Dense Fog — Northwestern San Juan Mountains, Colorado

2025-11-20 to 2025-11-21 · Northwestern San Juan Mountains, Colorado

Event narrative

Widespread, persistent dense fog developed within high-elevation valleys in the San Juan mountains following a round of terrain-driven snow showers. The KTEX AWOS at the Telluride Regional Airport reported multiple hours of 1/4-mile visibility from freezing fog throughout the majority of the night. No reports of injuries, damages, or fatalities were received.

Wider weather episode

A zone of deformation set up over the region ahead of a closed low, but a deep moist layer remained across the west slope of the Rockies. Overcast skies during the afternoon of November 20 kept the cool temperatures and near-saturated environment in place. This supported another round of snow showers early in the night of the 20th and the subsequent development of widespread dense fog.

Source: NOAA Storm Events Database, event_id 1300420. Narrative written by the NWS forecast office that issued the report.