JACKSONVILLE, Fla. – The National Weather Service has issued a Dense Fog Advisory for Jacksonville until 11 a.m. Wednesday for coastal counties and all of Duval County. Drivers should expect limited visibility on local roadways throughout the morning.
A reminder to motorists from the Florida Highway Patrol and Triple-A: Don't drive with your high beams on and it is illegal in the state of Florida to drive with your emergency flashers on.
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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.
Thursday afternoon a cold front approaches the area producing a band of showers. As this front pushes south, strong high pressure cranks up stiff NW winds dropping temps into the 40s Friday morning. It will be cold during the day with highs in the upper 50s.