'Atmospheric river' expected to dump 2 inches of rain on Seattle, cause flooding on roads

An atmospheric river is expected to dump as much as two inches of rain on Seattle over the next day, and the National Weather Service (NWS) in Seattle said drivers can expect slightly hazardous road conditions as water collects on city streets.

The weather equivalent of a fire hose, an atmospheric river is a concentrated corridor of moisture that shoots wetness into an area for an extended period of time. Samantha Borth, a forecaster with NWS in Seattle, said gutters and drains clogged with fallen leaves will likely cause water to pool on roadways.

“If you’re going out driving, take it slower,” Borth said. “A lot of leaves are still in gutters, and that helps create ponding on the roadways.”

NWS expects the heavy rainfall to let up slightly Friday morning, but said it likely won’t stop until Saturday. There’s also a chance that the atmospheric river could stall when trying to move out of the area, which means we could see similar periods of rain through Sunday.

Seattle and Everett will likely see 1.5 to 2 inches, while 2 to 3 inches are expected farther south in Tacoma, Olympia and Shelton. Moderate river flooding is also expected throughout the region and will recede over the weekend. A flood watch is in effect from 4 p.m. this afternoon through Saturday afternoon for much of the region.

Thunderstorms, strong winds and flashes of lightening are likely on the Olympic Peninsula and lower Seattle metro area through Thursday according to NWS. Snow levels in the Cascade Mountains will rise rapidly over Thursday and will be at the 9,000-foot level by Thursday night.