11 Oct 2021 | 02:45 AM UTC
New Zealand: Heavy rainfall and heavy snowfall forecast in western and northeastern regions through at least Oct. 12
Heavy rainfall and heavy snowfall forecast in western and northeastern New Zealand through at least Oct. 12. Disruptions possible.
Event
Heavy rain and snowfall are forecast in portions of western and northeastern New Zealand through at least Oct. 12. The affected areas include eastern Bay of Plenty, western Cantebury, northern Manawatu-Wanganui, far western Otago, western Southland, western Taranaki, western Tasman, and West Coast regions. As of Oct. 11, the New Zealand National Meteorological Service (MetService) has issued the following warnings:
Heavy Rain Warning: The ranges of Westland south of Otira and Fiordland; up to 10 cm (4 inches) of rainfall could occur in these areas.
Heavy Rain Watch: The ranges of Bay of Plenty east of Opotiki, Tongariro National Park, Mount Taranaki, the Tararua Range, the ranges of Tasman west of Motueka, the ranges of Buller, the ranges of Westland about and north of Otira, the headwaters of the Canterbury lakes and rivers south of Arthur's Pass, and the headwaters of the Otago lakes and rivers.
Heavy Snow Watch: Canterbury High Country south of the Rangitata River, Central Otago, and Queenstown Lakes District; snow is forecast to lower to 400 metres (1312 feet) with heavier snow at higher elevations.
Road Snowfall Warnings: Arthur's Pass (SH73), Crown Range Road, Lindis Pass (SH8), Milford Road (SH94), and Porters Pass (SH73).
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 (including rain and snow), 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 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 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. In addition to the snow, strong wind gusts could lead to periods of blowing and drifting snow. Sporadic power outages are possible throughout the affected area.
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. 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. Authorities could temporarily close some low-lying routes that become inundated by floodwaters. The disruptive weather may cause some delays and cancellations at regional airports. Authorities may temporarily suspend port operations along the Bay of Plenty and Tasman Sea if strong winds trigger hazardous sea conditions, impacting freight and passenger maritime traffic. Flooding could block regional rail lines; freight cancellations are possible in areas that see heavy rainfall and potential track blockages.
Disruptions triggered by inclement weather and resultant hazards, such as flooding, 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 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. Stay away from elevated streams, creeks, and other watercourses that are prone to flash flooding. Do not drive on flooded roads. Exercise caution in elevated terrain due to the threat of landslides, as well as mountainous regions where avalanches pose a threat. Charge battery-powered devices in the case of prolonged electricity outages.
