December begins Wednesday. What does that usually mean for weather in the Tennessee Valley?
After a year where rainfall has been significantly above average, November decided to change the tune. The Tennessee Valley only saw roughly 20-40% of the rainfall that it normally does for November. The climatology reporting station at the airport in Muscle Shoals, Alabama is actually running nearly 2.5 inches below normal for the month in the rainfall department. With this in mind, we are starting to see abnormally dry areas start to show up on the Drought Monitor, and it would not be shocking to see these areas expand a bit in the update that comes out this Thursday.
Now that we are ending November, we look ahead to December in the Tennessee Valley and what that may mean for the weather ahead. We can get an initial idea of what may be possible in the month ahead by looking at December climatology for the area.
December 1st is the start of meteorological winter, even though astronomical/calendar winter doesn't begin until December 21st. That makes it easier for meteorologists and climatologists to keep track of weather records. Our average high for the overall month of December is around 53 degrees, with us averaging in the mid 50s to start the month and only averaging 50 degrees for a daytime high as we get ready to ring in the new year. We can definitely still get warm this time of year though, especially if we find ourselves in the warm sector of a storm system or in a warmer La Nina driven weather pattern like what we may have ahead. The record monthly high for the area was 78 degrees set in 2016. Our overnight lows average in the mid 30s during the month, although we often see temperatures below freezing. It can get very cold this time of year. We had a historic cold spell in December of 1989 that set the monthly record low for the area at -5 degrees.
December also tends to be one of our wetter months across the Tennessee Valley. The month averages over 5.6" of precipitation for the month, and we have seen our fair share of heavy rain, thunderstorm, and even flooding events at this time of the year. There was major flooding in the area near Christmas of 2015 as just one example. December is also the first month that we actually average accumulating snow across the area. The "normal" snowfall total for our area in December is just shy of half an inch, but that comes from many years of not seeing any snow at all being averaged together with a few years where we see decent snowfall events.
When thinking of snow in December, the first thought on everyone's mind is whether we will see a White Christmas. That's where there is one inch or more of snow measured on the ground on December 25th. There is absolutely NO WAY to know whether or not we will see a White Christmas this year. However, we can get a basic idea by looking at the climatology for it to happen. As you would expect, the climatological probability of a White Christmas on any given year in our area is very small, less than 10 percent. However, it has happened before and can occasionally (but very rarely) happen in our immediate area. Much of the Tennessee Valley had accumulating snow on Christmas morning of 2010. The better probabilities of a White Christmas area typically in the Northeast and Great Lakes area where lake effect snow can happen, as well as in the Northern Plains and the Rocky Mountains.
Severe thunderstorms and tornadoes can also sometimes be a problem in our area in December. We are within the late fall and early winter portion of an extended tornado season in our area that runs from October to the end of May or early part of June. We only have to look back to 2019 when a tornado outbreak struck our area on December 16th, killing two people in Lawrence County, Alabama. Before that, long-tracked strong tornadoes struck Lutts, TN and Waterloo, AL on December 23, 2015. That goes to show that not only is severe weather (which includes the threat of tornadoes) possible this time of year, but some of the storms can be just as intense as they are in the heart of spring.