Note that this is a VERY preliminary report. Right now long-range outlooks are still calling for a wet winter, with heavy weather predicted for the Northern Rockies in the second half of this month that could completely change the picture below. We’ll gain a better and better understanding of what our snowpack and summer streamflows will look like as winter and early spring progress. By April 1 we’ll have a pretty clear picture of how much snow we’ll have. By May 1 we’ll know if it’s melting early. So take the following with a HUGE grain of salt. At this point there’s no reason to begin changing trip plans you’ve made for late July and August.
The Importance of Snowpack
Visitors from many parts of the country are used to fishing tailwater and spring-fed trout streams that do not depend on winter snows for their flows. Most of our waters are fed by surface drainage and limited amounts of groundwater. Both factors are driven by winter snowpack: how much snow falls and when it starts melting in the spring. High snowpack that melts late means we’ll have a late spring melt that lasts into July, but strong, cold flows through the hottest parts of summer. A low snowpack that melts early means we’ll have a spring melt that ends in mid-late June, and we’ll be sweating our streamflows and water temperatures in late July and August.
High snowpack years mean a delayed start to some of our top fisheries (like the Lamar River for a chief example), but good fishing and healthy fish afterwards. Low snowpack makes for great early summer fishing, but high water temperatures, stressed trout, and the related stream closures come late July and August.
Winter Snows so Far
We saw a cold and wet October, including 18″ of snow on the ground in one storm here in Livingston. November and December have been warm and very dry. The closest ski hill, Bridger Bowl, didn’t open until about December 20 and still only has 18 inches of snowbase. My “rock board” is getting a workout for sure.
Current snowpack ranges from a low of 64% of normal in the Madison Basin outside YNP to a high of 105% of normal in the Yellowstone Basin inside and upstream of Yellowstone Park. The Madison Basin is more accurate, since the Yellowstone Basin includes areas near the Teton Mountains 150 miles from here that have gotten far more snow than the Lamar and Gardner Basins and the canyon stretches of the Yellowstone inside YNP where we actually do most of our fishing. The Northeast Entrance snow sensor on the upper reaches of Soda Butte Creek tells this tale: it’s currently at 71% of normal snowpack.
Summer Streamflow Predictions
Simply put, snowpack sucks right now and we need more snow, or we’re going to have low, warm water, stream closures, and lots of fires in late summer.
If things continue as they are, runoff will begin to tail off starting around June 10 and be over on all waters by July 1. The best fishing on most of the waters in the northern part of YNP and north to Livingston and beyond will take place from about June 20 through mid-July, with late summer fishing utterly dependent on cool weather that keeps water temperatures below the 70-degree mark. The Firehole and Gibbon on the west side of Yellowstone Park may begin getting too warm by June 10, as they did in 2015-2016, our last low-snowpack years.
2:00PM stream closures are likely throughout our operations area due to warm water starting by July 20 and lasting for a month or so. The Yellowstone is usually resistant to such closures, but I wouldn’t be surprise if closures have to be instituted all the way upstream to Gardiner, or even in Yellowstone Park.
Again, the above assumes that current low snowfall continues. Hopefully when I make the next update in a few weeks, I’ll have a completely different report.