Forecasters say the storms will bring rain, snow, and then more rain to millions in the western U.S. in the coming days, marking a slow start to December.
When the rainy season comes to the Pacific Northwest, “sometimes it doesn't go away,” said AccuWeather meteorologist Kevin Coskeren, referring to the days of rain expected in Seattle next week.
Seattle, Tacoma and Olympia, Washington, will be under a flood watch starting Sunday morning, the National Weather Service said, as the region braces for heavy rain and snow, bringing damaging wind gusts and widespread river flooding.
The East Coast will also see a wet weekend, along with about 10 states, from Maryland to Maine, the National Weather Service said Saturday. It is expected to get rain. Residents along the Gulf Coast are also bracing for severe thunderstorms this week, which could reach… Four inches of rain.
Saturday morning's storms have already knocked out power in parts of Seattle, the National Weather Service said on X, previously Twitter.
Winter storm warnings were issued around Salt Lake City Saturday morning, ahead of widespread snow storms expected Saturday afternoon and Sunday morning.
Up to three feet of snow could fall in Colorado, Idaho, Utah and Wyoming in some areas in the coming days, causing serious transportation disruptions, the National Weather Service said Saturday.
What is an atmospheric river?They bring near-constant rain to the western United States
The atmospheric river brings rain and snow
This week's heavy rainfall in the West is the result of an atmospheric river, an influx of moisture from the Pacific Ocean that provides near-constant rain on the West Coast of the United States.
Ribbons of water vapor, visible from clouds, extend thousands of miles from the tropics to California, Oregon and Washington. They are 250 to 375 miles wide, and provide fuel for heavy rains and snowstorms.
In general, atmospheric rivers capture water vapor from warm, moist air in tropical regions and then drop the water to the ground in cold regions as rain or snow.
Monthly rainfall in the Pacific Northwest
By the middle of next week, Portland could receive about six inches of rain, representing the city's typical totals for December, according to AccuWeather. The National Weather Service expects up to 10 inches of rain to fall on the Oregon coast in the coming days.
“These will be some submarines,” Coskren said, describing the atmospheric river as “open for business.”
The National Weather Service in Portland said runoff from melting snow combined with heavy rain on Sunday and Monday will increase the risk of flooding, with low-lying areas and urban areas with poor drainage particularly at risk of pooling water.
High winds could reach 40 mph in Portland, reducing visibility for motorists, the National Weather Service said Friday.
Snow can make travel impossible in the Rocky Mountains
Residents in the western United States are bracing for a second round of snow on Saturday, the National Weather Service in Boise said, after blizzards swept through the region on Friday, reducing visibility on roads.
Mount St. Helens, Wash., had already received nine inches of snow by Friday, and towns in Oregon, including Hood River, weren't far behind — totaling six inches of snowfall before the weekend, AccuWeather reported.
Parts of the Rocky Mountains could receive up to three feet of snow through Sunday, “potentially creating dangerous and even impossible travel conditions,” the National Weather Service said Saturday.
“Life-threatening travel conditions” will develop across wide swaths of Washington, Oregon and Idaho due to heavy snowfall, Coskeren said.
Humid winter weather in the northeast of the country
On Sunday, the I-95 corridor could be drenched in rain, and farther north in New England, the rain will turn to snow Sunday night, according to the National Weather Service forecast.
Heavy snow is expected in parts of New Hampshire, Vermont and Maine, with more than six inches possible on Sunday, the weather service said Saturday.
Thunderstorms on the Gulf Coast
A low pressure system mixing with moisture from the Gulf of Mexico is expected to ignite thunderstorms from Louisiana to the Florida Panhandle over the next few days, according to the National Weather Service, bringing 1 to 4 inches of rain in some areas.
The weather service says damaging wind gusts and tornadoes are possible.
Contributing: Doyle Rice, USA TODAY