It is now streamer fly season on most Park rivers and on Shoshone and Lewis lakes. Big browns are migrating on these, and in the case of the Madison River drainage they are accompanied by a fall rainbow run. So break out those six and seven weight rods and sink tip lines for rivers, or intermediate lines for the lakes. Have somber and bright patterns in the fly box, and a good camera to record the beautiful colors these fish put on to announce their migration. Also be prepared for stormy weather.