Welcome Jimbo. As a rule, water clarity is down in winter from what it is during summer. Theories abound as to why; one is all that green salad you hooked into releases fine material into the water as it dies off and breaks down. With lower flows it is less diluted than in summer. Rain drain from feeder streams and from Berryessa can muddy it up at any time, but it clears out in a few days when the rain stops.