DALLAS — Another Dense Fog Advisory is in place for all of North Texas through 10 a.m. Wednesday morning.
This just means that fog may be thick enough where visibility is less than 1/4 mi. When that happens, driving can be impaired, as well as incoming and outgoing air traffic.
So, what's the scoop on this soupy situation? Well, here's the lowdown:
This is completely normal!
December and January (the middle of the winter) are the cloudiest and foggiest months of the year in North Texas. DFW Airport averages around two days a month during December and January, where the visibility is less than 1/4 mi. That may not sound like a lot, but it is much higher than the rest of the year. And there are likely quite a few more days where the visibility is not that low, but the fog is still thick.
So why are the winter months more favorable for fog?
- Cool and calm: Blame it on the recent chilly nights and light winds. Winter months are usually the coolest months of the year. While the winter can certainly be windy, fog can thrive when winds are light like they have been recently.
- Moisture, moisture, moisture: Recent rains have saturated the ground, leaving plenty of moisture around the area. When that moisture comes in contact with the cool air, clouds form. Fog is simply just clouds that are forming right near the ground.
- Long nights: Daylight is in shorter supply during the winter months. Daylight and sunshine heat the earth, helping to get rid of fog. So the longer the night, the more time fog has to develop, thicken up, and stick around. That lack of daylight and warmth also helps the ground retain more moisture than at other times of the year.
How do we get rid of it?
We need a change in the weather and the airmass in North Texas. Most of that is driven by wind. Fog has a very hard time forming when winds are strong or even just a steady breeze. So once the wind picks back up, fog's days will be numbered. Colder or warmer air (i.e., a cold front or warm front) moving into the area can help get rid of fog as well, but those are usually accompanied by wind.
When will this most recent round of fog end?
Probably not until Thursday, but maybe until Friday. Winds will be strong enough on Friday to help fog formation not be a problem. Fog will likely not be an issue Thursday afternoon, but it could redevelop Thursday night into Friday morning if the winds are weak enough.