October 19, 2021

Multiple Rounds Of Heavy Rain Heading For The West Coast Through Early Next Week

An active pattern will send multiple waves of drenching rain into the West Coast this week, bringing measurable rainfall from the central California coast straight up through coastal British Columbia. The heaviest rain will fall at higher elevations—with heavy mountain snow likely in California—but just about everyone from Santa Barbara to Seattle has some much-needed rain on the way.

The impending bouts of heavy rain will be the result of several atmospheric rivers, or bands of enhanced upper-level moisture that flow from the tropics to the mid-latitudes. Atmospheric rivers act like reservoirs that can boost rainfall rates.

The latest 7-day precipitation forecast from the Weather Prediction Center shows 5+ inches of rain falling across a huge portion of the West Coast. As usual, higher terrain near the water will see higher totals, while cities at lower elevations or in rain shadows will see lower rainfall amounts. High elevations are going to get thumped with a decent amount of snow by this time next week.

This is going to be a long-duration event with the potential for three or four rounds of precipitation through early next week.

The first wave of precipitation is arriving in northern California this evening, and it'll sweep through the Pacific Northwest throughout the day on Wednesday. The second round, associated with a front extending off a low heading into British Columbia, will arrive overnight Thursday and taper off through Saturday. A third big wave of precipitation, which is likely going to be the most significant of the bunch, will hit on Sunday and last through early next week.

Make sure wireless emergency alerts are activated on your smart phone in case flash flood warnings or evacuation orders are issued for your location. Stay mindful of the threat for landslides and mudslides. If you come upon a flooded roadway, it's not worth trying to drive across. It's impossible to tell how deep the water is before it's too late, and it only takes a few inches of moving water to lift up a vehicle and carry it downstream.

A couple of crummy days on the West Coast are certainly more than worth it after such a hot and dry summer. 

A huge swath of the western United States remains mired in a significant drought. Last week's update of the U.S. Drought Monitor found that 87.18% of the entire state of California in an extreme or exceptional drought, the two highest categories on the scale. The impending rains and mountain snow will bring some beneficial relief to these areas. It won't erase the drought or undo the damage, but anything helps.

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I graduated from the University of South Alabama in 2014 with a degree in political science and a minor in meteorology. I contribute to The Weather Network as a digital writer, and I've written for Forbes, the Washington Post's Capital Weather Gang, Popular Science, Mental Floss, and Gawker's The Vane. My latest book, The Skies Above, is now available. My first book, The Extreme Weather Survival Manual, arrived in October 2015.