A very wet weather pattern is setting up for western Washington through next week. More rain is on the way for tonight and tomorrow and an inch or more is possible in the lowlands. The mountains with higher elevation could see 2-4 inches of rain by Monday. The snow level over the mountains is not extremely low and it looks like the average level for snow will be hovering above 4,000 feet tonight and 5,000 feet for several days next week. Snow accumulation in the passes on Route 2 and Interstate 90 will be mainly rain with an inch or two of wet, slushy snow at Stevens Pass tonight. As we watch for more rain next week, it appears that the roads through the passes will be very close to the level between rain and snow for several days. Travel with caution and be sure to follow instructions on the posted WSDOT signs through the passes.
From Monday through Thursday, we expect an average of 2-5 inches of rain to fall in the lowlands of Western Washington, with the higher of these amounts mainly south of Puget Sound. Lower amounts of rain will fall across areas north of Everett and the in the northeast Olympic Peninsula. This much rain over a few days will cause some urban flooding where storm drains get clogged or overwhelmed. The risk of shallow landslides will rise next week as well. Shallow-rooted trees could fall when soils become completely saturated. If you live in an area where flooding has occurred in the past, you will likely see some of the same conditions this coming week.
A significant amount of rain is expected for our mountains, starting Monday and lasting through at least Wednesday. Rainfall totals over 6 inches inches will be common in the mountains. Snow levels near or above 5,000 feet means snow will fall only on the higher slopes and volcanoes. Much of the precipitation that hits our mountains will run off into rivers. That could push rivers like the Snoqualmie and Snohomish to flood levels just shy of Major Flood Stage. The most threatening days for flooding will be Tuesday, Wednesday and Thursday. You will notice sharp rises in the river levels by Monday as well.
The Snoqualmie River at Carnation is forecast to rise quickly Tuesday to near major flood stage by Tuesday evening, with another crest near or slightly above major flood stage on Thursday.
Other rivers are expected to reach moderate to minor flood stage. Best advice for residents along rivers or in areas that have flooded in the past: prepare for rising water and possible flooding next week!
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