Living in St. Louis, Missouri, along the Mississippi River, you might be accustomed to the occurrence of fog on your morning commute to school or work during the winter. What type of fog would you expect to find forming in St. Louis?

Valley fog

Explanation:

Valley fog, which settles into the hollows and basins between hills and mountains, is a type of radiation fog. When cooler, heavier air laden with condensed water droplets is trapped beneath a layer of lighter, warmer air and hemmed in by ridges and peaks, it can't escape and often lingers for days.

In the atmosphere, the fluid is wind. When the moist, warm air makes contact with the cooler surface air, water vapor condenses to create fog ... Valley fogforms in mountain valleys, usually during winter. Valley fog develops when mountains prevent the dense air from escaping.

Valley Fog

Explanation:

As the town is located adjacent to the river, this indicates that the water vapors from the river is being converted into the fog due to the lower temperatures in the winter. As the town of St Louis Missouri is surrounded by the mountain ranges, thus making it a valley. In these context the fog present here is termed as the valley fog.