Data Sources

Known limitations: NWS / National Weather Service: Grid-point resolution is ~2.5km. Microclimate variation at high elevation not captured. · Open-Meteo: Not an official forecasting agency. Use as supplementary — NWS remains primary for official watches/warnings. · NOAA / National Centers for Environmental Information: Not real-time. Used for long-range seasonal briefings, not daily conditions. · RainViewer: Radar coverage gaps in mountainous terrain. Alaska and some rural areas have sparse radar penetration.

Known limitations: NAAE — North American Avalanche Exchange: Off-season (typically May–Nov): no ratings published; NAAE returns no data for many zones. Individual center APIs used as fallback. · CAIC — Colorado Avalanche Information Center: Seasonal — operates approximately Nov–April. Summer CO has no active forecasts. · GNFAC — Gallatin National Forest Avalanche Center: Seasonal. GNFAC zones also covered by WCMAC (West Yellowstone) and FAC (Flathead). · BTAC — Bridger-Teton Avalanche Center: Seasonal. WY has partial coverage — some ranges lack formal forecasts. · UAC — Utah Avalanche Center: Seasonal. UDOT also operates UDOT Avalanche for highway corridor forecasts. · WCMAC — West Central Montana Avalanche Center: Seasonal. Limited coverage area. · FAC — Flathead Avalanche Center: Seasonal. Glacier NP terrain has limited field observer coverage.

Known limitations: USGS — National Water Information System: Gauges in remote areas may have sporadic cell coverage, causing gaps. Some gauges are seasonal and go offline in winter. · SNOTEL — NRCS Snow Telemetry Network: SNOTEL sites are point measurements — conditions between sites vary. Not all trailhead elevations have nearby stations. · NRCS — Natural Resources Conservation Service: Forecast projections, not real-time observations. Accuracy degrades in extreme snow years.

Known limitations: USFS — US Forest Service: MVUM data lags trail status changes by weeks to months. Not all national forests publish real-time closure data. Some ranger districts lack digital closure infrastructure. · BLM — Bureau of Land Management: BLM field offices vary in digital data quality. Some routes are managed locally without central API updates. · NPS — National Park Service: NPS data coverage varies by park. Some smaller parks lack real-time condition feeds. Alerts are entered manually by park staff. · State DOTs — Dept of Transportation: No national standard — each state has its own data model, update frequency, and coverage depth. Rural state highways often lack real-time data.

Known limitations: NIFC / InciWeb — National Interagency Fire Center: Large fires only; small local fires may not appear. Perimeter updates lag field mapping by several hours. Historical fires removed from active feed. · NASA FIRMS — Fire Information for Resource Management System: Detects active thermal anomalies, not fire perimeters. Cloud cover blocks detection. Small/dim fires may be missed. Not a substitute for ground truth. · EPA AirNow — Air Quality Index: Monitors are sparse in mountainous terrain. Rural/wilderness AQI is interpolated, not measured. Wildfire smoke episodes may exceed monitor network coverage.

Known limitations: FAA — Federal Aviation Administration (TFR/NOTAM): TFR data is airspace-centric, not trail-centric. NOTAMs are text-based and require parsing. Some military TFRs have restricted access. · AWC — Aviation Weather Center (NOAA): ASOS stations are at airports, not at trailheads. Mountain weather often differs significantly from nearest airport. Alaska has sparse METAR coverage.

Known limitations: State Fish & Wildlife Agencies: Hunting data is seasonal. Wildlife alerts are opportunistic — dependent on field reports to agency. Not all states publish real-time wildlife data.

Known limitations: Recreation.gov: Reservation data is forward-looking; last-minute cancellations appear with a delay. Not all federal campgrounds are on Recreation.gov — some are managed by local agencies. · Colorado Parks & Wildlife (CPW): CO-specific. Some CPW data requires web scraping vs structured API.

Known limitations: ArcGIS Living Atlas / National Map: Esri maintains these layers; update frequency depends on source agency. Not all layers are authoritative for real-time conditions. · Third-Party Webcam Feeds: Not all areas have webcam coverage. Streams can go offline without notice. Webcam images are visual only, not machine-readable.