Tacoma, say goodbye to sunshine, hello to ‘atmospheric river’ bringing heavier rain
We regret to report that sunshine is largely bidding us farewell. The fall season has arrived in Tacoma, and a familiar old rascal, an atmospheric river, is greeting us with heavier rain and gusty wind.
That’s according to the National Weather Service, which shows wet weather in the forecast through Friday. Meteorologist Maddie Kristell said the heaviest precipitation is expected Sunday afternoon to early Tuesday morning, with an inch to an inch-and-a-half of rain probably coming to the Tacoma area. Kristell said this weather event will likely mark the end of fire season in Western Washington, as cooler temperatures and better chances of rain become the norm.
Winds will also strengthen Sunday night and remain breezy through Monday, but the strongest winds are likely along the coast. The NWS warned this could cause localized power outages and tree limb damage.
After months of mostly dry weather, Kristell said the abrupt change means roads could be slicker from built-up oil, and any fallen leaves or debris that hasn’t been washed away over the summer could block storm drains, causing some nuisance flooding on sidewalks and roadways.
Rivers are expected to rise, but the weather service said river flooding isn’t expected. However, the risk can’t be ruled out, and rivers’ response to rainfall will be monitored. Since it’s the first significant rainfall of the season, debris flows are possible across recent burn scars if precipitation is high enough.
The meeting of a deeper center of low pressure out of the Gulf of Alaska and a subtropical moisture plume is bringing that increased moisture, according to Kristell, in the form of an atmospheric river.
“It’s this larger area of increased moisture that kind of comes along with the storm track,” the meteorologist said. “And they can be more prolonged rain events just because there’s simply so much moisture coming with them.”
Sometimes described as “rivers in the sky,” atmospheric rivers can vary in size and strength, but according to the National Oceanic and Atmospheric Administration, an average one carries water vapor roughly equivalent to the average flow of water at the mouth of the Mississippi River. Particularly strong ones can transport up to 15 times that amount.
Below-normal temperatures and rounds of rain are likely to continue across the Puget Sound region Wednesday through Friday, but rainfall amounts are so far not expected to have significant effects. Low temperatures are predicted to stay in the mid-50s and high temperatures might inch above 60 degrees.
This story was originally published September 23, 2023 at 11:12 AM.
