Ireland, Northern Ireland: Adverse weather forecast across the region through May 21

Severe weather is forecast across parts of northern and western Ireland and central and western Northern Ireland through May 21. Thunderstorms are expected to movely slowly across the affected area over the coming hours and will be accompanied by heavy downpours, strong wind gusts, lightning, and possible hail are forecast across the region. Heavy rainfall could lead to flooding in low-lying areas and strong winds may cause property damage and power outages.

As of May 20, Met Eireann has issued orange thunderstorm warnings across Donegal, Leitrim, Mayo, and Sligo counties and yellow thunderstorm warnings across Cavan, Connacht, Galway, Longford, and Roscommon counties through late May 20. The UK Met Office issued yellow thunderstorm warnings across western parts of Northern Ireland on May 20 and a separate yellow warning across central and western regions on May 21. Authorities will likely issue new alerts or update/rescind existing advisories as weather conditions change over the coming days.

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 heavy rain has saturated the soil. 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 likely 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 and some employees' inability to reach work sites.