Springtime Flooding for Western Oregon

With all of the heavy rain we saw over the weekend, many rivers throughout Western Oregon have reached flood stage and are continuing to rise. Here in Portland, I’ve never seen the Willamette as high, muddy, and debris-filled as it is now.

Muddy Willamette River
A view of the Willamette River and Moda Center at 10am between the Broadway and Steel Bridges in Portland. This picture was taken around 10AM, the river has only become dirtier since.

Right now, minor or moderate flooding is occurring on the Siuslaw, Coast Fork of the Willamette, Long Tom, Mohawk, Coquille, and Rogue Rivers, as well as a myriad of small streams in the Southern Valley. Many additional rivers are at or forecast to reach “bankfull” status, which is just below flood stage.

Rivers at or near flood stage
Current flood status of rivers around the Pacific Northwest.
Credit: Northwest River Forecast Center

All of this rain occurred courtesy of an atmospheric river that stalled over the area throughout the weekend and pumped ample subtropical moisture into Oregon and Northern California. Over the past 72 hours, the Portland metro has seen approximately 1.5-2 inches of rain, while locations between Corvallis and Eugene have seen 4+ inches. The Yellowstone Mountain RAWS station at 3,080 feet in the Central Oregon Cascades is the winner thus far, with 8.64 inches since Friday morning!

72-hour rainfall
72-hour-precipitation ending 10:40 AM PDT 4/8/2019
Credit: NWS

For those sick and tired of the rain, I’ve got some bad news. Unseasonably cool and wet weather is expected to persist for the next two weeks, with moderate-strong systems expected Wednesday night/Thursday, Saturday, and potentially Monday, though confidence is low that far out. While these systems are not expected to be as strong as the atmospheric river we saw over the weekend and are not expected to cause any additional flooding, they will keep streamflows high, particularly for lower-elevation rivers west of the Cascades.

Total 16-day (384 hour) precipitation from this morning’s 06Z GFS model
850 hPa (~5000 feet) temperature and 6-hour precipitation from this morning’s 06Z GFS ensembles.

If there is a silver lining, it is that these storms will drop substantial amounts of late-season snowfall throughout the Cascades and Intermountain West. Take a look at the 180-hour accumulated snowfall beginning 5 am this morning from the UW WRF-GFS model. It’s not a blizzard by any stretch, but it’s pretty darn good for April!

Credit: University of Washington Atmospheric Sciences Department

I’m not a good enough forecaster to know what kind of weather we’ll see in May, but I do know that April showers = May flowers, so there’s that to look forward to. 🙂

Thanks for reading and have a great week!
Charlie

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2 Comments

  1. After such a dry March, in the first 7 days my April total has already surpassed last month’s! It’ll be interesting to see how much snow the Cascades can get during these next 14 days – the models are certainly piling it on. Many reservoirs are nearing capacity with this past week’s heavy rains, especially in the central and southern Willamette Valley. Lowering snow levels should mitigate further flooding that’s currently occurring. Time release is good!

    And, you know what Mayflowers bring? Pilgrims.

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