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Hatch predictions for 300+ US rivers — built from live water & weather, then confirmed against real fly-shop reports.

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Roaring Fork River Near Emma

Roaring Fork River · Rockies · USGS gage 09081000

Coldwater (summer mean 12.7°C — prime coldwater).

Water
58°F
Flow
210 cfs
Air
59°F
Sky
0%
Pressure
29.85 in
Wind
3 mph
Predicted hatches · 2026-09-15
PredictedSpotted / Summer CaddisHydropsyche spp.0.50
Predicted by conditions; no reports yet. water 14.5°C (58°F) sits in the prime band (14-19°C); shoulder of the season; 7 days sustained ≥12°C; watch evening, last hour of light.
flies: Elk Hair Caddis #14-16, Iris Caddis, X-Caddis
PredictedSlate Drake / IsonychiaIsonychia spp.0.25
water 14.5°C (58°F) is warming toward the prime band (16-21°C); peak season; 2 days sustained ≥14°C; 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.