Another atmospheric river is aimed at the waterlogged Northwest, though the impacts are going to be a little different this week as colder air finally arrives by midweek.
We can expect rain and wind to increase tonight and by morning, it will be very wet and windy across the area leading to a terrible morning commute areawide. A Wind Advisory has been issued for most of the area starting tonight at 10 pm for southwesterly winds increasing to 20-30 mph through tonight and much of Monday. Wind gusts could exceed 45 mph in spots. Given the soggy and saturated soils, we could see more trees fall across the area, so isolated power outages are likely.
Rain will continue off and on Monday afternoon through Tuesday with heavy rain in the mountains at times. Colder air aloft arrives around Tuesday night, bringing the snow levels from above 6,000 feet to 3,000 feet or below. This means that Tuesday night and Wednesday, we’ll finally be in a snow globe in the mountains, so travelers used to rainy pass travel need to be aware that winter weather conditions hit late Tuesday and for the foreseeable future beyond Tuesday night, snow will be heavy at times and pass travel will be difficult.
While the changeover to snow late Tuesday in the mountains will herald the beginning of the end of this flooding episode, we expect 3-7″ of rain in the mountains before that changeover occurs. One to three inches will fall in the lowlands through midweek, and landslide risks will continue.
River flooding will be an issue for much of the week, though we likely won’t start seeing rises on area rivers until late Monday night into Tuesday as it takes some times for the heavy mountain rain to translate to the river systems.
While the river flooding won’t be as extreme as we saw last week, we’ll likely see waters getting back to major flood status on the Skagit River at Concrete and Mount Vernon on Tuesday and Tuesday night, respectively. We could also see some issues on the Skagit on Wednesday and Thursday too.
The Snoqualmie, Snohomish, Skokomish, and Nisqually Rivers are also expected to reach moderate flood stage in the Tuesday-Wednesday time frame with waters falling late week.’ Minor flooding is likely on other rivers.
Flooding from previous rainfall and dam releases will persist on the Green and White Rivers this week. Never drive around barricades as road structures could have been damaged from all this water.
By late week, rivers will be receding as heavy snow continues in the mountains. In the lowlands, chilly rain showers will persist into next weekend.