Thick fog continues to smother the San Joaquin Valley, lowering visibilities to near 0, which in turn creates school delays and makes the morning drive to work very challenging. There’s not much hope for the rest of the month either, as the fog will be sticking around for another week at least. We’ll keep our fingers crossed for more sunshine in February.
First the rains came in October, November, and December… filling the creeks, rivers, and lakes, and soaking the soils. Then, high pressure developed over California, sending the jet stream northward, and creating an ideal set-up for Tule Fog. And boy, have we had a lot of fog lately!
Strong high pressure over California pushes air down to the surface, and eventually creates an inversion, where the cold air gets trapped at the surface, while it becomes warmer in the foothills. That layer of cold air at the surface is VERY stable: no wind, no mixing, just the same thing over and over, until something (like a storm, gusty winds, or just the stronger Spring sun) breaks up the inversion. Our air quality can turn bad quickly in this situation, and if it’s been a wet winter, fog is almost guaranteed. Moisture from the now wet soil ‘juices’ up the shallow cold surface air, and with no mixing of drier air from the outside, we’ll stay cold, moist… and foggy…