Atmospheric rivers are huge bands of warm, moist tropical air that provide much of the precipitation in the western U.S. and are most common from fall through spring. While an essential source of water, the most powerful of these storms also pose severe flood risks.
The past year brought a series of severe atmospheric river events to the western United States. Use these talking points to inform your clients of the risk atmospheric rivers can bring to their area:
- In mid-January 2021, a category 5 (the most severe storm) atmospheric river brought flooding to parts of western Washington and northwest Oregon, with a second heavy pulse in southwest Oregon and northwest California.
- In late January 2021, an atmospheric river brought drenching rains to southern California and blizzard conditions in the Sierra Nevada Mountains. Central California was hit hardest, with severe 24-hour rainfalls that washed out a 150-foot section of Highway 1 in Big Sur. The storm poured 14 inches of rain on San Luis Obispo and forced evacuations in the foothill neighborhoods below the El Dorado Fire burn scar.
- On October 23-27, 2021, another category 5 storm swept through California, dropping an estimated 7.6 trillion gallons of rain. While this atmospheric river helped douse wildfires, it also caused mudslides that closed roads in the San Bernardino Mountains, dropped 4 inches on downtown San Francisco in one day, and 5.44 inches on Sacramento, shattering one-day rainfall records that stood since 1880. The storm went on to slam Oregon and Washington.
- October 29-November 3, 2021, brought an atmospheric storm to southern Alaska, with the Portage Glacier Visitors Center receiving a record-breaking 22.35 inches over 3 days. The storm caused flooding in Girdwood and a landslide that closed the Sterling Highway.
- On November 14, 2021, atmospheric river-driven flooding and landslides closed Interstate 5, the West Coast’s main north-south highway, near Bellingham, Washington, forcing school closures and evacuations in multiple areas. The Governor declared a severe weather state of emergency in 14 western Washington counties
While some forecasters expect precipitation in California to be lower than normal for winter 2021-22, it’s important to remember that weather is increasingly unpredictable and severe. Buying and maintaining flood insurance is the best way for your clients to protect the lives they’ve built. Remember—anywhere (and any time) it can rain, it can flood!
You can explore more atmospheric river information in this article.