South Africa, Eswatini: Adverse weather forecast over parts of eastern South Africa and across Eswatini through at least Dec. 19

Severe weather is forecast across parts of eastern South Africa and across Eswatini through at least Dec. 19. Thunderstorms are forecast across the region and may be accompanied by heavy rainfall, strong winds, lightning, hail, and possible tornadoes. Heavy downpours may trigger flooding in low-lying areas and landslides on unstable slopes. Strong winds may cause property damage and power outages.

The South African Weather Service has issued orange level 5 (out of ten) severe thunderstorm warnings across parts of southern Mpumalanga Province and yellow level 2 severe thunderstorm warnings across the rest of the affected area Dec. 17.

The Estwatini Meteorological Service has issued an advisory for severe thunderstorms across the country Dec. 17. There is a severe risk (the highest level on a three-tier scale) of storms across eastern and southern parts of Eswatini and a moderate risk of storms across the rest of the country.

Further showers and storms are forecast across the region Dec. 18-19 and officials could update and possibly extend the coverage of weather alerts over the coming day.

Sustained heavy rainfall could trigger further flooding in low-lying communities near rivers, streams, and creeks. Urban flooding is also possible in developed areas with easily overwhelmed 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 heavy rain has saturated the soil. Strong winds could create conditions conducive to wildfire development and growth.

Authorities could issue mandatory evacuation orders for flood-prone communities over the coming days. Disruptions to electricity and telecommunications services are possible where significant flooding, strong winds, or landslides impact utility networks.

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.

Severe weather could also trigger flight delays and cancellations at regional airports. Flooding could block regional rail lines; freight and passenger train delays and cancellations are possible in areas with heavy rainfall and potential track inundation.

Localized business disruptions may occur in low-lying areas; some businesses might not operate at full capacity because of flood damage to facilities, possible evacuations, and some employees' inability to reach work sites.