A look back at recent rainfall and a look forward to December climatology in the TN Valley
After a long, dry summer and fall for the most part, we've finally gotten some decent rain around here the past few weeks. Here are the updated rainfall stats for the climate reporting station for our area at the Northwest Alabama Regional Airport in Muscle Shoals. The airport itself managed to get 4.19" of rain in November, putting the month there 0.04" above average. There is still a deficit for the year though, with the 45.74" measured so far putting us just over 3 inches in the negative. That deficit is shrinking with time, however.
Most all of the region has seen a widespread 3 to 5 inches of rainfall over the past month, with a large portion of that falling in just the past seven days (especially Tuesday and Tuesday night). This has definitely helped in terms of soil moisture, but we are still running at 50% to 80% of our normal rainfall for the past 30 days, with the exception of a few areas that got to near normal. The good news is that the forecast ahead calls for more potentially heavy rain over the next seven days, mainly later this weekend into next week, and that will help more. The latest update to the Drought Monitor has actually upgraded a good bit of our area to D2 level "severe drought" conditions. However, that update did not take into account the rain that fell Tuesday into Tuesday night. The update issued next Thursday will factor in those rainfall totals, and it is likely that we will see some decent improvement across the area. With a wet pattern taking shape over the next couple of weeks, it is very possible that we drastically improve (if not eliminate) a large amount of the drought across the area, and the official drought forecast for December from the NWS Climate Prediction Center office calls for the drought to be removed this month with time across our area.
December has arrived though, and that means it's time to look forward to a new month and see what climatology says about how the weather typically behaves across the Tennessee Valley. While the winter solstice is on December 21st, "meteorological winter" begins today. This makes it easier to keep up with weather and climatology records. The average high for our area in the month of December is 53 degrees, but it begins in the mid 50s today before working down to around 50 by the start of the year. Our average monthly low is around 34 degrees, but we usually average 36 by the start of the month and end up just below freezing at 31 degrees for an average to end December.
We know averages aren't always what happens though. We can certainly be warm in December, especially when we're in the warm sector of an approaching storm system. The record high for our area for December is 78 degrees, set back in 2016. We can also be downright cold too! The record monthly low for December was -5 degrees, set back in the brutal cold December of 1989!
December is typically the wettest month we average on the board here in the Tennessee Valley. Our average monthly precipitation comes in at 5.68 inches, and since we are sliding into colder weather, almost a half inch of that on average, ends up as snowfall. It doesn't snow every December, but it very well certainly can, and sometimes there can be big winter storms on occasion. The record monthly snow for our climate reporting station in Muscle Shoals in the month of December is 11.1 inches, set in 1963!
One concern we also have in the month of December is severe thunderstorms and tornadoes. We are in the middle of our tornado season here in the Tennessee Valley that runs from November through the end of May, although an argument can be made that it starts in October and ends in the first half of June some years. To the right of the graphs above are maps of all tornado tracks across the region in the month of December, dating back to the 1800s (and the map on the right specifically shows EF2 and greater tornadoes only). As you can see, we are definitely no stranger to December tornadoes in and near our area, and sometimes, they can be just as intense as the tornadoes we see in the middle of the spring. This is why it is important to be vigilant of severe weather year round... have a safety plan in place, and have multiple reliable ways of hearing watches and warnings, including something that will wake you out of your sleep in the middle of the night. Many of our fall and winter tornadoes happen in the dead of night, and they can sometimes be intense too!