15 May 2023 | 10:29 AM UTC
New Zealand: Adverse weather forecast over parts of southern and western South Island through at least early May 18
Severe weather forecast over parts of South Island, New Zealand, through at least May 18. Flooding and associated disruptions possible.
Event
Heavy rainfall is forecast over parts of southern and western South Island through at least early May 18. An active weather front is forecast to move over southern and central South Island May 16-17. Heavy downpours may be accompanied by isolated thunderstorm activity and strong wind gusts. Rainfall totals of 9-14 cm (3.5-5.5 inches) are expected in parts of northern Fiordland. Flooding is possible in low-lying areas following periods of intense rainfall, as well as landslides on unstable slopes.
As of late May 15, the Meteorological Service of New Zealand (MetService) has issued the following watches and warnings across the affected area:
Orange Heavy Rain Warning (the middle level on a three-tier scale): Fiordland about and north of Doubtful Sound.
Yellow Heavy Rain Watch: Westland south of Harihari; and Southland north of Gore.
Authorities will likely issue new alerts or update/rescind existing advisories as weather conditions change over the coming days.
Hazardous Conditions
Sustained heavy rainfall could trigger flooding in low-lying communities near rivers, streams, and creeks. Urban flooding is also possible in developed areas with easily overwhelmed or a lack of stormwater drainage systems. Sites located downstream from large reservoirs or rivers may be subject to flash flooding after relatively short periods of intense rainfall. Landslides are possible in hilly or mountainous areas, especially where the soil has become saturated by heavy rainfall. Additional power outages are possible in areas impacted by the weather system.
Transport
Floodwaters and debris flows may render some bridges, rail networks, or roadways impassable, impacting overland travel in and around affected areas. Ponding on road surfaces could cause hazardous driving conditions on regional highways. Authorities could temporarily close some low-lying routes that become inundated by floodwaters. The disruptive weather may cause additional delays and cancellations at regional airports. Flooding could block regional rail lines; freight cancellations are possible in areas subject to heavy rainfall and track blockages.
Disruptions triggered by inclement weather and resultant hazards, such as flooding, could persist well after weather 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 updates and related advisories. Confirm all transport reservations and business appointments before travel. Make allowances for localized travel delays and potential supply chain disruptions where flooding has been forecast or reported. Do not drive on flooded roads. Charge battery-powered devices in the case of prolonged electricity outages.
