From my experience, Valley fishes best with cloudy skies, after a rain, or when the water is flowing well. Bright skies and low/slow water are usually signs of a potentially frustrating day. Go there on a cloudy day and nymph a grey scud - San Juan Worm combo and you'll catch fish. Throw nymphs and dry's in tight spots close to the bank where all the tree roots and log's are, those are generally the most productive areas for me.