Only two miles north of Jackson, lying in the heart of the National Elk Refuge, flows Wyomings first fly fishing only stream, Flat Creek. It is a place so close to home that after a long day at work I can rush to gather my gear and be on the stream just moments later in pursuit of wary cutthroat.
This is not an easy stream to fish and for success you need both the right equipment and methods. I suggest a long rod, preferably 9 foot in length. For a line weight I go light, usually a four. Therefore, my favorite Flat Creek rod is a 9' #4. The light rod not only lands the fly softly on the water but also absorbs the shock when setting the hook with a light tippet.
One last important item of equipment on Flat is a good pair of sunglasses, preferably amber in color. These fish have subtle rises and are difficult to spot; the polarized glass cuts the glare and makes it easier.
Flat Creek usually offers excellent dry fly action. I very seldom get out on the stream and find no hatch. Therefore, I suggest a good selection of dries, preferably spring creek patterns such comparaduns and thoraxes. When Flat Creek opens on August 1st, you can count on a great Pale Morning Dun (PMD) hatch. It usually occurs early afternoon and tapers off early in the evening. The best pattern I've found is Lawson's Thorax Pale Morning Dun in a size 16 or 18. When presented well very few fish will refuse it. Other patterns such as a Light Cahill, Light Olive Comparadun and Harrop's PMD will also work well.
After the PMD hatch slows down between 5-7pm, then comes the caddis. These are usually small in size and of a dark variety. The best patterns for this are the Peacock Caddis and Black Elk Hair Caddis in size 18.
During the end of August and through September it's hopper time. When the wind whips through the grass and riffles the flat surface these fish look for hoppers. Fish them just like a crane fly with a short and heavy leader. When the wind doesn't blow expect to see some mahogany duns. Usually this hatch occurs in the mid afternoon and will bring fish feeding to the top of every pool. For this hatch any brown or tan bodied fly size 16 will work, but I prefer to use the comparaduns and thoraxes.
October brings my favorite fly fishing of the year. Now the weather is much less predictable. On warm sunny days a few hoppers still exist and hatches of October caddis and mahogany duns occur. However, I hope for cold overcast days, because that's when the Blue Winged Olives hatch by the thousands. Pools which earlier in the season held one or two fish will now have ten, all rising at the same time. The intensity of these fish feeding can be absolutely incredible. There is, however, one drawback; these flies occur in the difficult to see sizes 20 and 22. It can be tedious both tying them on your tippet and trying to see these flies on the water but it's worth it.
When you do get tired of straining your eyes, this is one of the few times of the year to fish a wet fly. Use some of the biggest and ugliest streamers or wets in your box. I've always found black and olive Wooly Buggers and Kiwi Muddlers to be devastating. If nymphing is your preference then try some big Yuk Bugs or Girdle Bugs as well as some size 18 Hare's Ears and PT's. Be sure to get them into those undercut banks, because that is where the big fish are.
Now for some final tips for Flat Creek. First, always approach its banks cautiously. Many banks are undercut and act as sounding boards. Blundering along the bank will scare fish for a long distance. Next, slowly walk along and try to spot the fish feeding. This is not the type of place to blindly cast, except when using craneflies and hoppers, because you will scare most of the big fish immediately. You must stalk your fish and plan your cast carefully. Be sure to wear dull colors, because bright ones will alert fish making them move under the banks before you even see them.