Methods and limitations

How the data is built

Road status

Source-specific pollers fetch sanctioned traveler-information feeds on a 10-minute target cadence. The pipeline stores a successful-look record even when the payload is unchanged, stores changed snapshots separately, and derives status transitions from normalized records.

Snowfall and history

NOHRSC snowfall is sampled from a roughly 4 km gridded analysis at each pass coordinate. SNOTEL and GHCN stations are selected by proximity and screened for usable history. A nearby station can sit at a different elevation and microclimate, so the site always labels it as context rather than a roadway measurement.

Forecast

General weather comes from the NWS 12-hour point forecast serving the pass and includes the next two periods' conditions, temperature, wind and precipitation probability. Forecast snowfall is derived separately from the same location's raw NWS grid and summarized for the next 72 hours. Neither is a pavement or traction forecast.

Freshness

Pages distinguish the agency's update time from the time this pipeline observed it. A late or failed feed triggers a site-wide warning; stale data remains visible only with that warning and the authoritative link.