Mexico: Adverse weather conditions forecast across much of the country through at least Sept. 27 /update 3

Adverse weather is forecast to continue across much of Mexico through at least Sept. 27. A combination of meteorological phenomena is expected to generate heavy rainfall and thunderstorms across many parts of the country over the coming days. Strong wind gusts, lightning, and hail are possible during storms. Tropical Storm John off the southwest coast is expected to make landfall over Oaxaca Province Sept. 24, bringing heavy rainfall, strong winds, and rough seas to coastal and adjacent inland areas of Chiapas, Guerrero, and Oaxaca states. Another low-pressure area with the potential for cyclonic development off the Yucatan Peninsula will bring heavy rainfall to eastern and southeastern regions. A cold front near the northern border with the US will bring showers, storms, strong winds, and possible hail to northern and northeastern regions over the coming days; strong winds may also generate dust storms in arid areas. Low-pressure channels over western and central Mexico will bring further showers and storms to these regions.

Rainfall totals of over 25 cm (10 inches) are forecast over parts of Guerrero and Oaxaca Sept. 25-26 and Chiapas Sept. 25. Rainfall totals of 15-25 cm (6-10 inches) are expected over parts of Chiapas, Guerrero, and Oaxaca Sept. 23-24, Quintana Roo and Yucatan Setp. 24-25, Campeche and Tabasco Sept. 24, Puebla and Veracruz Sept. 25-26, and Chiapas and Tabasco Sept. 26. Rainfall totals of 5-15 cm (2-6 inches) are forecast across many other parts of the country Sept. 23-26. Winds gusting up to 90 kph (56 mph) and waves up to 4 meters (13 feet) high are expected over the southwestern Pacific coast and the Yucatan Peninsula coast 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 downstream from large reservoirs or rivers may be subject to flash flooding after relatively short periods of intense rainfall. Further landslides are possible in hilly or mountainous areas, especially where heavy rain has saturated the soil.

The severe weather could contribute to transport disruptions throughout affected regions. 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 may also trigger flight delays and cancellations at airports across the affected region. Authorities may temporarily suspend port operations if strong winds trigger hazardous sea conditions, impacting freight and passenger maritime traffic. Flooding could block regional rail lines; freight and passenger train delays and cancellations are likely in areas with heavy rainfall and potential track inundation.