I'll take a shot. With a substantial rainfall the creeks and rivers will rise and the temperatures will fall, although very briefly. This will cause the salmon that have been holding in the mouth to push up the rivers in a dash to spawn. But that is only part of it. The severe drought we have been experiencing will prevent the ground from being able to absorb this sudden downpour. This will result in very dirty water, slides, isolated flooding and what I believe to be very difficult fishing conditions. In my opinion, the fish will not be holding, and they will not be overly aggressive. Unless your lure is right on top of them I wouldn't expect them to bite. They have only one thing on their mind and that to get to the spawning grounds. I could very well be wrong (wouldn't be the first time), but if we get the expected downpours be careful out there, I expect some bad conditions.
We may actually dodge this bullet.
Friday and Friday night are actually supposed to fairly tame in terms of rainfall, but still enough to soak the ground without flooding the rivers. HOPEFULLY, when the BIG RAIN comes on Saturday, the grounds will be just wet enough to absorb enough rain that the rivers rise slowly and don't get too dirty. I know I'm probably being overly optimistic, but as of right now, the weather forecast is favoring this scenario.
However, some models are predicting as much as 3-4 inches by Monday which would cause dirty water no matter what time of year it was.
It could get interesting.