Dense Fog — San Juan River Basin, Colorado

2025-12-25 to 2025-12-26 · San Juan River Basin, Colorado

Event narrative

Areas of dense fog developed within the San Juan River Basin overnight from December 25 through 26. The KPSO AWOS at the Stevens-Pagosa Springs Airfield reported multiple prolonged periods of reduced visibility throughout the night due to mist and fog with numerous occurrences of 1/4-mile visibility from dense frog, each lasting 15 minutes to 1 hour. Fog dissipated shortly after sunrise. No reports of injuries, damages, or fatalities were received.

Wider weather episode

Southwest flow across the southwestern CONUS transported Pacific moisture into southwestern Colorado on December 25. Rain showers fell over much of the San Juans and nearby river basins as a result. Overnight into December 26, pockets of drier mid-level air developed over the same areas which had received rainfall. Clearer skies developed as dense cloud cover moved to the northwest and southeast of the San Juans. Favorable radiational cooling paired with the remaining surface moisture supported the development of dense fog in many of the valleys of southwestern Colorado.

Source: NOAA Storm Events Database, event_id 1302451. Narrative written by the NWS forecast office that issued the report.