Alpine Risk Score Methodology

How It Works

The Alpine Risk Score is not a conditions score — it's a safety hazard model. Where the Go Score answers "Is this trail in good shape?", the Alpine Risk Score answers "What will my body face when I get there?"

Six independent components are scored 0–100 and combined using wilderness medicine–informed weights. The composite is a single number you can act on before leaving the trailhead.

0–20
Low

21–45
Moderate

46–70
High

71–100
Extreme

Two conditions trigger a hard blocker that overrides the composite score: wind chill at or below -20°F (frostbite in 30 minutes), and a composite score ≥ 85 with multiple severe hazard components active simultaneously.

The Six Components

Alpine Risk = AMS×0.25 + WindChill×0.22 + Hypothermia×0.18
+ Traction×0.15 + Hypoxia×0.12 + UV×0.08

🏔️ AMS Risk 25%

Acute Mountain Sickness probability based on sleep elevation gap, summit altitude, and ascent rate.

AMS is the leading preventable alpine fatality mechanism. Weight: sleep elevation gap (most important) → summit altitude → gain per mile.

🌬️ Wind Chill 22%

NWS wind chill formula with 40% wind amplification above treeline (11,500 ft). Hard block at ≤-20°F.

Above-treeline exposure removes wind braking from trees. A 30 mph ridge wind at 10°F = -17°F wind chill. Frostbite window: 30 minutes.

🌧️ Hypothermia Risk 18%

Wet-cold compound risk. Precipitation in temperatures below 50°F creates hypothermia windows measured in minutes, not hours.

Freezing rain is the most dangerous weather event for alpine travelers. Wet insulation loses 90% of thermal value. Temperature lapse rate: 3.5°F per 1,000 ft.

🥾 Traction Risk 15%

Snow and ice coverage scored by depth, aspect, and freeze-thaw cycle status. Microspikes recommendation included.

North-facing slopes above 11,000 ft retain ice well into July. Freeze-thaw cycles (melt by day, freeze by night) create the most hazardous sheet ice conditions.

🫁 Hypoxia Risk 12%

Oxygen partial pressure model. Meaningful at 12,000 ft; significant above 14,000 ft where SpO₂ drops 10–15%.

pO₂ model: (1 - elevation_m/44330)^5.256. At 14,000 ft you breathe ~60% of the O₂ available at sea level. SpO₂ 80–85% is common for unacclimatized climbers.

☀️ UV Exposure 8%

+10% UV amplification per 1,000 ft elevation. Snow reflection compounds exposure. Burn time at 14,000 ft can be under 10 minutes.

Open-Meteo UV index is multiplied by the altitude factor. North-facing snow amplifies ground-reflected UV. Clouds reduce but do not eliminate UV — 50% penetrates heavy overcast.

AMS — The #1 Preventable Alpine Fatality

Acute Mountain Sickness is the most heavily weighted component because it is both common and preventable. Research from the Wilderness Medical Society shows:

~25% of visitors to 8,000 ft experience mild AMS symptoms
~50% of visitors to 14,000 ft without acclimatization experience AMS
The overnight elevation gap is more predictive than the ascent rate alone
Colorado's "Drive to 14ers" pattern (sea-level flight → same-day summit) produces the highest AMS rates

The model uses three inputs: your reported sleep elevation (default: 5,280 ft / Denver), the summit elevation, and the elevation gain rate (ft per mile). It applies a 3-tier penalty for the sleep gap, a graded altitude component, and an ascent rate modifier.

Sample Acclimatization Checklist (triggered for AMS Risk ≥ 50)

Sleep at least 1 night at 8,000–9,000 ft before attempting summit
Ascend no faster than 1,000 ft/day above 8,000 ft
Hydrate: 3–4 liters water per day; avoid alcohol/diuretics
Know AMS symptoms: headache, nausea, fatigue, dizziness
Carry ibuprofen or acetazolamide (consult doctor) for AMS

EMS & Medevac Proximity

Every Alpine Risk response includes an estimated distance to the nearest trauma center, based on state-specific alpine zone estimates. High-alpine wilderness zones in Montana, Wyoming, and Idaho routinely require helicopter medevac — ground EMS response times of 60–90 minutes are common.

These are conservative estimates, not live dispatch times. For route-specific SAR resources, check with the relevant ranger district before your trip.

File a trip plan. PeakScout's trip safety feature lets you designate emergency contacts who will be automatically notified if you don't check in by your expected return time. For alpine routes with high risk scores, this is not optional — it's essential.

Frequently Asked Questions

What is the Alpine Risk Score?

The Alpine Risk Score is a 0–100 index of physiological and environmental hazards specific to high-altitude routes (8,000 ft trailhead or 10,000+ ft summit). It fuses six independent risk components: Acute Mountain Sickness probability, UV radiation exposure, wind chill above treeline, hypothermia risk from wet-cold combinations, hypoxia from reduced oxygen at altitude, and snow/ice traction risk. A score near 0 means conditions are favorable; near 100 means extreme hazard. Unlike the Go Score (which measures trail conditions), the Alpine Risk Score measures what your body will face when you get there.

How is AMS risk calculated?

Acute Mountain Sickness risk is the most heavily weighted component (25% of the total score). The model accounts for three inputs: your sleep elevation the night before, the summit elevation, and the elevation gain rate. The overnight altitude jump is the single strongest predictor of AMS — climbing from Denver (5,280 ft) to a 14,000 ft summit in one day is roughly 3× higher risk than the same ascent from a camp at 9,000 ft. The gain rate (feet per mile) captures how quickly your body must adapt on the trail itself. This model follows Wilderness Medicine Society acclimatization guidelines and Lake Louise scoring parameters.

Why does UV risk increase with altitude?

UV radiation intensity increases approximately 10% for every 1,000 feet of elevation gain above sea level. At 14,000 ft, UV intensity is roughly 140% of sea-level values. Snow and ice compound this: fresh snow reflects 80–90% of UV, meaning you receive radiation from above and below simultaneously. The Alpine Risk Score adjusts the ground-level UV index (sourced from Open-Meteo) by the elevation amplification factor and flags burn-time windows so you know how quickly unprotected skin will burn.

What triggers a hard blocker?

Two conditions trigger a hard stop that overrides the composite score: (1) wind chill at or below -20°F, which creates frostbite risk in under 30 minutes on exposed skin; and (2) a composite score of 85 or above, which indicates multiple severe hazards compounding simultaneously. Hard blockers display a red "Do Not Attempt" warning in lieu of the numeric score. This is different from the Go Score's hard stops — Alpine Risk hard blockers are physiological thresholds, not official closure statuses.

What states does Alpine Risk Score cover?

Alpine Risk Score currently covers the five Rocky Mountain states with significant high-altitude terrain: Colorado, Montana, Wyoming, Utah, and Idaho. Coverage prioritizes trails above 10,000 ft at the summit or 8,000 ft at the trailhead. Arizona and New Mexico trails at Humphreys Peak and Wheeler Peak are not yet included in this release. Nevada's Ruby Mountains are also on the roadmap. State-specific EMS proximity estimates are built into the model for each covered state.

Does the score account for my fitness level or experience?

No. The Alpine Risk Score measures objective environmental and physiological hazards based on altitude, weather, and snowpack data. It does not know your VO2 max, altitude acclimatization history, pack weight, or experience with glacier travel. A score of 45 (Moderate Risk) at 13,500 ft is routine for an experienced alpinist but serious for a first-time high-altitude hiker. Use the score as a baseline conditions assessment — your personal readiness determines whether you should act on it.

How often does Alpine Risk Score update?

Alpine Risk Scores are cached for 3 hours after computation. Weather data is sourced from Open-Meteo at the trail's GPS coordinates and elevation. Snowpack data comes from SNOTEL station readings and community trail reports. On your first request for a trail, the score is computed live; subsequent requests within the 3-hour window return the cached result. The computed_at timestamp is always returned so you can see how fresh the data is.

What do the acclimatization recommendations mean?

When the AMS risk component is 50 or higher, or the summit exceeds 12,000 ft, the score includes an acclimatization prep checklist. These are evidence-based recommendations from the Wilderness Medical Society: sleeping at intermediate elevation before the summit day, ascending no faster than 1,000 ft per day above 8,000 ft, maintaining hydration (3–4 liters/day), and knowing the symptoms of AMS (headache, nausea, fatigue, dizziness). The checklist is informational — always consult a physician if you have any cardiovascular or respiratory concerns.

Data Sources

Alpine Risk Score draws from these real-time and reference sources:

Open-Meteo — Hourly temperature, wind speed, precipitation, UV index at trail elevation
SNOTEL (NRCS) — Snowpack depth and water content at alpine monitoring stations
PeakScout Community Reports — Trail conditions, snow/ice observations (72h TTL)
NWS Wind Chill Formula — Official wind chill computation for temps ≤ 50°F and wind ≥ 3 mph
Barometric pressure model — Standard atmosphere pO₂ as function of elevation (NOAA standard)
Trail database — Summit elevation, start elevation, length, aspect, and above-treeline flag from USFS/NPS

Disclaimer. The Alpine Risk Score is an informational tool for recreational trip planning. It does not replace formal mountaineering training, guide services, or evacuation planning. Conditions at altitude can change in minutes. Always check current forecasts from the National Weather Service and your local avalanche center. PeakScout is not liable for decisions made using this score. See full forecast disclaimer.