How much rain has Willamette Valley and Oregon Coast seen in December?
It’s been a rain-drenched start to December in western Oregon, and it’s not finished yet.
A parade of atmospheric rivers — systems that pull in heavy amounts of moisture from the Pacific — have been hitting the Pacific Northwest like a firehose.
A total of three of the systems have hit Oregon since Dec. 1, bringing around 5 inches of rainfall in the Willamette Valley and over 6 inches on the Oregon Coast. And it isn't finished yet, as yet another system of heavy rain is forecast for this weekend, with flooding once against possible primarily on the coast.
“As of right now, our models are showing a weak to moderate atmospheric river starting Saturday,” National Weather Service meteorologist Noah Alviz said. “Because this upcoming one is coming more from west than southwest, it could really enhance rainfall in higher terrain in the Coast Range."
Alviz said current estimates show the system bringing 1-2 inches of rain at the coast, 2-4 inches in the Coast Range’s higher elevations and .75-1.25 inches in the Willamette Valley.
Depending on how powerfully the systems arrive, coastal rivers have a 15-30% chance of reaching minor flood stage once again.
“The coast is definitely our biggest concern right now since they just had a strong system go through, already have rivers at or near flood stage and have very saturated soil,” Alviz said.
Concerns aren’t nearly as high about additional flooding in the Willamette Valley. The level of the Willamette River in Salem, for example, has been downgraded to about 18 feet while smaller streams should continue to mostly drop.
Storm damage felt across Northwest
The most recent storm battered the Oregon Coast, bringing about $2.5 million in infrastructure damage to Tillamook County as some roadways were damaged while others were shut down for extended periods.
Deaths and multiple rescues were also reported on the Washington and Oregon coasts.
How much rain has Oregon gotten so far?
December is traditionally Oregon’s wettest month, but even by those standards, the start to the month has been wet.
Salem received 4.98 inches of rain while Eugene had 4.51 inches from Dec. 1 to Thursday. Portland got 5.24 inches, and set a record for rainfall on Wednesday with 1.68 inches. Willamette Valley cities typically average between 6 to 8 inches for the entire month.
On the coast, Astoria has seen 6.5 inches of rain while Tillamook got 6.33 inches. Coastal cities usually average 10-13 inches of rain for the entire month.
What about mountain snow?
A key factor about atmospheric rivers is they are typically warm, and that has meant mostly rain even at mountain pass levels in the Cascade Range.
While the forecast over the next two days is for 10-20 inches of snow in the Cascades, that is forecast to turn to rain by the weekend and melt some or much of the snow that falls.
El Niño to blame?
While it’s too early to say for certain what type of winter Oregon will continue to have, the two scenarios for this winter are playing out pretty much as expected. El Niño winters favor warmer than normal conditions across the board. The strength of this year’s El Niño could bring either wetter or drier than normal conditions, depending on how warm the Pacific Ocean gets.
Zach Urness has been an outdoors reporter in Oregon for 15 years and is host of the Explore Oregon Podcast. Urness is the author of “Best Hikes with Kids: Oregon” and “Hiking Southern Oregon.” He can be reached at zurness@StatesmanJournal.com or (503) 399-6801. Find him on Twitter at @ZachsORoutdoors.
This article originally appeared on Salem Statesman Journal: Oregon to see fourth atmospheric river, December rain totals
