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Inland Dense Fog Advisory through 10am

West of Jacksonville seeing a foggy forecast

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JACKSONVILLE, Fla. –  A Dense Fog Advisory has been issued for our inland counties. The Dense Fog Advisory is in effect until 10am. The coastal fog could be persistent at the Beaches through noon. 

 Expect widespread visibilities reduces to a quarter mile or less. That level of fog makes for potentially dangerous conditions out on the road ways. Please travel at a lower rate of speed, be vigilant while driving, and use the low beam setting on your headlights.

Fog is heavily dependent on temperature, it forms when the temperature drops within a few degrees of the dewpoint. We need to warm a few degrees to allow the fog to dissipate, which should happen between 9-10:00 a.m. We are in a relatively quiet weather pattern right now which makes for fog prone mornings. When we warm nicely during the afternoon hours, the atmosphere absorbs quite a bit of moisture when the temperatures are in the mid to upper 70s. As we cool down overnight, the atmosphere cannot hold the same level of moisture when it cools into the 50s, and that moisture condenses out in the form of a cloud at the ground level, which we call fog.

How Fog Forms

Fog forms when the temperature drops within a couple of degrees of the dewpoint, all of the moisture in the air condenses out, in the form of a cloud, at the ground level.  Quiet weather patterns, with consistent broad swings in temperature make for fog prone mornings. The warm afternoon temperatures  allow for more absorption of moisture in the atmosphere, making you more likely to see fog when the temperatures cool down and the atmosphere can't hold as much moisture.

Fog dissipates when temperatures warm up. As the temperatures warm, the atmosphere can once again hold a higher capacity of moisture, so the droplets of water that make up the cloud are absorbed into the air.

Many times, fog will be more persistent and linger over large bodies of water, like the ocean or the river. The temperature changes diurnally more rapidly over land than the water, so as the land warm up more quickly, the fog dissipates first over the land.

The National Weather Service issues Dense Fog Advisories when they anticipate the potential for widespread visibilities reduced to less than a quarter of a mile. When visibility on the road is less than a quarter of a mile, that is the threshold for what is considered hazardous to drive in. 

Driving in fog can feel like driving while wearing a blindfold. Objects, such as other vehicles or traffic signals, may not be visible until the last moment- sometimes too late to take proper corrective action.

The two most important safety measures when you driving in fog are to slow down and turn on your low-beam headlights. By reducing speed, you increase available reaction time. And driving with your low-beam headlights on helps you to see the roadway more clearly and increases your visibility.

Additional tips for driving in fog

Use your windshield wipers to increase your visibility and reduce glare from oncoming vehicles.

If your vehicle is equipped with daytime running lights (DRLs), you may need to manually turn on your headlights, so your tail lights will also be illuminated.
Avoid sudden stops – and remember that larger vehicles need more distance to slow down or stop.

If you must stop, steer off the roadway as far as safely possible.

The use of hazard lights in inclement weather is illegal in Florida. However, it is permitted in Georgia.