After a beautifully sunny weekend — the first dry one since Halloween — another atmospheric river will camp over the Puget Sound region on Tuesday and Wednesday.
Along with the torrential rain, the region is likely in for the same lowland flooding and slide danger as last week, according to the National Weather Service of Seattle.
A weak front moved into Western Washington on Monday, bringing light rain. The leading edge of the atmospheric river was expected to arrive Monday night, said meteorologist Dana Felton.
The river of rain is expected to stall over us for two full days, and snow levels in the mountains will move to 5,000 feet Monday and 6,500 to 8,000 feet by Wednesday, meaning we will see rain in the mountains instead of snow.
Heavy rain is forecast in both mountain ranges with 5 to 10 inches expected in the Olympics, 3 to 5 inches in the North Cascades and 2 to 4 inches in the Central and Southern Cascades, according to an NWS Seattle flood statement.
Flood watches are in effect through Thursday for King, Snohomish, Whatcom and Skagit counties, which will be affected by runoff from the Cascades. Possible flooding in rivers fed by the Cascades is expected to begin Wednesday.
Rivers in Mason, Grays Harbor, Jefferson and Clallam counties that flow out of the Olympics could begin flooding Tuesday.
A brutal combination of heavy snow and rain, what transportation officials called the worst mountain snowstorm in 20 years, closed Washington state’s four main highway passes for three days last week.
At Snoqualmie Pass, an additional 26 inches of snow fell by Saturday, bringing the season total to 286 inches, twice the usual accumulation.
Snow removal continued Monday on Snoqualmie and Blewett passes, as well as on Highway 97 between Cle Elum and Wenatchee, which reopened Sunday.
White Pass on U.S. 12 briefly reopened Monday afternoon, before a rockslide and unstable slopes west of the summit forced another closure.
WSDOT said crews will be out Tuesday morning to evaluate next steps to safely reopen the pass.
Stevens Pass, the most difficult corridor to clear, isn’t ready yet to reopen. Crews were still scooping away so-called “dirty slides” where snow is mixed with rock and wood, said spokesperson Lauren Loebsack.
“We’re working toward a Wednesday opening,” she said. Earlier in the clearing effort, WSDOT mentioned but didn’t guarantee a Tuesday reopening of Highway 2 and Stevens Pass.
With an atmospheric river heading that way, officials are worried about freezing rain on Tuesday, which would create a heavy top layer over softer snowbanks. WSDOT might need to perform more avalanche control work, said Loebsack.
WSDOT also reports that with Blewett Pass now cleared, some workers and machines were shifted to help clear the Tumwater Canyon area, a woodsy stretch just uphill from Leavenworth where a reported 208 snowslides occurred since last week.
Avalanche danger across the region was listed as moderate on Monday, down from “very dangerous” last week.
The possible impact of this week’s rain on the forecast is still being assessed, said Scott Schell, executive director of the Northwest Avalanche Center, but the center does not make predictions more than a few days out.
People planning to recreate in the mountains need to get in the habit of checking the forecast daily. When embarking on a multiday trip, the avalanche forecast should be checked every day, Schell said.
While lots of rain is on the way to the Seattle area this week, the region has a good chance of seeing another couple days of dry weather this weekend.
“It might be dry all the way through the weekend,” Felton said. “That would be the first time we’ve had three dry days in a row since September.”