Fly fishing report · West

Upper Lost River Drainage

An Upper Lost River Drainage report for Copper Basin, Howell Ranch, East Fork and North Fork context, with USGS flows, IDFG rules, remote access, hatches, flies, and safety.

Check flow & weather

Today's river scoreHigh source confidence

Caution

Best option: Wade.

Wading is in play only where your chosen access has clear footing, legal entry, and no forced crossings.

Updated Jul 13, 11:17 PM UTCUsually refreshes about every 45 minutes

Recommended approachWade

Mode scores adjust the river-wide score for the risks of wading, bank fishing, or floating.

Wade · Best fit66/100

Wading is in play only where your chosen access has clear footing, legal entry, and no forced crossings.

Bank / edge66/100

Bank and edge fishing remains a practical low-commitment option if access is legal and footing is safe.

FloatCheck

This report does not describe this as a primary mode. Verify legal access, depth, launches, and retreat options before planning around it.

Confirm before you leave

Flow and weather right now.

Use the flow trend to confirm the score before you leave. Weather can change the safest and most productive fishing window.

River strategy

Define the drainage before you fish it.

Upper Lost River Drainage is not one simple named reach. Treat it as a Big Lost upper-basin plan around Copper Basin, the East Fork, North Fork, and tributary water, then check the Howell Ranch gauge and IDFG rules.

Use the Howell Ranch USGS gauge for upper drainage flow context.
Do not use the below-Mackay tailwater gauge as the only upper-drainage decision point.
Check IDFG rules for Big Lost River, East Fork, North Fork, tributaries, and whitefish language.
Plan for rough roads, private land, and very limited services past Mackay.

Why this score moved

HeatUse caution

The NWS forecast is near 86F. Fish early and verify water temperature where trout stress is possible.

Public alertUse caution

A heat alert is active near this forecast point, so the score is capped until water temperature and fish-handling risk are checked. NWS alert: Heat Advisory issued July 13 at 2:50AM MDT until July 13 at 9:00PM MDT by NWS Pocatello ID.

Best mode nowUse caution

Wade: Wading is in play only where your chosen access has clear footing, legal entry, and no forced crossings.

FlowHelps score

USGS shows 319 cfs with a stable over about 6 hours trend. same-date USGS history (1904-2024, 116 readings) puts the normal middle range around 273 cfs-784 cfs. Flow is inside the same-date normal range, so weather, temperature, and access become the next checks.

SeasonHelps score

Summer: Prime high-country dry-dropper season when flows settle and temperatures stay trout-safe.

Read the water

What changes the plan.

The upper drainage is best when roads are open, runoff has settled, and water is cold but wadable. If the gauge is stale, roads are rough, or weather is building, choose a lower-risk river.

Cold stable high-country flow

Good for attractor dries, small nymphs, and short accurate casts.

Runoff

Avoid risky crossings and expect clarity and road access to be poor.

Low clear late summer

Use stealth, smaller flies, and stop if trout are stressed in shallow warm water.

Stale gauge data

Use extra caution and confirm conditions locally before driving deep into the drainage.

Field plan

Fish it with intention.

Best flows

Use USGS 13120500 at Howell Ranch as the main live flow anchor. It helps with the upper drainage trend, but it does not settle every tributary, meadow, or headwater condition, so pair it with recent weather, snowmelt stage, and clear public access.

When to skip

Skip or shorten the plan when roads are questionable, thunderstorms are likely, flows are too low or warm, dewatering makes fish handling risky, IDFG reach language is unclear, or legal access depends on crossing private land.

Local plan

Pick one realistic target before leaving: Howell Ranch and Big Lost context for the best flow signal, East Fork or North Fork only after checking IDFG reach pages, or Star Hope and high-country access only when road and weather conditions support the extra travel.

Backup water

If the Upper Lost is dewatered, stormy, access-limited, or too remote for the day, compare the Big Lost River below Mackay, Big Wood River, or Silver Creek after checking current rules and flows.

Hatches & flies

Bring a flexible box.

TimingWhat to watchUseful flies

SpringMidges, BWOs, early caddisZebra midge, BWO emerger, caddis pupa, pheasant tail

Reviewed pattern · report says “Zebra midge”Zebra MidgeLook for a very slim tapered thread body, evenly spaced contrasting wire rib, a small bead, and no tail or wing. The reviewed classic is black with silver wire and a silver bead. Red, olive, brown, glass-bead, jig-hook, resin-coated, or tailed forms must remain labeled variations rather than replacing the classic identity.See photos & how to fish it

Reviewed family · report says “BWO emerger”Blue-Winged Olive PatternsBWO describes a hatch group, not one fly. Nymph, emerger, dry, cripple, and spinner profiles must stay separate because they occupy different parts of the water column.See family guide + 2 more reviewed guides in the Fly Box

Early summerPMDs, caddis, small stonesPMD dry, elk hair caddis, stonefly nymph, hare's ear

Reviewed family · report says “PMD dry”Pale Morning Dun PatternsPMD names an insect group, not one fly. Pale nymphs, trailing-shuck emergers, upright or low-riding duns, cripples, and spent-wing spinners stay visibly separate.See family guide

Reviewed pattern · report says “elk hair caddis”Elk Hair CaddisLook for a tented elk- or deer-hair wing, clipped hair head, dubbed body, rib, and hackle palmered along the body. The body color should be labeled because tiers often match different natural caddis colors.See photos & how to fish it + 2 more reviewed guides in the Fly Box

Late summerHoppers, ants, beetles, caddisHopper, ant, beetle, caddis, perdigon

Reviewed family · report says “Hopper”Grasshopper PatternsHopper patterns share a substantial body and long rear-leg impression, but foam, deer hair, wing construction, and waterline differ widely among named patterns.See family guide

Reviewed family · report says “ant”Ant PatternsAnt patterns can be foam, fur-bodied, winged, or sunken. The narrow waist and paired body lobes matter more than one material recipe.See family guide + 3 more reviewed guides in the Fly Box

FallBWOs, midgesBWO dry, RS2, zebra midge, small streamer

Reviewed family · report says “BWO dry”Blue-Winged Olive PatternsBWO describes a hatch group, not one fly. Nymph, emerger, dry, cripple, and spinner profiles must stay separate because they occupy different parts of the water column.See family guide

Reviewed pattern · report says “RS2”RS2Start with the beadless architecture: two dark-dun Microfibett tails separated behind a slim, tightly twisted and visibly segmented dubbed abdomen; a fuller thorax; and saddle-hackle web clipped into a short angled wing bud. Rim Chung's original-style form uses natural beaver dubbing and hackle web. CDC- or Antron-wing ties, beads, curved hooks, flash, and tailless Avatar-style flies must remain labeled variations.See photos & how to fish it + 2 more reviewed guides in the Fly Box

Separate upper drainage planning from the Mackay tailwater.

Use maps to avoid crossing private land on the way to public water.

Fish small attractor dries and droppers through pocket water in summer.

Check roads and weather before committing to Copper Basin or side drainage travel.

Move on if low flows or warm water make trout handling poor.

Access & responsibility

Know the entry. Know the exit.

IDFG lists Big Lost River and tributary rules, including seasonal catch-and-release language and whitefish rules. Check the exact water before fishing.

Howell Ranch and Chilly area

Upper drainage flow-reference context with remote road planning.

Copper Basin

High-country approach with limited services and weather exposure.

East Fork Big Lost River

A separate IDFG-listed water with its own source checks.

North Fork Big Lost River

A remote tributary plan that should be checked against official rules and road conditions.

Transparent sources

Check the facts behind the plan.

Last material review: 2026-05-31

flowUSGS monitoring location: Big Lost River at Howell Ranch regulationIDFG Big Lost River Fishing Planner regulationIDFG East Fork Big Lost River Fishing Planner regulationIDFG North Fork Big Lost River Fishing Planner accessBLM Big Lost River Access Trail safetyNational Weather Service forecast point near Copper Basin

Common questions

Before you leave.

Is Upper Lost River Drainage one river?+

No. It is a drainage-style report for upper Big Lost, East Fork, North Fork, and Copper Basin planning.

Which gauge should I use?+

Use USGS 13120500 at Howell Ranch for upper drainage context, not the below-Mackay tailwater gauge.

Is access easy?+

No. Roads, private land, weather, and limited services all matter.

What flies should I start with?+

Use small attractor dries, caddis, PMDs, terrestrials, and tungsten droppers in stable summer flow.