18 Jul 2023 | 11:50 PM UTC
New Zealand: Heavy snowfall and rainfall forecast across southern South Island through at least July 20
Heavy snowfall and rainfall forecast in southern South Island, New Zealand, through July 20. Transport disruptions possible.
Event
Heavy snowfall and rainfall are forecast in southern South Island through at least July 20. The New Zealand National Meteorological Service (MetService) warned that a front associated with a low pressure system over the Tasman Sea is likely to track slowly northwards over southern New Zealand through early July 20 before moving offshore to the west, bringing the snow level down to around 300 meters (984 feet) in parts of Canterbury, Otago, and Southland.
Heavy snow may disrupt travel and could damage trees and powerlines, while cold conditions may cause stress for livestock. As of early July 19, the MetService has issued the following weather warnings:
Orange (middle level on a three-tier scale) Heavy Snow Warning: Queenstown Lakes and Central Otago. 15-25 cm (6-10 inches) of snow is forecast at elevations above 600 meters (1,968 feet), with lesser amounts down to 300 meters (984 feet).
Yellow Heavy Snow Watch: Canterbury High Country south of Lake Tekapo.
Yellow Heavy Rain Watch: Fiordland and Westland south of the glaciers.
Road Snowfall Warning: Haast Pass (SH6), Lindis Pass (SH8), Milford Road (SH94), and Crown Range Road.
Authorities will likely issue new alerts or update/rescind existing advisories as weather conditions change over the coming days.
Hazardous Conditions
The storm could produce rounds of heavy precipitation, strong winds, and isolated thunderstorm activity. Where precipitation falls as rain, flash and areal flooding is possible. Such flooding is possible in low-lying communities near watercourses and other large bodies of water, as well as in urban areas with easily overwhelmed stormwater drainage systems. Sites located downstream of large reservoirs may be subject to flash flooding after relatively short periods of intense rainfall.
Precipitation could fall as snow in higher elevations over the coming days. Wind gusts could cause blowing and drifting snow; decreased visibility is likely in mountainous areas. Rain-induced landslides cannot be discounted 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 could occur throughout the affected area.
Transport
Floodwaters and related debris may render some bridges, rail networks, or roadways impassable, impacting overland travel in and around the affected area. Flooding in urban areas could also result in significant traffic congestion. Heavy snow will likely make driving hazardous in some areas; authorities could 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 some delays and cancellations at airports across the affected region. Authorities may temporarily suspend port operations if strong winds trigger hazardous sea conditions, impacting freight and passenger maritime traffic. Flooding/snow could block regional rail lines; freight and passenger train delays and cancellations are possible in areas that see heavy rainfall and potential track blockages.
Disruptions triggered by inclement weather and resultant hazards, such as flooding or avalanches, could persist well after conditions have improved - it could take days before any floodwaters recede and/or officials clear debris. If there is severe damage to infrastructure, repair or reconstruction efforts may result in residual disruptions.
Advice
Monitor local media for weather-related updates and advisories. Seek updated information on road conditions before driving or routing shipments through areas where severe weather is forecast; plan for possible delivery delays throughout the affected area. Allow extra time to reach destinations and carry an emergency kit and warm clothes if driving is necessary, especially on secondary or rural routes that could become impassable. Charge battery-powered devices in the case of prolonged electricity outages.
