Clouds of the Day - Foggy Night - Sunday, January 28, 2024

Moist relatively warm air flowing over deep snow cover often leads to the formation of dense fog. On this night visibility was reduced to less than 1/4 of a mile. The temperature of the air was in the 40s but the snow cover was near freezing and with dew points in the upper 30s fog developed. The dew point is the temperature when the relative humidity were reach 100%. As the air temperature is cooled to near the dew point by the deep snow cover fog begins to form. If temperatures fall below freezing ice from the fog in contact with sidewalks, streets, and highways can become ice cover if not treated with salt or other ice melt.