Photo courtesy of Candice Yates in Powell Valley.
There's a saying I have learned since moving here. While I cannot exactly quote it, it goes along the lines of saying that for every fog in August, comes a snowfall in the winter.
Fog, for one thing, is a very common occurrence around here. We have lakes, which can contribute to moisture. Given a stable environment, moist air coming off of the lake can stick around and hang out in the low levels of the atmosphere.
We also have mountains and valleys. As I mentioned in "The Fog Blog," air can rush into the valley during the night and cool in the process to a point of saturation. It can then condense to form cloud droplets. In a stable atmosphere, that air will just stay in the valleys...valley fog. That is exactly what you see in the picture above.
Does that have anything to do with snow?
Here's where I start the number-crunching madness! While I cannot take records from every location for every year on record, I did go through some coded observations (called METAR) from the Tri-Cities Regional Airport. Some locations may have seen more foggy days, others may not have. Again, it depends on your location and the atmospheric conditions at play.
In the table below, dense fogs account for times when fog was in the area and visibility was less than a quarter of a mile. Snow days are defined by days where snowfall was greater than a tenth of an inch.
NOTE: There have been six total fogs, all of which were reported as dense, at the Tri-Cities Regional Airport in August of 2014.
What does this tell us? It tells us that the folklore is just that...folklore. If we were to take the sum of these numbers, it would mean that for every fog in August, you see 2.38 snowfalls. Meanwhile there are years like 2009 where there were four dense fogs followed by 23 snow days. Then, there are years like this past one where there were six dense fogs followed by nine snow days. Clearly, nothing is concrete. Welcome to weather!
But hey, I said it last week and I will say it again. All four of us here are meteorologists, and we, like all scientists, rely on the scientific method. The main principle of that method is to do everything in your power to disprove your initial hypothesis. Not so scientific, right? Do the research, and try to make your best inference.
So, is there any scientific reasoning in this?
I honestly cannot think of anything that would give us a defined relationship between fog during one month and snow in the following season. Fog is such a small scale and common occurrence around here, that using it to predict large scale wintry precipitation isn't appropriate.
Who am I to ruin the fun, right? I enjoy folklore as much as the next person. Just like I won't stop you from reading the Farmers' Almanac, I won't stop you from talking about weather folklore.
For those asking for science, here is something that will provide food for thought about this upcoming winter. NOTE: THIS IS NOT A FORECAST, JUST THOUGHT-PROCESSING.
Like last tropical season, this one to date has not been very active. The atmosphere needs to transport sufficient heat between the equator and the poles. It does so, in part, by large-scale weather systems. Being that there haven't been many tropical storms yet, will the atmosphere need to compensate for the lack of heat transport by triggering more of these weather systems in the mid-latitude during the winter months? We are currently in the thick of tropical season, so a lot can change. For now, it is only food for thought.
---Meteorologist Chris Michaels---
Facebook: Chris Michaels WCYB