In brief
The Pacific Northwest is bracing for a powerful "bomb cyclone," projected to bring severe weather conditions including heavy snowfall, high winds, and potential flooding. The storm is expected to severely impact travel and cause power outages across several states.
A major "bomb cyclone" developing off the US Northwest coast is poised to bring intense weather conditions, including rain, snow, and high winds, to over seven million residents living along the Pacific coast. The storm began influencing the region on Tuesday and is projected to gain strength, with increasingly hazardous weather anticipated through the end of the week, according to the National Oceanic and Atmospheric Administration (NOAA).In addition to strong winds and precipitation, residents may experience flash floods, rockslides, and debris flows, as well as exhaustive mountain snow and blizzard-like conditions in elevated areas. This rapidly intensifying storm system results from a significant drop in air pressure, a phenomenon described by meteorologists as a "bomb cyclone."Parts of the Pacific Northwest are already experiencing the initial effects, with robust wind gusts recorded in the Seattle area. NOAA forecasts that mountain ranges will endure heavy, wet snow with accumulation rates as high as 2-3 inches (5-8 cm) per hour and winds reaching up to 65 mph (29 mps). The agency warns that extremely poor visibility due to whiteout conditions could make travel treacherous.Expectations of snowfall range from 10-20 inches (25-50 cm) in certain locations. In addition to the potential for power outages and downed trees due to wind gusts, the NOAA has indicated heightened risk for coastal areas as a "high risk excessive rainfall outlook" has been issued for northwestern California.The forecast predicts that the heaviest rainfall, bringing the risk of mudslides, will occur in northern California and southwest Oregon. The National Weather Service has also announced winter weather alerts and a winter storm warning for several areas along the Pacific coast. As this storm reaches its peak intensity, widespread flash flooding, hazardous travel conditions, power outages, and tree damage are anticipated.The term "bomb cyclone" refers to storms that experience rapid intensification, with a central air pressure decline of at least 24 millibars within 24 hours. These storms are notorious for their explosive power and can result in various severe weather phenomena, from blizzards to intense thunderstorms and heavy rainfall.Forecaster Helen Rossington from BBC Weather explains that the bomb cyclone is expected to first deliver strong winds, rain, and snow to the northwest coast before unleashing prolonged periods of significant rain, mountain snow, and flood risks in the subsequent days. While these weather events are typical for this seasonal period, the combination of an atmospheric river with a bomb cyclone can signify a major meteorological event for the region.
