the next update due at 10am on Saturday, so drivers heading into the high country over the weekend should keep a close eye on the latest advisories and carry chains.

The timing is awkward for the school holidays, which bring extra traffic onto exactly the kind of mountain roads now in the firing line as families head to the ski fields and southern lakes. Queenstown, Wanaka and the Mackenzie country sit close to several of the warning areas, and a weekend of rain at lower levels and snow up high can turn a straightforward drive into a slow and slippery one.

None of this is unusual for the middle of a New Zealand winter. The South Island’s western ranges wring enormous volumes of rain out of moist northwest flows, and the country’s alpine passes regularly close or drop to one lane when cold southerly air arrives behind a front. What makes this event worth watching is the combination, with heavy rain, damaging wind and lowering snow all stacked into the same 48 hours across a wide stretch of the country.

MetService’s standard advice in these situations is simple enough. People in affected areas should secure loose items around the property, avoid driving through floodwaters, allow extra time on the road and delay non-essential travel through the worst of the warning periods. Those near rivers and streams in the warned catchments should be ready to move to higher ground if water levels climb quickly.

The full set of warnings and watches, along with the latest timing and any upgrades, is available on the MetService warnings page, which is updated through the weekend as the front moves through. Further detail on the system has been reported by the New Zealand Herald.

Are you in one of the warning areas this weekend, or planning to travel through the alpine passes? Tell us what the weather is doing where you are in the comments below.

This article was written by AI, briefed to report the facts, hopefully without some of the bias people bring to the job 🙂