Atmospheric River Prompts Winter Storm Warnings Across 11 US States

An atmospheric river is a narrow space that transports water vapor.

Atmospheric rivers have been lashing the Pacific Northwest of the United States, prompting winter storm warnings across 11 US states, which predicted more heavy rain, snow, and strong winds in the coming days.

According to the National Oceanic and Atmospheric Administration, an atmospheric river is a narrow space in the atmosphere that transports significant amounts of water vapor. When they hit land, the vapor was released through rain or snow.

Atmospheric Rivers Prompt Winter Storm Warnings

DENMARK-WEATHER-SNOW
A snow covered street is pictured in Svennerup, Zealand, Denmark, on November, 30, 2023. MADS CLAUS RASMUSSEN/Ritzau Scanpix/AFP via Getty Images

AccuWeather meteorologist Alyssa Glenny predicted that places across Washington, Oregon, Northwest California, northern Idaho, and western Montana could experience even more wild weather from Sunday to Wednesday due to an atmospheric river overhead.

According to Newsweek, the warnings are currently in effect for parts of Colorado, Idaho, Maine, Nevada, New Hampshire, New York, Oregon, Utah, Vermont, Washington, and Wyoming.

Glenny reported that there would be an additional 1-2 inches of rain in most affected regions. Coastal areas were expected to be hit with far more rain, with 4-8 inches of rain.

Regions from northwest California to western Washington have reported flooded roadways and travel disruptions with rock and mudslides. Furthermore, there would also be additional rainfall in those areas that could worsen the conditions.

Flood watches and advisories were announced for numerous counties across western Washington and Oregon through Wednesday night due to the steady stream of rainfall that will continue to spread inland.

According to the December 4 report, Glenny warned the highest population centers of the Pacific Northwest, Seattle, Portland, and Oregon, as they could potentially see a total of a month's rainfall in the first six days of December as the prolonged stretch of rain continues.

"As of Sunday evening, 1.25 inches has fallen in Seattle since the start of the month, while Portland has recorded 2.20 inches," AccuWeather meteorologist Elizabeth Danco said.

She added that both cities were expected to receive an additional 2-4 inches of rain through Wednesday, and the historical average rainfall for December is 5.72 inches in Seattle and 5.77 inches in Portland.

AccuWeather Meteorologist Haley Taylor believed the heaviest rain would occur by Wednesday, leaving a lingering moist condition by Thursday night. She said dry conditions were expected to continue on Friday, but another round of rain and mountain snow could sneak back into the Pacific Northwest by late Friday into Saturday.

California Drought-Free

California has been struggling with atmospheric river floods from November to January. In March, most of California would encounter another atmospheric river storm system that would likely produce heavy rain.

Atmospheric rivers flowed into California in September, triggering warnings of widespread heavy rain and flooding on several major highways and small rural communities in the southern and central regions of the state.

The heavy rain and flood resulted in over 9,000 people evacuating and over 54,000 without power, as parts of California were struck with another atmospheric river system.

California has been facing a prolonged drought for nearly three years during an extensive La Nina event. However, after a shift toward neutral and El Nino conditions, the state has been declared officially drought-free until the end of January 2024.

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