Mike says Deer Creek is the most underrated whitewater kayaking run in Washington, and it's only an hour from Seattle.
Back in October he showed Nick Baughman, Anne Bilton, Kieran Thurlow and Allen Yip down it, here's Nick's video. The cover frame of Mike boofing a ledge is one of my favorite shots - classic Pacific Northwest whitewater and setting. Note the beautiful throwbag toss at just after 2:40, you can't see the bag but Mike is throwing from river left and it lands spot on.
Deer Creek is a good option if Robe Canyon is too high, depending on what the levels are doing. Mike likes to catch it when it's dropping, not when it's rising, and a little bit of flow goes a long way on this stretch. Apparently it has a somewhat flooded feel even at medium-low levels.
At low levels he calls it 6 miles of IV+ read-and-run whitewater with a few Class V rapids that are probably too low to run, at medium flows the character turns V-minus with marginally runnable V's, and at high flows it's continuous V with the harder rapids V+. Basically, a swim could mean losing a boat, especially at more substantial flows.
The Deer Creek page on Professor Paddle has outdated flow directions at this time (December 2016 - Mike wrote an update earlier this year but it never got posted).
He wrote the Deer Creek section for the Pacific Northwest Kayaking Guidebook and explains it all there, he also explains about two different access options which can potentially avoid a 3 mile hike in depending on if gates are open but it's a little complicated for this post.
Flow-wise, use the North Fork Stillaguamish gauge to determine if the river is dropping, and if it is use the gauge at the takeout bridge on Deer Creek to check the run. Mike correlated this really carefully and it's more helpful than the Professor Paddle beta.
The bridge gauge is designed to correspond to how quickly levels fluctuate on Deer Creek and how long it takes to get to the put-in from the bridge, so 'low' on the gauge at a dropping flow is a good low, and 'low' on the gauge at a stable flow is actually medium on the river. Have fun out there!