Temperatures are on the seasonably cool side early on this Tuesday morning, in the upper 40s to lower 50s for most of us as we head toward 3:00am. However, they are running a few degrees above the forecast we’d had for the overnight. This is because of pesky low cloud cover still hanging tough early this morning. It is likely to persist a few more hours before shifting east and burning away with time through the morning. The satellite-based fog products in our VIPIR system are lit up like a Christmas tree this morning, but visibility reports at all weather reporting sites across southern middle Tennessee and north Alabama show excellent visibility. That, combined with the presentation of the cloud cover on satellite, dewpoints being a few degrees away from the temperatures, and the temperatures staying milder, lead me to believe that these are just low clouds instead of true ground-level fog.
Those clouds will shift on out of here as we head through the morning though, and that sunshine that we haven’t seen much of the last few days will allow us to warm into the mid to upper 60s by the afternoon. I wouldn’t be shocked if a few folks briefly sneak up to 70 or 71 this afternoon back near Savannah, TN and down into northeast Mississippi. Clear skies will allow us to have the efficient radiational cooling we had expected for early this morning, and that will allow temperatures to drop into the low to mid 40s by daybreak on our Wednesday morning.
The warming trend that begins today continues into Wednesday and Thursday as high pressure at the surface shifts to the east and we get more of a southerly flow. This will allow temperatures areawide to warm into the lower 70s for daytime highs and morning lows to moderate back to the upper 40s and eventually the low to mid 50s as moisture increases. This is all ahead of the next frontal system that comes in Thursday night into Friday morning. Ahead of it, clouds will begin increasing Wednesday night into Thursday, and we might even see a few showers as early as the morning hours of Thursday. However, the relatively better rain chances will hold off until Thursday afternoon and Thursday night, before wrapping up early on Friday morning, possibly even before daybreak. While we don’t expect severe storms or widespread heavy rain, there may indeed be a few isolated rumbles of thunder or heavy downpours with this system, as it will have more of a connection to Gulf moisture than the past few systems have had. Temperatures don’t change a lot behind this front, with the morning lows being the biggest difference because of drier air moving back in toward the weekend. This will allow morning lows to drop back into the mid 40s. Daytime highs look to stay into the upper 60s or lower 70s through the weekend before signs of a warm up going into next week.
While it is true that this system will have a better moisture connection from the Gulf than the past few systems and that there might be a few isolated heavy downpours or rumbles of thunder, we still don’t expect a lot of rain from this system. The GFS seems to be on the drier end of the model guidance with totals generally running from one tenth to near one quarter of an inch of rain, while the Euro is modeling a few more heavy downpours and embedded thunderstorms than the GFS, and this allows for slightly heavier rain totals, but still generally under an inch for everyone despite that. While we haven’t had a big rainmaker lately, the GFS has pretty consistently been a little too dry compared to reality with the past few systems while the Euro has been too aggressive days in advance before scaling back some. We think the truth is probably somewhere in the middle, and the NWS WPC office agrees, with their rainfall totals forecast being a general quarter to half inch for most folks. Keep in mind that that WON’T fall evenly for everyone, it NEVER does. Some folks may see an isolated heavier downpour that gives them a bit more (like the Euro model shows), while others don’t get as much and have totals that may be closer to the GFS. Until we get closer to the event and get it into higher-resolution modeling, our forecast has to be a general range of what to expect for the overall area.
Looking at general trends for next week into the 14 day time period, we do see signs of warmer temperatures as troughing in the upper levels shifts onshore across the western United States and we trend more toward ridging over the eastern areas. That does NOT mean flat out hot weather is coming, but we will probably return back to highs in the mid 70s or a little warmer as we head into next week and through the latter part of the month. That pattern change would also suggest we see more in the way of southwest flow in the upper levels. That often means southerly flow here at the surface, which would bring in moisture from the Gulf. It often also means weather systems ejecting out to interact with that moisture. We might just be starting to head toward a wetter and more unsettled pattern as we round out the month of October and head toward November. This should shock absolutely no one in our area as we often see the weather pattern turn more active as we head toward and into October as the jet stream begins diving southward.
This warmer and more unsettled pattern with systems ejecting out of the west does hint that we may have to start keeping an eye out for storm threats though. Keep in mind that our tornado season in the Tennessee Valley begins in November and runs through late May to early June. Some years when the pattern gets going a little early, things can start getting active in October in our part of the country. It’s too far out for us to be concerned about any storm systems at the moment, but we will just have to keep a general eye open as we head forward the next few weeks and beyond!