The strong low-pressure system responsible for much of the extreme weather traversed much of the Pacific Ocean, before the first storm arrived late on January 3.On December 29, 2007, a powerful extratropical disturbance developed over eastern Siberia, which emerged into the northwest Pacific, and moved to the Aleutian Islands as a well-defined low by January 3.On January 2, another extratropical disturbance developed within a well-defined trough of low pressure, in the northeast Pacific Ocean.[8] On January 3, the 1st storm system approached the northern part of the West Coast, powered by a Pineapple Express atmospheric river, resulting in heavy downpours of rain and strong gusts across much of the Western Seaboard.[14] The highest reported wind gusts were 165 mph (266 km/h) in Tahoe City, California, equivalent to a Category 5 hurricane on the Saffir- Simpson scale.Soon afterwards, a few clumps of the mass of moisture organized into separate storm systems,[20] while the dominant low over Canada stalled just southwest of Hudson Bay.On January 10, the low west of Hudson Bay dissipated, while the main storm complex began to exit Atlantic Canada.[1] Flights departing from San Francisco were grounded, while over 100 miles (160 km) of Interstate 80 was shut down in eastern California and western Nevada due to poor visibility and a 17-vehicle pile-up.Bay Area Rapid Transit was also disrupted with significant delays to service and was even interrupted between San Francisco and Daly City briefly due to fallen trees on the network's tracks.At least 12 people were killed including two in California, eight in Utah and two in Oregon due to falling branches or trees, traffic accidents, and flooding.