top of page

Rain is gone. Cooler weather has arrived. Arctic air late next week!

You certainly don't need me to tell you that it's been rainy the past few weeks! After such a dry summer and large part of fall, we've definitely flipped the script on the weather here the past few weeks. Many locations across our area have gotten 1.5 to twice as much rainfall as they average on this calendar period for the last 30 days. Take our region's NWS climate reporting site at the airport in Muscle Shoals for example. They have recorded 5.66 inches of rain so far this month, more than double what they average by December 15th! That 5.66 inches of rain actually puts us a few tenths of an inch above normal for the whole month of December, even if we don't see another drop of rain through the end of the month!

As you can imagine, this is done significant work on the drought that's been in place since the summer. After getting as significant as "severe" drought designation a couple of weeks ago, recent rains across the Tennessee Valley have caused the official drought conditions to be REMOVED for our viewing area as of today's update to the Drought Monitor from the NWS. Keep in mind that this week's drought monitor update does not include the widespread heavy rain we saw late Tuesday overnight and through much of Wednesday. That gets factored in on next week's update, and it's very likely that will cause even the leftover "abnormally dry" conditions on the drought monitor to be removed for our area.

All the rain is gone though, with the big cold front bringing yesterday's downpours now moving off the East Coast. That means we are back to chilly air. Temperatures are in the mid to upper 40s as we head into the early evening, but it's not going to take them long after dark before they drop into the 30s. This drop in temperatures has us anywhere from 6 to 13 degrees colder now than we were this time yesterday!

Mostly clear skies, dry air, and slacking winds this evening allow for efficient radiational cooling... and that means we get chilly overnight. We will be in the mid to upper 30s by mid evening, and then headed for the upper 20s to near 30 or so for morning lows by daybreak on Friday. Clouds increase a little by afternoon on Friday, but we will still see plenty of sunshine, especially the first half of the day. Daytime highs will range from the mid to upper 40s for most, but I wouldn't be shocked at a brief stray 50 or 51 over northwest Alabama somewhere.

We see a mix of sun and clouds through the weekend as a dry and weak disturbance or two pass through. Daytime highs over the weekend will be in the lower 40s, but I could see some locations struggle to get out of the upper 30s on Sunday. Morning lows will be well down into the 20s. Another disturbance brings maybe a few rain showers Monday into Monday evening. The air mass will still be dry though, leaving questions about how much rain will actually reach the ground. We don't expect widespread or heavy rain. Interestingly, that dry air may allow for some evaporational cooling through the atmosphere above ground level as the rain showers first try to move in Monday. That MIGHT allow for a sleet pellet or two to get mixed in. However, even if that is the case, temperatures will be WELL above freezing. We don't expect any issues. Temperatures will generally hang in the mid 40s for highs and upper 20s to lower 30s for lows Tuesday into Wednesday.

Then BIG changes come as we head into the latter part of next week and closer to the coming Christmas holiday weekend. A major arctic cold front moves into the area late Wednesday night or Thursday. This brings an air mass originating straight from the Yukon area of Canada, and even partially from Siberia! Big time cold air floods the eastern and central United States for the latter part of the week and into the Christmas weekend. We're talking about the potential for daytime highs Friday through Sunday of next week to be below freezing. It's still a bit too far out for exact details on just how cold we will get, but reliable ensemble guidance is trying to lock onto the idea of daytime highs as cold as the lower 20s or maybe even the upper teens being possible next weekend, and overnight lows may be in the lower teens... if not colder! We'll be able to better sort out those details over the weekend as we start to get a little closer.

As is often the case this time of the year, you are going to hear about snow and rumors of snow 7+ days out on social media. That's just the way of the world in an internet driven society that relies heavily on social media for communication and has access to the raw computer model data that we use as tools to build the forecast. But, if you buy a new bookshelf for your home office, you don't stack all your books on the screwdriver that you use while you put the bookshelf together. It's just one of the tools that you use to create the final product. It's the same exact thing with a weather forecast. Those fancy snowfall total computer model maps you see floating around on the internet a week or two in advance are NOT a forecast. That is RAW data that has yet to be touched by a human meteorologist that has knowledge and experience with the atmosphere on how to sort through the noise in the raw data. It takes that raw data, along with knowledge and experience, to build the final forecast product.

With that said, there has been buzz about the potential for snow in the Southeast toward the latter half of next week. Above is ensemble snowfall output from the Euro ensembles, the GFS ensembles, and Canadian ensembles. On each image, the time period in question is circled in yellow. In each image, you can see that there is a solid signal among individual ensemble members of each model's ensemble group for the idea of less than an inch of snow accumulation late next week. You have to remember that this type of output does NOT account for melting, evaporation, mixing with sleet, or any other factors that may cause actual totals to be less. All the output above does is assume that every single flake that falls from the sky never melts or evaporates, and it gets to accumulate on the ground. We know in the real world, that is simply not true. Once we account for those real world factors, a model or ensemble's snow total forecast of a few tenths of an inch of accumulation actually translates to snow FLURRIES. There is a good signal for the idea of a few snow flurries or light snow showers mixing in with rain showers around next Thursday or Thursday night as the arctic air rushes in behind the cold front. That's very possible. Even though this is the classic situation of cold air chasing moisture that is running away, cold air of this caliber will squeeze out every bit of moisture it can in the atmosphere. Situations like this often produce some snow FLURRIES behind the cold front.

What's important to notice on these ensemble charts though, is that out of each ensemble group, VERY few members show any amount of snow more than that. Take the Euro ensembles above on the left, for instance. Out of 50 different ensemble members there, only four of them show the potential for any snow that would be more meaningful than flurries once we account for real world factors like melting, evaporation, mixing with sleet, etc. The GFS ensembles have about four members that do it, and the Canadian ensembles only have two! That's NOT the kind of signal we would want to look for in order to think that accumulating snow is on the table for the forecast. With that said, we are still a week or so away. There are many moving parts to the forecast with the arctic cold front that will move in, and aspects of the forecast certainly can change. However, as of right now, there is no credible or believable evidence of an accumulating / impactful type snow event in the Southeast late next week, no matter what you may see or hear from wild computer model runs shown on social media. We HAVE added the mix of rain showers and possibly snow FLURRIES to our forecast for next Thursday and Thursday night though. That will certainly help with the Christmas spirit, and just in time!

228 views0 comments
bottom of page