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

Forecast snowfall is derived from the NWS gridpoint serving the pass and summarized for the next 72 hours. It is not 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.