Following a wet week in southern California, folks were greeted to a clearer sky on Thursday…somewhat. Check it out:
One of the last impacts of the recent frontal passage is an interesting "fogscape", common for post frontal mornings when plenty of low level moisture and light winds remain for fog development (as opposed to drying offshore surface flow seen behind some frontal passages). #CAwx pic.twitter.com/ncivqCqRVS
— NWS San Diego (@NWSSanDiego) December 5, 2019
Captured this interesting multi-level view this morning in East county pic.twitter.com/8joMxBqkQI
— Paul Gagnon (@PGBrews) December 5, 2019
While the air was clear a little higher up, it was foggy down at ground level in the San Diego area. Surely, people in California are no stranger to the “May Gray” or “June Gloom” that visits often. The marine layer frequently moves onshore and provides thick, foggy conditions. However this instance was a little bit different. Let’s explain:
It all started with the decent amount of rain that fell on Wednesday. Many areas picked up 1-2″ of rainfall from Tuesday into Wednesday. The sky then cleared Wednesday night into Thursday morning. However, the ground level was still saturated. The wet ground then saturated the air around it. When saturation occurs, the temperature cools. This set up a temperature inversion.
A temperature inversion means the air at the surface is cooler than the air above (or aloft). This is known as a stable environment. It means the air stays put. This allowed for the foggy landscape to greet folks heading out the door early Thursday morning!