New Zealand: Heavy rain, snowfall, and strong winds forecast across southern region through at least July 30

Heavy rain, snowfall, and strong winds are likely across South Island through at least July 30. A complex trough is forecast to track across the South Island July 29, bringing severe weather. As of July 28, the New Zealand National Meteorological Service (MetService) has issued the following weather warnings:

• Orange (middle level on a three-tier scale) Heavy Rain Warning: Tasman northwest of Motueka, and North Otago, Dunedin, and Clutha southeast of Raes Junction

• Yellow Heavy Rain Watch: Mount Taranaki, Westland District, and Southland and Clutha about and northwest of Raes Junction

• Yellow Heavy Snow Watch:  South Canterbury, including the foothills and inland areas of Otago and Southland, as well as eastern Fiordland

• Yellow Strong Wind Watch: Westland and the Fiords

• Road Snowfall Warning: Lindis Pass (SH8), Crown Range Road, and Milford Road (SH94)

Authorities will likely issue new alerts or update/rescind existing advisories as weather conditions change over the coming days.

Where precipitation falls as rain, flash and areal flooding is possible. This may occur in low-lying communities near watercourses and other large bodies of water and in urban areas with easily overwhelmed stormwater drainage systems. Sites downstream of large reservoirs may be subject to flash flooding after relatively short periods of intense rainfall.

Precipitation could fall as snow in the higher elevations over the coming days. Wind gusts could cause blowing and drifting snow; decreased visibility is likely in mountainous areas. Rain-induced landslides are possible in areas of elevated terrain; there is also the possibility of avalanches in mountainous areas where the snowpack has become unstable due to heavy snowfall. Power outages are likely throughout the affected area.

Floodwaters and related debris will likely render some bridges, rail networks, or roadways impassable, impacting overland travel in and around the affected area. Flooding in urban areas will probably cause significant traffic congestion. Heavy snow will make driving hazardous in some areas; authorities will likely implement temporary road closures or detours in such locations. Mountain passes and tunnels could be closed as a precautionary measure during periods of intense snowfall.

The disruptive weather will likely cause delays and cancellations at airports across the affected region. Authorities will probably suspend port operations temporarily if strong winds trigger hazardous sea conditions, impacting freight and passenger maritime traffic. Flooding/snow will likely block regional rail lines, causing freight and passenger train delays and cancellations.

Disruptions triggered by inclement weather and resultant hazards, such as flooding or avalanches, will likely persist well after conditions have improved - it could take days before any floodwaters recede and/or officials clear debris. Repair or reconstruction efforts may result in residual disruptions if there is severe damage to infrastructure.