Around the Brazos Valley, we have seen several foggy mornings and days. It comes with the territory of being in a more humid environment. Although fog looks the same anywhere it forms, there are multiple reasons why we see it. In this blog, we discover what radiation fog is and how it forms.

Radiation fog is very common in most of the United States and doesn’t need a forcing mechanism like a front to make it happen. It forms at night when skies are clear and the winds are calm. At night, the ground naturally gives off heat that it absorbed during the day from the sun. When skies are clear, the Earth’s surface can cool off faster and the evaporation process is a tad more drastic. If there is a deep enough layer of moist air at the Earth’s surface, the rising warm air will condense and form fog once humidity levels reach 100%. Visibility can get down close to zero at times when radiation fog forms.

Valley fog is a very common type of radiation fog that occurs in the mountains. After sunset, the air gets colder on ridge and mountain tops. When air gets colder, it becomes very dense and sinks further down into the atmosphere. As this cooler air makes its way into the valley, it cools the warmer air below it. Often times, this air will be saturated enough to create fog. Once the sun comes up, valley fog tends to burn away quickly.

Have a weather question? Email Ploehn@kbtx.com and it can be featured in a blog!