Thanks to colder than normal weather including some snow and killing frosts, hopper season is about to end on just about every park stream. So if you pursue big fish, streamers or big nymphs will get best results. This applies to Lower Gibbon, Madison, Lewis, Bechler, Fall, Snake, Lamar, and upper Gardner Rivers. Other than that, good top water fishing is reduced to the Firehole River where BWO and white millers make for good daytime fishing especially during unsettled weather.
For still waters, action on Beulah Lake is slowing because of cooling water. Wait a few weeks before trying Trout Lake. Some of the best lake fishing will be along Lewis Lake shoreline where wading to pitch streamer patterns (especially below the campground) can interest migrating browns and an occasional juvenile lake trout. Weather and physical condition permitting, carrying a flotation device with all accoutrements down the DeLacey Creek Trail to Shoshone Lake will get you into juvenile lake trout foraging around sunken weed beds. Use a full sink line, black or olive leech patterns, and dress for the weather.