Roaring Fork River above Difficult Creek near Aspen, Co.
Roaring Fork River · Rockies · USGS gage 09073300
Coldwater (summer mean 12.3°C — prime coldwater).
Water
59°F
Flow
33 cfs
Air
71°F
Sky
0%
Predicted hatches · 2026-06-16
PredictedGreen DrakeDrunella spp.1.00
Predicted by conditions; no reports yet. water 15.0°C (59°F) sits in the prime band (11-15°C); peak season; 8 days sustained ≥10°C; watch midday, often cloudy.
flies: Green Drake Parachute #10-12, Cripple, Hares Ear #10
PredictedSalmonflyPteronarcys californica0.60
Predicted by conditions; no reports yet. water 15.0°C (59°F) sits in the prime band (13-16°C); peak season; watch late morning through evening.
flies: Rogue Foam Salmonfly #4-6, Chubby Chernobyl, Pat's Rubber Legs
PredictedGolden StoneHesperoperla / Calineuria0.60
Predicted by conditions; no reports yet. water 15.0°C (59°F) sits in the prime band (14-18°C); peak season; watch afternoon and evening.
flies: Chubby Chernobyl #8-10, Yellow Stimulator, Pat's Rubber Legs
PredictedSulphurEphemerella dorothea / invaria0.60
Predicted by conditions; no reports yet. water 15.0°C (59°F) sits in the prime band (15-19°C); peak season; watch evening, the last two hours of light.
flies: Sulphur Comparadun #16-18, Sulphur Spinner, Pheasant Tail
PredictedEastern Green DrakeEphemera guttulata0.60
Predicted by conditions; no reports yet. water 15.0°C (59°F) sits in the prime band (14-18°C); peak season; watch evening; the spinner (Coffin Fly) falls at dusk.
flies: Green Drake #8-10, Coffin Fly Spinner, Drake Emerger
PredictedPale Morning DunEphemerella spp.0.30
water 15.0°C (59°F) sits in the prime band (13-18°C); shoulder of the season; watch late morning to early afternoon.
flies: PMD Comparadun #16-18, Sparkle Dun, Pheasant Tail #16
PredictedSpotted / Summer CaddisHydropsyche spp.0.30
water 15.0°C (59°F) sits in the prime band (14-19°C); shoulder of the season; watch evening, last hour of light.
flies: Elk Hair Caddis #14-16, Iris Caddis, X-Caddis
PredictedMarch Brown (Eastern)Maccaffertium vicarium0.30
water 15.0°C (59°F) sits in the prime band (14-18°C); shoulder of the season; watch sporadic through the day, midday into afternoon.
flies: March Brown #10-12, Hare's Ear, Spinner
PredictedSlate Drake / IsonychiaIsonychia spp.0.15
water 15.0°C (59°F) is warming toward the prime band (16-21°C); shoulder of the season; watch afternoon/evening; nymphs crawl to shore to emerge.
flies: Isonychia #10-12, Slate Drake, Leadwing Coachman
PREDICTED from the first-principles model only. Report-confirmed signal (fly-shop & forum reports) is the next milestone.