Dense Fog in Animas River Basin, Colorado

Widespread fog, including areas of dense fog, developed within the Animas River Basin during the morning of January 9 following heavy snowfall. The KDRO ASOS at the Durango La-Plata County Airport reported two prolonged periods of visibility being reduced to or below 1 mile. During the first period, sporadic and brief periods of 1/4-mile visibility due to dense fog occurred. During the second period which began shortly before sunrise, dense fog reduced visibility to or less than 1/4 mile for about three and a half hours before slowly dissipating through mid-morning. No reports of injuries, damages, or fatalities were received.

A broad trough moved through the CONUS in mid-January with weak flow situated over Colorado. Embedded shortwaves moved through the trough, bringing bouts of active weather, including overnight from January 8 to 9. Strong snow bands developed ahead of the cold front moving through southwestern Colorado. As skies cleared and temperatures dropped behind the front, dense fog developed within some valleys near the San Juan mountains where heavy snow had occurred.