Foggy Vermont Morning Today. Get Used To It, Autumn Is Fog Season

Early morning visible satellite map shows fog
crawling through the river valleys of 
Vermont and surrounding areas. The Champlain
and Connecticut River valleys were also
quite fogged in.

 The National Weather Service office in South Burlington early this morning saw fit to issue a special weather statement warning commuters to be alert to dense fog.  

There was indeed a lot of dense fog around, especially in river valleys. This is obviously dangerous on the roads, as you could be zooming down the Interstate at 70 mph in clear air and suddenly drive into a wall of fog with near zero visibility. 

You might not see the accident or obstruction ahead of you until it's too late. 

Get used to these foggy mornings. Pretty much any relatively clear, calm night in the late summer and autumn will yield patchy dense fog during the early morning hours. 

The nights are starting to get cooler. As the chillier nights arrive, water vapor condenses into tiny droplets, which is the fog.

Rivers, lakes and the ground itself have warmed up after a long summer. The water and ground cool off much slower during the autumn than the air does. 

The warm water or soil heats up a very thin layer of air right above.  Then this slightly heated air rises and mixes with the cool air just above. The moisture in that formerly warmer air is then forced to condense into those tiny droplets and - viola! - you have dense fog.

Transpiration from leaves on the trees also contributes to the fog. The rising sun mixes and warms the air, so usually the fog dissipates by mid-morning. 

Since we expect at least a couple more clear, calm nights, expect more fog Friday and Saturday mornings, and maybe Sunday, too. 

Traffic cam shows dense fog along Route 7 in 
Brandon, Vermont this morning. 

By the way, these autumn dense fogs are great for leaf peepers when the foliage arrives. 

For photographers and others who admire nature, try to position yourself in an area you know is pretty, but on a particular morning is fogged in. 

Then wait for the sun to start eroding the fog.  The sunlight cutting through the mist is a sight to behold. The combination of that mist, the sun, the colored leaves, ponds and landscape are just gorgeous.

Fog becomes less likely late in the autumn.  It tends to be windier then, so fog can't form as easily.  By stick season, the leaves are gone, so they're not adding moisture to the air. 

In the meantime, take care driving in these foggy Vermont mornings. But also take the time to admire the beauty of it all.