Atmospheric River Pummeling Northern California With Flooding Rain, Mudslide, Rockslide Threats

Atmospheric River Pummeling Northern California With Flooding Rain, Mudslide, Rockslide Threats

Chris Dolce

At a Glance

• An atmsopheric river will continue to pummel parts of the West on Friday.
• Heavy rain could trigger flooding, mudslides and rockslides, especially in Northern California and southwest Oregon.
• This wet pattern was kicked off by a 'bomb cyclone' that brought damaging winds to the Northwest.

Latest Status

T​his wet pattern was kicked off by a "bomb cyclone" that brought damaging winds to the Northwest, especially Washington, late Tuesday. See the bottom of this article for a recap on that chapter of the storm.

The biggest concern now is a potent atmospheric river of moisture that has already soaked Northern California the last couple of days. This band of moisture, which has been reinforced by a second offshore storm, is expected to produce heavy rain and mountain snow through Friday night, with the worst impacts affecting Northern California and southwest Oregon. 

Y​ou can see where the rain and mountain snow is ongoing in the West right now in the radar snapshot below. The heaviest precipitation is located in Northern California, and that will persist through Friday.

Some areas of Northern California have picked up over 10 inches of rain since this siege began. The Sonoma County Airport in Santa Rosa had its wettest day in 26 years Wednesday, tallying almost 7 inches of rain.

In all, there have been more than 100 reports of flooding, landslides and rockslides across Northern California in the 48 hours ending Friday morning, according to National Weather Service storm reports. The blue icons plotted on the map of estimated rainfall below show where those reports are located in Northern California.

The highest rainfall totals through the end of Friday will be in Northern California (mainly north of the Bay Area and Sacramento) into southwest Oregon. Storm total rainfall, including what has already fallen, could be 12 to 16 inches in some locations, according to NOAA's Weather Prediction Center. 

Keep in mind the map below shows the rainfall to expect in addition to what has already fallen and not storm totals.

The heavy rain will result in flooding for poor drainage areas as well as creeks and rivers. Mudslides will be an increasing threat too, especially in any recent wildfire burn areas. Rockslides are also possible along some mountain roads.

Elsewhere, lighter amounts of additional rain can be expected in western Oregon and western Washington going forward, with the heaviest amounts in coastal and foothill locations.

Additional systems this weekend into early next week will keep the West Coast unsettled with periods of rain and mountain snow. Winter storm warnings are in effect for parts of California's Sierra Nevada into early next week where snow totals will be measured in feet.

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