For the last several mornings, dense fog has formed across the area. This fog developed due to the very cool temperatures that occurred during the morning hours, in conjunction with the relatively warmer bodies of water (ponds, rivers, lakes). This type of fog is called evaporation or mixing fog. This type of fog forms when sufficient water vapor is added to the air by evaporation and the moist air mixes with cooler, relatively drier air. The two common types are steam fog and frontal fog. Steam fog (which is what occurred recently in our area) forms when cold air moves over warm water. When the cool air mixes with the warm moist air over the water, the moist air cools until its humidity reaches 100% and fog forms. This type of fog takes on the appearance of wisps of smoke rising off the surface of the water.
Here is the satellite picture this morning (10/4/08). The white areas are areas of fog that developed near the rivers and lakes across our area:
This satellite picture is the same view, but without the state boundary lines, so the fog is more clearly visible:
The following pictures were taken this morning (10/4/08) by a NWS employee on his way to work from Metropolis, IL:
Looking east toward Dorothy Miller Park.
Looking south toward the Ohio River at a barge partially obscured in fog.
Normally, you would be able to see Harrah's Casino straight ahead, but this morning it was totally obscured by fog.
Travelling south into Kentucky via I-24 from Illinois, it wasn't long before you would encounter a large fog bank covering the Ohio River.
Here is the view just after crossing into Kentucky on I-24.
Remember, whenever you drive into dense fog ALWAYS slow down. This will allow you to increase the distance between your car and any cars in front of you that you may not be able to see due to the thickness of the fog. It is also important to switch your headlights to low beams. When you drive through fog with your headlights on high beams, a large amount of the light from your cars’ headlights will be scattered off the fog droplets and back into your eyes, which will reduce visibility even more and make it that much more difficult to see the objects in the road in front of your car and along the side of the road!!
As the weather pattern changes over the weekend into more of a southerly flow pattern, we should see less and less fog development. Low temperatures are forecast to be in the lower 50s tonight (Saturday night) and then rise into the upper 50s to lower 60s by early next week.