Gonna throw the Flag on this one , if you look close the chin of the snake seems to be on the ground/ice maybe even propped up to keep its mouth open .If he was an active snake that head would not be that low to the ground. Snakes will come out to sun beside their den in the winter if the air temp warms them but that has to be above 40° at best and sometimes other events make them move such as water flooding them oranimals digging them up. This one if for real might have denned in the wrong place and the lengthy cold spell made him look for a warmer den BUT, as long as its been this cold he would be seriously sluggish unless he was hibernating next to Browns ferry discharge water. Might be a new kind of radioactive snake!!!