Snowpack, Spring Snowmelt, and Summer Water Conditions & Fishing Outlook – Early May Update

Snowpack, Spring Snowmelt, and Summer Water Conditions & Fishing Outlook – Early May Update

Snowpack, Spring Snowmelt, and Summer Water Conditions & Fishing Outlook – Early May Update


Winter and spring mountain snow and how this snow melts from mid-April through the end of May (and then runs off into the rivers in most of May and June) is the primary driver for the western water year. High snowpack and a late melt means higher than normal flows during the prime June-September season, which limits early summer fishing but improves conditions for mid-late summer and early September. Low snowpack and/or an early runoff means an early end to the melt and good flows early in the summer, but tough conditions in mid-late summer. All in all, we prefer slightly above normal snowpack combined with a slow and normal to late melt, which gets us started on our peak summer waters only a few days late, but keeps flows high and cold in the early August “danger time.”

Our Winter and Current Conditions

All in all, we enjoyed an above-average winter and early spring snow accumulation season, with snowpack currently running around 120% of normal throughout our operations area. It is now the cusp of the spring high elevation snowmelt (runoff). With current temperatures forecast to run from below normal to normal for the rest of May, we are now assured of a normal to late spring melt, a heavy spring runoff, and overall above normal flows for the core summer season. This is going to make June fishing tough. It’s going to help late July through early September.

The spring runoff has not started in earnest on any area waters, though some are muddy with low-elevation and medium-elevation snowmelt, since the late winter and early spring period has generally been cool and wet and there’s therefore patchy snow remaining even at low elevations (though most elevations under 7000 feet are now snow-free). With temperatures forecast to remain in the 50s and 60s for about another week, it’s very possible the spring melt won’t begin in earnest until May 15. This is about a week later than average and more like 3 weeks behind last year.

Yellowstone Park Opener Outlook

The Yellowstone Park season opens May 25 this year. The opener is always the Saturday of Memorial Day Weekend, which falls early this year. Because of the late start to the melt and the early opener, it’s very possible the early fisheries are “weird” this year. During average years, the fishable water is the Firehole and that’s it. During years with below-normal snowpack, the Madison, Gibbon, and perhaps Gardner are also fishable. This year we expect different waters to possibly be better, before they enter the heavy runoff and the Firehole takes over. Here’s our guess.

Please note: we won’t know if these predictions are going to hold or not until at least May 20, so check back then for an updated report.

The Firehole may be in full-scale runoff or not yet entering it on the opener. We expect BWO hatches and nymphing to be the most likely tactics to work. The critical blond Nectopsyche caddis are unlikely to start until early June this year.

The Madison and Gibbon may or may not be fishable on the opener, but will certainly be too muddy beginning a few days thereafter. If they are clear on the opener, I expect spring-style nymph and streamer techniques rather than hatches (Madison) and dry-dropper (Gibbon) to be the tickets.

The Gardner will likely be muddy, but if it has so much as a foot of visibility, it will fish well with big nymphs tight to shore. There may also be remnant Mother’s Day Caddis, but only if late May is VERY cold.

The Yellowstone in the Grand Canyon is going to be high, cold, and not clear, but it might be a sleeper bet for anglers interested in nymph and streamer fishing. We are going to look closely at this water right before the opener as it may be a great bet for early guide trips we have booked. It will get too muddy no later than June 1 and stay that way until late June. The Black Canyon is going to be muddy from the opener on. The lake to falls stretch is closed until July 15.

Slough Creek may be fishable in its lower meadow using streamers. If it is and you are experienced, fish there and expect the largest trout of the season. The rest of the Lamar Drainage will be muddy.

End of Runoff and Season Fishing Forecast for Various Waters

For most anglers, this is the “meat” of this post. Waters are listed in the approximate order in which they become fishable post-melt. Note that some waters are within my (Walter’s) operations area under my business Yellowstone Country Fly Fishing, but not really Parks’ Fly Shop’s, since they are a long way from Gardiner and YNP but not my home base in Livingston.

Missouri River

While it is running high and likely to get higher, peaking about May 20, the tailwater portions of the Missouri below Hauser Dam (“Land of the Giants” section) and Holter Dam (the longer, more-famous, drift boat section) are always fishable throughout the spring and are fishing well on nymphs, though dry fly action is limited with the high water. As always, these stretches of river will fish best before late July and again from late September into November.

Area Private Lakes

All are now fishable and have their most consistent fishing of the year from now through June, though Burns Lake holds on through July due to higher spring water content. These are going to be the best near-Gardiner options for larger fish through June. High summer sees these running a bit warm and weedy, and they come back on around Labor Day and remain good through late October.

Paradise Valley Spring Creeks

All are fishable year-round, though May and the first half June are not as good as March and April, late June and July, and October-November.

Firehole River

May be muddy on the opener and likely to see its peak runoff after June 1, a rarity. Nonetheless, this will be the most consistent river option in YNP through the first half of June and remain good through June, possibly through the first 10 days of July particularly in the mornings. After that will be too warm until about Labor Day and then get gradually better through the fall.

Madison River outside YNP

Fishing well now, but will rise and get steadily dirtier and be tougher for the last ten days of May and first half of June. Salmonflies in the latter half of June below Ennis Lake and the last few days of June and first few of July above Ennis.

Madison River in YNP

May be fishable on the park opener but then will go out of play by June 1 and be marginal for the first 10 days of June. Will then get progressively better and be good the last ten days of June and probably the first ten of July before getting too warm, with afternoons and possibly all-day fishing too warm in late July and early August, before coming back into play in the last ten days of August.

Gibbon River

Generally similar to the Madison, but less likely to be good out of the gate and more likely to hold up through July.

YNP Lakes

All except Lewis and Shoshone will be ice-free and accessible (albeit wet, sloppy, marshy messes) by June 1. Lewis and Shoshone will follow by June 10. All will fish best from mid-June through mid-July.

Gardner River

May be fishable on the opener, but probably too high and fast for most anglers even when clear enough through about June 25. After that will nymph well below Osprey Falls. Above Osprey Falls won’t be ready until at least July 4 and probably the 10th. Salmonflies begin below Boiling River in the last few days of June and above it about July 10. They will last in colder portions of Sheepeater Canyon through July and probably into August. The Gardner should have enough water that even below Boiling River it stays cold enough to fish well except on the hottest days all summer.

Jefferson River

Fishable right now but will go into runoff in the first few warm days. Will clear around June 25, but only remain cool enough to fish for at most two weeks. Will come back into play around Labor Day.

Yellowstone River, Grand Canyon

May be fishable on the opener but will get dirty no later than June 1. Will drop into nymph/streamer shape around July 1, with pockets of Salmonfly activity near hot springs then but stronger in the latter half of July. Will fish well from July through at least September except when overcrowded and/or muddy.

Gallatin River, Especially the YNP Stretch

Will drop into shape around July 1 and be good except downstream of Gallatin Gateway through fall.

Boulder and Stillwater Rivers

Will drop into shape in the first week of July and be best from July 10 through August 1 for the Boulder and another two weeks on the Stillwater.

Yellowstone River, Gardiner to Livingston

Fishable now and given the weather forecast should remain so at least off and on for another week before blowing out with runoff for real. Mother’s Day Caddis hatch is underway. The late runoff means this water will not drop into shape until at least July 1, with July 5-10 more likely. Salmonflies will occur at the same time. The middle of July onward will be very good this year on the Yellowstone, with enough water in the Paradise Valley section to keep good fishing going through August. As always the upper river will produce best for numbers, closer to Livingston for size. The fall fishing will be consistent given the high levels. We had good floats into the last week of October last season and this year should be no different.

Yellowstone River, Black Canyon

Generally similar to the Gardiner-Livingston section, but Salmonflies will start a few days later and last (particularly at the upstream end) through at least July 20 and probably July 25.

Small Streams in YNP

A few will fish by June 15-20, but most will drop into shape sometime in the first half of July and be best from mid-July through late August.

Slough Creek

Possibly fishable with streamers on the opener, but will blow out thereafter and otherwise not be ready until probably July 5-10, with the best fishing from July 20 to August 10 or so, though some fishing will continue until late September.

Lamar River and Most Tributaries

Muddy until probably July 4 and too high in the meadows for another week, though the canyon will fish after July 4. Will remain good (though crowded) until late September or early October.

Soda Butte Creek

Very small shot of a short fishable window right at the beginning of the season, otherwise not fishable until about July 10. Will be horrendously crowded from before it’s ready through early October at least, or two weeks after it’s consistent. We leave Soda Butte for West Yellowstone guides and tourists except when we have no other option given client time or mobility restraints. We just loathe the crowds here.

Yellowstone River: East of Livingston

It’ll be after July 15 before this water is low enough to be safe to float. This stretch killed some folks last season… Should have enough water to fish well into late fall after that, with late August this year being a good period to roll the dice in search of one or two monster browns on hoppers.

Yellowstone River, Above the Falls

Opens July 15 and as always is best shortly thereafter, though increasing numbers of cutthroats and good water levels this year should keep it worthwhile for a shot at a few big fish until late August. 2019 will be the best year since the late 90s here, something we can now say every year, since the lake trout are getting slaughtered at a quick clip and therefore cutthroat numbers are rebounding nicely.

One thought on “Snowpack, Spring Snowmelt, and Summer Water Conditions & Fishing Outlook – Early May Update

  1. Thank you guys for doing this. I love checking it when getting excited for my summer trip to the region. This year we are doing Ennis for the week of the Fourth… sounds like we may have timed it right!

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