The West Coast is bracing for a powerful Pineapple Express, a storm carrying warm, moisture-filled air from near Hawaii, expected to bring heavy, relentless rain.
Northern California, Oregon and Washington could see up to a foot of rainfall in some areas, raising serious concerns over flooding, landslides, and power outages.
Steady rain will focus on higher terrain, especially the Olympic Mountains, Coastal Range, and Cascades, with two to four inches expected, and an AccuWeather Local StormMax™ of 12 inches on windward slopes.
Additional rain on areas already soaked last week increases the risk of mudslides and worsening runoff through midweek.
Western Washington remains on high alert as multiple rivers are already experiencing minor to moderate flooding, with forecasts indicating further rises due to this week's rain.
The National Weather Service (NWS) has issued multiple flood warnings, which will remain in effect at least through December 18.
Residents should avoid flooded roads, low-water crossings, and swift water, as most flood-related deaths occur in vehicles.
AccuWeather Meteorologist Alex Duffus said: 'Several inches of additional rain this week, on top of last week's totals, can lead to renewed major flooding, including on rivers that recently crested at record levels.'
He added that rivers may take several days to crest even after the rain tapers off.
AccuWeather Senior Meteorologist Alex Sosnowski said: 'Expect multiple, rapid rounds of moderate to major flooding of the short-run rivers in the higher and intermediate elevations of the Cascades this week.
'Flooding in the higher elevations can occur in a matter of a few hours. However, where these rivers reach lower, flatter terrain just above sea level, moderate to major flooding can be delayed and longer-lasting and perhaps up to a few days. Multiple crests are likely.'
An atmospheric river is a long, narrow tract of the atmosphere that gathers moisture from the tropics and sweeps it toward the poles.
The Pineapple Express is a well-known example, originating in the tropical Pacific near Hawaii.
Meteorologist Jeff Berardelli of WFLA-TV (Tampa Bay) warned on X that the storm could deliver 'pockets of 12–18 inches of rain and flash flooding' across the West Coast over the next two weeks.
Residents should remain vigilant through the week, as saturated ground and rising rivers will prolong the risk of floods and landslides even after the storm moves on.
From Tuesday night into Wednesday morning, a cooler push of air will also increase the chance for widespread accumulating snow across the region, with snow levels dropping as low as 4,000 feet in places such as Stevens Pass, AccuWeather reported.
The event will begin Monday and continue through Wednesday morning, with additional rain and high-elevation snow possible later in the week.
Steady, intense winds are expected across the Northwest, with coastal gusts up to 50 mph and even stronger gusts inland through the northern Rockies, affecting Washington, Oregon, Idaho, Montana and Wyoming.
Residents in flood-prone areas should remain alert and prepare for potentially severe flooding, while local authorities continue to monitor rivers and issue evacuation orders.
Washington is still reeling from days of torrential rain that triggered historic floods, forcing thousands from their homes and leaving residents stranded on rooftops.
Flood warnings in western Washington have put 100,000 residents in Skagit and Snohomish counties under Level 3 evacuation orders, meaning they were told to 'leave now.'
Governor Bob Ferguson announced that President Trump had authorized FEMA emergency aid, saying he was grateful for the federal support during the ongoing crisis.
Ferguson cautioned residents to follow evacuation instructions closely, noting that rivers such as the Skagit are expected to crest at historic levels midweek.
Several bridges and major roads have been washed out, families have been helicopter-rescued from rooftops, and at least two houses have been ripped from their foundations.
