Hey Rev,
I've got a couple of things to chew on... First, I would rule out the lake turning over because it usually stays stratified until late November or even December. Lake Washington needs a really big windstorm before the thermocline goes away.
Everything fish-related seems to be a couple of weeks behind this year. Whether it is due to the late-warming spring or extra summer weather we are having right now, the fish seemed to have spawned later (or at least over a longer period of time than usual), and the usual algae blooms either happened way earlier or way later than usual depending on the lake. In rivers, salmon don't seem to be following their usual timing, either.
Anyways, I tend to believe that fishing for bigger fish gets really hard when there is a lot of food available. I think with the sunny skies and warm weather, the usual prey fish suspects haven't moved out to their fall/winter haunts yet. That could explain not seeing bait on the depthfinder. Also, a lot of the bait is really big right now because the fish that spawned in the spring have had a chance to grow all summer. Chew on this: if most of the available bait right now is larger, less of it may be available to the smaller fish, so they are biting more aggressively on the stuff you are offering them. The bigger fish though, still have tons of bait available to them.
There's another interesting thing about Lake Washington: longfin smelt. They typically spawn in February-March and begin to look very tasty to bass around this time of year. Before this time of year they are larval and really translucent. Now they are bigger, more colorful, and easier for bass to see. You'll also see perch start to nail them now, too. The extra interesting part is that for unknown reasons, smelt abundance is cyclical in Lake Washington. During even years, there is a stronger class of spawning fish. That means that in the autumn of even years there are a lot more smelt than during odd years, sometimes as much as 10 times more. Maybe, just maybe, those big bass have a lot of smelt to feast on. Smelt are typically schooled in open water, and if the big bass are keying on them, they may be suspended under those schools. But, you mentioned that you haven't been seeing bait. So... maybe not... but heck, it sounds interesting.
If the big bass aren't suspended right now, then my guess is that they are feeding heavily on the abundant bait right now in the typical haunts you know and are turning their noses at most artificial lures. If you see smallmouth spitting up smelt, let me know!!!
Actually, I take everything back. I think you should just look for largemouth. HA!
Chris