Current Conditions:
The East Gallatin is a legit option right now. Flows typically remain steady and clarity remains good enough for solid fishing. If rain or warm temps occur, it can become muddy enough for tougher fishing, but even with rain and some warm, the night time temps are still cold enough to keep the water clear enough to fish.
Fish are most active in the afternoons and nymphing will generally outproduce other methods. Trout are still concentrated in slower and deeper runs where they don't have to work hard to find food. Smaller mayfly nymphs and midge larva are best and try spring creek methods like yarn indicators to detect the subtle takes since fish aren't moving aggressively to the fly this time of year. Early season stoneflies also become more active as well and a rubber legs or small streamer dead drifted or slowly stripped can be effective.
Hatches of Blue Winged Olives will increase but the East Gallatin this time of year is going to produce sporadic hatches so the most consistent methods are nymph and streamer fishing.
The Month Ahead:
The East Gallatin will be a very solid local option. If daytime highs rise above 60 degrees and there is some rain in the forecast, keep your eye on streamflows as clarity can change quickly. When you do choose to fish the East Gallatin, focus your efforts during the hours after lunch when fish are most active or your best chance for a Blue Winged Olive hatch may occur.