Walter just posted an in-depth snowpack and runoff report and an outlook for summer streamflows and fishing over at Yellowstone Country Fly Fishing. Rather than reinvent the wheel, we suggest you click this link for the details.
Long story short, we have low snowpack and runoff is near its peak. We anticipate a low runoff, an early end to runoff, and low, warm streamflows this summer. In general the best opportunities will be in the first three weeks of July before things drop too much, though after that the fishing will still be good as long as it’s not super hot and dry. If it IS super hot and dry… well, we might be doing a lot of 6AM to 2PM trips and morning half-days.
Walter made a snowpack and streamflow update on his business website. Rather than reinventing the wheel, go check it out.
In sum, we had an early start to the spring melt due to downright not weather the last few days of April, but early May is forecast to be cool and wet. This should stall the HEAVY runoff until at least May 15-20 and will certainly lead to good fishing on the Yellowstone, Boulder, and Stillwater once the first flush of runoff drops out in a couple days.
Overall, snowpack is low. We expect low streamflows and an early start to most summer fishing as the water drop sooner than usual. This is good for late June and early July fishing. It’s not so good for late July and August fishing, when we anticipate low flows and warm water that might prompt “early-on, early-off” trips for optimum results as well as some mandatory closures in warm, low-elevation waters. These waters are mostly in Montana, though it’ll be a short season on the Firehole this June.
An early warm snap over the past few days has resulted in the Yellowstone blowing out with the first surge of the heavy spring snowmelt. This means that for right now our fishable options have shifted to the Boulder, Stillwater, Lower Madison, and Missouri Rivers and to area lakes.
Here’s a flow graph. The river has almost quadrupled in volume over the past few days:
Below is the river’s level. It has come up about 2.5 feet since midnight on April 28. YIKES. This is the highest level the river has been since early July, 2020. Even if it had somehow remained clear, such a big jump would have made the fish weird for a few days. Since it’s full of chocolate brown mud and sticks, the trout are all hunkering on the bottom.
The good news is that this is not the onset of the full-scale runoff that will see the river completely out of play until well into June. The weather is forecast to drop back into the 50s-60s this week, and the NOAA forecast for the second week of May is calling for below-normal temperatures. Therefore we expect the river to drop back into shape by late this week and stay there through at least May 15 (assuming the outloos are accurate). There might not be much dry fly fishing, but these bumps in flow followed by drops before the heavy runoff hits typically bring great streamer fishing.
Snowpack Update and Summer Streamflow and Fishing Forecast