Our broken record weather pattern of fog, fog, and more fog may finally be changing soon… but not today. There’s a Dense Fog Advisory in effect until 11 a.m. for the San Joaquin Valley, and that may not be long enough as Monday’s fog should last into the early afternoon. Fog should not be an issue on Tuesday, however, as our first storm in over a month will move on in. It may not be that strong, but the potential Atmospheric River heading our way next week could be!
This has been Fresno’s foggiest season in over 20 years, and it’s not done yet. We’ve had 37 days of dense fog in Fresno so far (a dense fog day is when visibility drops to 1/4 mile or below), which is the most since 2002-03, when there were 40 days of dense fog. We are finally nearing the end of our fog season, however. As we get closer to Spring, the sun gets stronger as it rises higher in the sky, which burns the morning fog off quicker. Closing in on Spring also means that our days are getting longer and nights are getting shorter, which hurts fog formation. When our air cools down in the winter under clear skies, it eventually will cool down enough for the humidity to reach 100%, and fog begins to form then. Less time for the air to cool down because of the shorter nights means less fog forming in the Valley. We average 11 dense fog days under the long nights of January, 5 dense fog days in February, and only 1 dense fog day under the shorter nights of March.
Clouds will thicken up above the fog on Monday, which should prevent significant fog from developing Monday night. Tuesday will be cloudy, and showers should finally begin to fall for the first time in over a month by Tuesday night, lasting through Wednesday. This should be pretty light rain, and most areas in the Valley can look for less than 1/10″. Snow levels will be near 5500′, and there’s a Winter Weather Advisory up for the Sierra Nevada because of this storm…