This week, it’s been a daily occurrence for a layer of fog to affect portions of the New England coast. The fog seems to follow the same schedule everyday, staying just offshore during the daylight hours then moving onshore at night.
Tons of sunshine over New England this Wednesday. Notice the fog bank just offshore. pic.twitter.com/zSVjebByh6
— Jackson Dill (@Jackson_Dill) May 9, 2018
This fog, or marine layer, is formed when warm air moves over cold water. It was Winter not too long ago, and now that Spring is here, the ocean water temperatures are still representing what they’re like in the wintertime. During the day, that warm, heated air over the cold water forms the marine layer. Meanwhile over land, the air mass is too stable for any of the fog to stay for an extended period of time due to the warm conditions. At night, however, as temperatures cool over land, the fog is able to move inland while persisting offshore.
The below image captured Wednesday evening shows how the cooling temperatures due to the setting sun allowed the noticeable layer of fog to move onshore and into the immediate coastline, including downtown Boston.