For the past week or two, many folks around the Great Lakes have been waking up to foggy mornings. Visibilities have frequently been below a mile, making it difficult to commute to work or school. But WHY has there been so much fog recently?
If you’ve been aware of the weather for the past week and a half, you know it has been unseasonably warm. Many towns in the Midwest have seen temperatures more than 20 degrees above average. In fact, South Bend, IN on Jan 21st, recorded a temperature of 61°F, 30 degrees above the normal high! Fog also happened to be a huge concern that night and the night before.
The recent warm weather has been the culprit for the fog. However, there are a handful of different types of fog. The one seen in the Great Lakes region recently can be classified as “advection fog”. Because it is January and many folks have already seen snow this winter, the ground is cold. This is not the time of year you should be digging a garden by hand. Freezing temperatures keep the ground hard during the winter months.
The recently unseasonably warm air came from the south from the Gulf of Mexico, bringing along with it a lot of moisture and spring-like temperatures. As the warm air passed over the cold ground (see picture below), the air cooled down to the dew point, which saturated the air and caused it to condense. Thus, a cloud, or fog, formed right above the ground.
How Advection Fog Forms
This type of fog usually occurs during the late winter and early spring in the Midwest because warm air rides over the cold, snow-melting ground. It just so happened that places saw the warm air as early as mid-January!
Forecasts show that colder, drier air is on the way, so there should be a bit less fog out there for the Great Lakes region.
For your latest Michiana forecast, go to ABC 57 Weather.