FARMERSBURG, Ind. (WTWO/WAWV) – Advection fog. First thing you need for this type of fog is cold ground. Then you need warm, moist air moving over the cold ground. At this point you start to see fog developing.
This happens as the air is cooled to saturation by cold from the ground cooling the air above.
This typically occurs with a warm front passing through in the winter.
Unlike radiation fog, advection fog may form under cloudy skies and with moderate to strong winds. Initial stability is relatively unimportant since low level cooling makes the air stable near the ground, allowing the fog to form. Once formed, it may move across the landscape, pushed by low level winds. Advection fog can last for several days and is most common in the U.S. on the West Coast.
Radiation fog is a very common type of fog throughout the United States and the Wabash Valley. It’s most prevalent during the fall and winter.
It forms overnight as the ground cools and stabilizes. Clear skies and calm winds are key ingredients in forming radiation fog.
When this cooling causes the air to reach saturation, fog will form. Fog will first form at or near the surface, thickening as the air continues to cool. The layer of fog will also deepen overnight as the air above the initial fog layer also cools. As this air cools, the fog will extend upward.
The most favored areas for fog development are sheltered valleys where there is little to no wind and locations near bodies of water. Wind would disrupt the formation of radiation fog. Radiation fog is usually patchy, tends to stay in one place and goes away the next day under the sun’s rays. Thicker instances of radiation fog tend to form in valleys or over calm bodies of water.
There are many other types of fog.