Cold high-elevation tailwater — recovered from acid mine drainage in recent decades and now a strong wild brown trout fishery.
Hatch timing varies week to week with water temperature and weather. Cross-reference this calendar with Spring Creek Outfitter (Oakland, MD) or another local fly shop before planning a trip.
Auto-updated based on the current month. For trips today or this week, this is the section that matters.
Primary winter food
Spring emergence
Morning emergence
Bars span the typical emergence window for each hatch on North Branch Potomac River. The peak month is outlined and the current month is shaded gold. Mobile users see a month-card view below — a horizontal timeline at 375px is unreadable.
Primary winter food
Spring emergence
Morning emergence
Primary winter food
Morning emergence
Primary winter food
Morning emergence
Morning spinner falls
Primary winter food
Morning emergence
Morning spinner falls
Primary winter food
Morning spinner falls
Fall emergence
Primary winter food
Fall emergence
Primary winter food
Fall emergence
Primary winter food
Primary winter food
Primary winter food
Primary winter food
Spring emergence
Primary winter food
Spring emergence
Tap a species for the full profile — water temp triggers, fly patterns, and which other rivers run this hatch.
Chironomids · Snowflies
Year-round food source — the only consistent option on tailwaters in winter. On cold sunny days look for noses sipping clusters in slow water.
BWO · Olive · Little Olive
Most reliable Eastern hatch. Two emergences — spring (March-April) and fall (September-October). Best on overcast, drizzly days.
Red Quill · Dark Hendrickson
First substantial mayfly hatch on most Eastern rivers. Spinner falls in evening can be as productive as the dun emergence.
Pale Watery · Little Yellow May
The most important mayfly hatch on Eastern rivers. Reliable emergence + spinner fall every evening for 4-6 weeks. Match the spinners with rusty-bodied patterns.
PMD
More reliable on tailwaters where stable temps suit the hatch. Often runs concurrently with Sulphurs but emerges in morning rather than evening.
Spotted Sedge · Cinnamon Caddis
Workhorse summer caddis. Heavy emergences and egg-laying flights at dusk through summer. Drop a soft hackle on the swing during the evening.
Cahill
Pale yellow-cream mayfly. Less intense hatch than Sulphur but reliable across many Eastern rivers in late spring through early summer.
Hoppers · Ants · Beetles
Not a hatch but the most important summer trout food in many Eastern systems. Fish tight to grassy banks and overhanging trees. Hopper-dropper rigs are deadly July through September.
White-Winged Black · Curse
Tiny black-bodied mayfly. The spinner fall — not the dun emergence — is the main event. Look for clouds of spinners over flat water at sunrise.
Calendar entries are flagged "estimated" — regional patterns customized to this river. Always cross-reference with a local fly shop the week of your trip.
Bield: Fish ties USGS gauge data to hatch triggers and alerts you when North Branch Potomac Riverhits the temperature window for the hatch you're waiting on. Plan trips around peak emergence, not the calendar.
