Weather or Not: How does fog form?

SHREVEPORT, LA (KSLA) - Fog, a common occurrence that could impact your morning commute. What exactly is fog and how does it form?

Fog is essentially very low-lying clouds. Fog is a collection of water droplets suspended in the air near the surface. There are multiple types of fog: advection fog, radiation fog, valley fog, and freezing fog.

The most common type of fog that we see here is radiation fog. The conditions in the atmosphere must be just right though for fog to form. Fog is most likely to form the morning after it has rained. This keeps the soil saturated and the water will evaporate throughout the night. This makes the dew-point depression, or the difference between the temperature and dew point, much smaller.

Throughout the day, the dew-point depression is higher. Once you cool overnight, the temperature and dew point become closer. When they are around the same value, fog forms.

Other factors that are needed for development are clear skies and light wind. Clear skies promote the evaporation of the moisture in the ground. Light winds cause the moisture to stay put near the surface and not mix with drier air aloft. Clear skies also help any warm temperatures from staying at the surface. This means the temperature will cool faster and reach the same value as the dew point quicker.

Fog can cause visibility issues on the road, preventing you from seeing cars or other landmarks right in front of you. It’s always a good idea to slow down, use your low beam lights, and leave plenty of distance between you and the car in front of you to stay safe.

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