I know on lakes when the water warms channels head for warm water. I would think flatheads will. Shallow coves where crappie spawn is supposed to be a good bet. I dont know how shallow flatheads will go. Channels will move up into 2 & 3 feet of water. Will flatheads move back to the deep water once the temp. starts to drop at night. Mabe a cove that its shallow at the back and gets deeper when it gets closer to the main lake will be a good bet. I dont have much fathead experience fishing lakes.