Forecast Models & Scoring Methodology

A single 0–100 number indicating whether conditions are favorable for a given activity at a given location on a given day. It is a conditions fusion tool — not a safety rating, not a difficulty grade. Think of it as a weather readout for the trail: it describes the environment, not your plan.

The model combines signals conceptually, not by formula weights published here. The guiding principle: official closures override all other signals. If a trail is officially closed, the Go Score is 0 regardless of weather. Avalanche danger 4 or 5 acts as a hard floor. The weighting shifts by season and elevation — a 15-point weather penalty means different things in January vs. July.

• Official road or trail closure from managing agency
• Avalanche danger level 4 (High) or 5 (Extreme) in the trail’s zone
• Active wildfire perimeter within trail boundary or 1 mile of trailhead
• Elevation-factored AQI above 150 (wildfire smoke making outdoor exertion dangerous)
• Extreme heat above 107°F in AZ, NM, NV, UT desert trail areas

Go Score confidence is highest when: data freshness is under 30 minutes, source agencies are active and authoritative, and the trail sits within a well-covered geographic zone. Confidence drops when: a data source is stale (e.g., avalanche forecast older than 6 hours), rural road data is sparse, or the trail is near a coverage boundary between forecast zones. The computed_at timestamp on each trail card tells you how stale the score is.

• Go Score cannot account for personal fitness, experience, or acclimatization
• It does not predict snow stability or stream crossing danger (requires field assessment)
• It does not account for group size, bail-out options, or navigation ability
• Rural roads often lack monitoring data — road status may be unknown, not confirmed safe
• During rapidly changing events (storms, active fires), score may lag reality by up to 60 minutes

Go Score is designed to supplement — not replace — local knowledge, ranger station verification, and your own judgment. Use it as a screening tool: is this trail in reasonable shape today? Then do your own research for the final call. Never use Go Score as the sole input for backcountry decisions, avalanche terrain, or extreme conditions.

A set of per-hazard-type scores (0–100) that decompose the composite risk picture into distinct categories. Unlike Go Score (which is a single composite), Hazard Scores show you specifically where the risk is coming from so you can make targeted decisions.

Each hazard score combines severity (how bad could this be?) with probability (how likely is this today?). High severity + low probability may still score moderately. High severity + high probability scores in the red. The composite Hazard Synthesis score rolls up all five types using an escalating risk tier system (Tier 0–4).

Hazard confidence is degraded by: sparse gauge network (water), delayed community reports (terrain), rapidly building storm cells (lightning), and grizzly core zone data that updates sporadically. The lightning score is most volatile — it can change within minutes of a storm building. Trust the water score more than the terrain score when trail reports are old.

• Hazard scores are point-in-time estimates. Conditions can change faster than the score refreshes.
• Lightning scores do not capture intra-cloud electrical activity or bolt unpredictability.
• Water scores from USGS gauges reflect a specific measurement point — may not reflect actual crossing depth.
• Wildlife scores cannot detect unconfirmed sighting reports or recent scat/sign activity.

Use Hazard Scores for trip planning and route selection — e.g., choosing a lower-elevation alternative when wind and lightning scores are elevated. They are not real-time safety monitors. If a storm is approaching mid-hike, check the NWS directly — do not rely on the hazard score from your pre-trip briefing that morning.

An assessment of the risk and difficulty of the access route to a trailhead or destination, incorporating road conditions, surface type, elevation gain on the approach, weather on the drive, closure status, and cell coverage availability. Route Risk is pre-trip planning intelligence — it tells you what you might face getting to the trail, not what you face on the trail itself.

Road closure carries the highest weight — if the road is closed, Route Risk = Extreme regardless of surface or weather. If the road is open but the surface requires 4WD high-clearance and current conditions include recent rain or snow, the score escalates accordingly. Weather on the route matters more than weather at the trailhead — a clear day at the summit is irrelevant if the pass road is icy.

Route Risk confidence is lowest on rural Forest Service roads and county roads that have no monitoring infrastructure. Many USFS roads appear "unknown" rather than "confirmed safe" — the score correctly reflects this gap. Confidence increases on state highways monitored by CDOT/MDOT/WYDOT, and on routes with live camera feeds. Always call the nearest ranger station for USFS road status if the score shows "unknown."

• Rural roads are frequently unmonitored — "unknown" status means no data source, not confirmed safety.
• Road surface conditions can change within hours of rain or snow events that our data may not reflect until the next daily scan.
• Route Risk does not account for vehicle capabilities, driver experience, or group self-recovery capability.
• Wildlife on the road (bighorn sheep herd crossing, moose) is not tracked in real time.

Use Route Risk for vehicle selection, departure time planning, fuel and gear preparation, and communicating with riding partners about what to expect. Pair it with a ranger station call for USFS roads showing "unknown." Route Risk is not relevant to trail difficulty — a road can be Extreme while the trail itself is a pleasant walk.

A self-reported confidence level attached to every weather forecast on PeakScout, combining the NWS forecast’s own confidence tags, the degree of agreement between the Open-Meteo ensemble models, and PeakScout’s own assessment of forecast stability at that elevation and location. High confidence does not mean the forecast is correct. It means the forecast is well-supported by multiple models and the weather pattern is stable.

• Model disagreement — GFS and ECMWF diverge on precipitation timing or temperature
• Active frontal passage within 24 hours — small errors in timing create large forecast errors
• Afternoon monsoon building in AZ, NM, UT, CO — storm timing is notoriously difficult to predict
• High-elevation ridgeline forecasts in complex terrain — NWS models have known issues with mountain-top inversions and rotor clouds
• Extended outlooks beyond 3 days — directionally useful, not deterministically accurate

• Confidence is directional, not a guarantee. Even "High" confidence can be wrong 48+ hours out when a pattern shift occurs faster than models predicted.
• Microclimate effects in mountain terrain — a trail in a specific drainage can be 10°F warmer or colder than the nearest grid point.
• No humidity or dewpoint modeling at high elevation — whiteout conditions from fog or low clouds are not explicitly forecasted.

Weather Confidence helps you calibrate how much to trust the forecast when making trip decisions. A "Low" confidence day with good weather forecasted is not a green light — it means the forecast could easily shift. Call ahead. Check NWS directly at weather.gov for the specific forecast zone. Weather Confidence is a meta-layer — it tells you how hard to work to verify the forecast, not what the forecast says.