Philippines: Adverse weather forecast across northern regions through at least Dec. 6 /update 3

Severe weather is forecast across parts of the northern Philippines through at least Dec. 6. Heavy rainfall and thunderstorms are expected across parts of Cagayan Valley, Cordillera Administrative Region, and Ilocos regions due to a stationary weather front known as a Shear Line over the region; flash flooding and landslides are possible in affected areas. As of Dec. 4, the Philippine Atmospheric, Geophysical, and Astronomical Administration (PAGASA) has issued a weather advisory for heavy rainfall over parts of the affected area. Heavy to intense rainfall of 10-20 cm (4-8 inches) is forecast over Cagayan province Dec. 4-5 and lesser rainfall totals of 5-10 cm (2-4 inches) are forecast across Apayao and Kalinga provinces Dec. 4-5 and Cagayan Province Dec. 5-6. PAGASA has issued severe general flood advisories (the second-lowest level on a four-tier scale) across Cagayan and Isabela provinces in Cagayan Valley Region and Abra, Apayao, Benguet, Ifugao, Kalinga, and Mountain provinces in Cordillera Administrative Region. Moderate general flood advisories are in place for Ilocos Norte, Ilocos Sur, La Union, and Pangasinan provinces in Ilocos Region. Officials could update and extend the coverage of weather alerts over the coming days.

Much of the Philippines is still recovering from severe flooding and landslides brought about by the succession of tropical systems moving across the region over recent weeks. Northern and central regions were the worst affected; however, records indicate the storms impacted 17 of the country's 18 regions. Six storm systems made landfall or passed close to the country since Oct. 24: Tropical Storm Trami (named Kristine in the Philippines) made landfall in Divilacan Town, Isabela Province, at around 00:30 Oct. 24; Tropical Storm Kong-rey (named Leon in the Philippines) made a close approach to northeastern Luzon Oct. 30-31; Tropical Storm Yinxing (named Marce in the Philippines) passed over the north coast of Luzon Nov. 7; Typhoon Toraji (named Nika in the Philippines) made landfall near Dilasag in Aurora Province early Nov. 11; Typhoon Usagi (named Ofel in the Philippines) passed over far northeastern Luzon and past the northern island regions of the Philippines Nov. 14; and finally Super Typhoon Man-yi (name Pepito in the Philippines) made landfall over Catanduanes Island late Nov. 16 and Dipaculao in Aurora Province the afternoon of Nov. 17. Further rainfall could lead to additional flooding and landslides as well as exacerbate the situation and hamper recovery efforts.

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. Landslides are possible in hilly or mountainous areas, especially where heavy rain has saturated the soil.

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.

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, possible evacuations, and some employees' inability to reach work sites.