Why has it been so foggy in Chicago? Here's what's causing it

As dense fog covered the Chicago area for a second straight day, many may have been wondering what’s causing such intense foggy conditions?

The entire Chicago area will remain under a dense fog advisory through 6 p.m. Thursday, potentially impacting both the morning and evening commutes.

“Most of the day will see fog with visibility down to one-half mile,” NBC 5 Meteorologist Alicia Roman said, adding that visibility could be near zero at times.

The dense fog is expected to last throughout the day, and across nearly all of northern Illinois and northwest Indiana, the National Weather Service said.

“Prepare for drops in visibility if traveling,” the NWS warned.

So what’s causing it?

Why is it so foggy?

According to NBC 5 Meteorologist Kevin Jeanes, the ingredients needed for fog include warm air, cold air, saturdated air and light wind.

“Basically it’s a cloud on the ground,” he said.

But there are different types of fog.

The fog currently in the Chicago area is what is known as advection fog.

“Warm air, moist air blows in from the south and if there is snow or cool moisture on the ground it will come in contact with the warm, moist winds,” the NWS reports. “This contact between the air and ground will cause the air blowing in to become cool. Then dew point rises and creates high humidity and forms fog.”

What else to know about the fog

According to NBC 5 Meteorologist Kevin Jeanes, the foggy conditions, along with the area’s current freeze/thaw cycle, were also causing more potholes to form on the roads.

“These are tough to avoid,” Jeanes said, adding that the low visibility and fog were making the conditions more challenging. “Right now, they’re kind of more widespread now that we’ve had a lot of snow melt.”

Martin said the Illinois Department of Transportation was working to fix a large pothole on the inbound Bishop Ford at 130th, with several cars experiencing damage.

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from NBC Chicago https://ift.tt/ZlgItk0