Atmospheric River, Flood Watches & Snow: Puget Sound Forecast

SEATTLE — Western Washington will see impacts from the season's first moderate-to-strong atmospheric river through Saturday, bringing a few rivers into flood stages amid periods of heavy rain and gusty winds. After that, forecasters are tracking a colder shift that could bring an early taste of snow to lower elevati0ns.

The Seattle area may benefit from a rain shadow, and the latest forecasts show lower precipitation totals than earlier models for the Emerald City. However, places like Everett and Tacoma could pick up 2 inches of rain by Saturday evening, with up to four inches possible around Olympia and North Bend.

"Friday through early Saturday will feature the heaviest rainfall," NWS Seattle wrote Thursday. "Several inches of rain are expected along the coast and central Cascades as a warm front drapes itself from west to east over western Washington. Heavy rain is expected to taper off into Saturday morning, but the westerly push associated with the cold front arriving Friday evening may invigorate a convergence zone along the King/Snohomish County border Saturday afternoon."

The potential for flooding remains along area rivers, low-lying areas, and places with poor drainage. A flood watch will be in place across the region through Saturday afternoon, along with flash flood concerns near the Bolt Creek Fire burn scar.

Strong winds may add to the headaches through at least Friday evening, with gusts as high as 40 mph in the cards for most of Western Washington, increasing the chance for power outages and downed trees.

In the mountains, more snow is likely at pass levels Saturday, followed by an abrupt shift to colder temperatures that may push snow levels close to the surface early next week. Overnight lows in Seattle are forecast near or below freezing starting Monday.

Washington and much of the West are heavily favored to see cooler-than-average temperatures next week, while the other half of the country runs warmer.

"Much cooler temperatures and showery weather will prevail by the start of next week," wrote Madelyn Kristell, a meteorologist at NWS Seattle. "Afternoon highs will struggle to get much higher than the mid 40s, with the overnight lows securely in the 20s and 30s. It is not too early to think about things and people that are vulnerable to the cold, including pets, pipes, sensitive plants, and demographics such as the elderly and young children."

While confidence in the long-range forecast is still low, Kristell said a wintry mix could be possible for areas east of Interstate 5 on Monday morning, along with western Kitsap County. Overall, forecasters expect things will begin to dry out by Tuesday.