Low clouds traced the branching valleys of the Appalachian Plateau and the Cumberland River on a cool November morning, only to fade by afternoon. The transformation was captured in a pair of images from November 8, 2026, showing how valley fog forms and dissipates in the region.
NASA’s Terra satellite acquired the first image that morning using the Moderate Resolution Imaging Spectroradiometer (MODIS). In this natural-color view, low clouds appeared white as they filled many of the valleys. Autumn vegetation showed up in shades of brown and green. By the time the second image was taken, the clouds had vanished, leaving clear skies over the autumn landscape.
The afternoon view came from the Visible Infrared Imaging Radiometer Suite (VIIRS) on the NOAA-21 satellite. This false-color image made it easier to distinguish water, which appeared dark blue, from vegetation, which appeared bright green. The dissipation of the cloud layer exposed the rivers and lakes beneath.
Fog Formation in the Appalachians
The clouds visible in the morning image are fog, a type of cloud that forms near the ground. Foggy mornings are common in this region during this time of year. As nights lengthen, the ground has more time to radiate away the day’s heat. The air just above it cools to the dew point, the temperature at which air becomes saturated and water vapor begins condensing into the tiny droplets that make up fog.
Cold air is denser than warm air, so it flows downslope and pools in valleys. This causes fog to form there first. The morning image shows fog filling the branching valleys across part of the Appalachian Plateau in eastern Kentucky and southwestern West Virginia. Rivers and streams that run along many of the valley floors add to the effect by supplying extra moisture.
The same pattern is visible along the Cumberland River and its reservoirs in north-central Tennessee and south-central Kentucky. The presence of these water bodies helps sustain the fog until the sun warms the air enough to burn it off.
Weather Conditions and Travel Advisories
According to the National Weather Service, temperatures in many places on the morning of November 8 dipped into the 30s Fahrenheit before giving way to a mild, sunny afternoon. Forecasters reported locally dense valley fog that morning.
Dense fog had also blanketed a wider part of the region earlier in the week. This prompted advisories for hazardous travel conditions as visibility dropped significantly across the area. The November 8 images capture the typical daily cycle of this weather phenomenon, where fog forms overnight and clears by midday.
NASA Earth Observatory images were created by Lauren Dauphin, using MODIS data from NASA EOSDIS LANCE and GIBS/Worldview, and VIIRS data from NASA EOSDIS LANCE, GIBS/Worldview, and the Joint Polar Satellite System (JPSS). The story was written by Kathryn Hansen.
Source: NASA
