US: Adverse weather forecast across southern and southeastern regions through at least early Jan. 27 /update 1

Severe weather is forecast across parts of the southern and southeastern US through at least early Jan. 27. A low-pressure system will combine with moisture drawn in from the Gulf of Mexico to bring several rounds of heavy rainfall across the Lower Mississippi Valley, Tennessee Valley, and the Gulf States over the coming days. Rainfall totals of more than 10 cm (4 inches) are possible across parts of the region through early Jan. 27. Storms may accompany the heavy downpours at times.

As of early Jan. 24, the US National Weather Service (NWS) has issued flood warnings, watches, and advisories across much of the affected area. Flash flood warnings are also in place for parts of southeastern and eastern Texas and southwestern Louisiana. The NWS's Weather Prediction Center has forecast a moderate risk of excessive rainfall (the second highest level on a four-tier scale) for parts of eastern Texas, southern Arkansas, and northwestern Louisana and a slight risk of excessive rainfall for surrounding areas of eastern Texas, southeastern Oklahoma, Arkansas, Louisiana, and western Mississippi Jan. 24. There is a further moderate risk of excessive rainfall for parts of far eastern Texas, central and southern Louisiana, and western Mississippi and a slight risk for surrounding areas of eastern Texas, southeastern Arkansas, Louisiana, Mississippi, northern and western Alabama, and southern Tennessee late Jan. 24-early Jan. 25. A slight risk of excessive rainfall continues over central and eastern parts of the affected area through early Jan. 27. The NWS's Storm Prediction Center has warned of a slight risk of severe thunderstorms (the second lowest level on a five-tier scale) for parts of southern Louisiana and southwestern Mississippi overnight Jan. 24-25; tornadoes are possible in the affected area. 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 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.

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 or landslides impact utility networks.

The severe weather will likely contribute to transport disruptions throughout the region. 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 will probably temporarily close low-lying routes that become inundated by floodwaters.

Severe weather will likely cause flight delays and cancellations at airports across the affected region. Flooding could block regional rail lines; freight and passenger train delays and cancellations are probable in areas with heavy rainfall and potential track inundation.

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