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On October 25, 2021, a phenomenon called an "atmospheric river" is continuing

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to dump heavy rain and mountain snow across the Western U.S. and Canada.

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A previous atmospheric river impacted the West Coast 
about a month earlier in mid-September, 2021.

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Atmospheric rivers are long, narrow belts of moisture that move through the atmosphere.

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They can deliver large amounts of rain and high-elevation snow.

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This deluge of rain can help end droughts, but also produce flash flooding
and mudslides in some areas.

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Approximately 250-375 miles wide on average, atmospheric rivers move with 

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the weather pattern and are present at any time on Earth.

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They are a critical water supply for a portion of the Western U.S., providing 30-50% 
of annual rainfall.

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NOAA satellites monitor these rivers in the sky as they make their way over the West Coast.

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GOES-17 provides detailed information about moisture in the atmosphere

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and allows forecasters to track atmospheric rivers as they happen.

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Satellite imagery can also identify boundaries between different air masses.

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Microwave sounding instruments on the JPSS satellites allow scientists to see through

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the cloud cover and probe the atmosphere vertically, 
to collect data on temperature and moisture.

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The data allows forecaseters to give advanced warnings on heavy rain and snow.

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NOAA satellites provide critical data for forecasting atmospheric weather

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events and monitoring the weather conditions they bring.

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Earth from Orbit: Atmospheric River Hits the West Coast

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Additional imagery courtesy of CIMSS, NASA's SVS, and the NOAA Visualization Lab.

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