The relative calm inland, even with strong southerly flows along the coast, lead to a pretty good night for migrants. When you look at the RTX loop you will see a pulse of birds moving down the Puget Trough. Probably water fowl moving from Nisqually to Ridgefield and Sauvie Island. But again the main movement was along the Cascades.
The ATX (Seattle) loop shows a heavy migration across the Straight and onto the Olympic Peninsula.
Looking at the wind map and the National Radar composite one will note the strong southerly winds along the Northeast Atlantic and the dearth of migrants. But the Central Flyway has a nice tailwind and migrants were aloft – dodging the weather systems along the route.