US: Adverse weather forecast across northwestern regions through at least early Jan. 14

Event

Rounds of heavy rainfall, strong winds, and possible flooding associated with a low-pressure system are forecast to occur across portions of the northwestern US through at least early Jan. 14. The affected area includes far northwestern California, western Oregon, and western Washington. The Weather Prediction Center (WPC) has issued a "Moderate Risk" for excessive rainfall for coastal northwestern Oregon and a "Slight Risk" for excessive rainfall for far northwestern California, western Oregon, and western Washington, where the heaviest rainfall is forecast. Additionally, the National Weather Service (NWS) has issued flood watches for portions of western Oregon and western Washington. Officials could update and possibly extend the coverage of the relevant weather alerts over the coming days.

Hazardous Conditions
The storms will be capable of producing heavy downpours and damaging winds across the affected area through at least early Jan. 14. Should sustained heavy rainfall occur, it 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 the soil has become saturated by heavy rainfall. Disruptions to electricity and telecommunications services are possible where significant flooding, landslides, or strong winds impact utility networks.

Transport
Floodwaters and debris flows could render some bridges, rail networks, or roadways impassable, impacting overland travel 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 intermittent flight delays and cancellations at regional airports, though these are unlikely to be severe or prolonged. Flooding could block regional rail lines; freight and passenger train delays and cancellations are likely in areas that see heavy rainfall and potential track inundation. Localized business disruptions may occur in low-lying areas.

Advice

Monitor local media for weather updates and related advisories. Confirm all transport reservations and business appointments before travel. Make allowances for localized travel delays and potential supply chain disruptions where flooding has been forecast. Do not drive on flooded roads. Charge battery-powered devices in the case of prolonged electricity outages.

Resources

US National Weather Service (NWS)
US Road Conditions