Scattered thunderstorms are developing across the northern Cumberland Plateau this afternoon, and what we’re seeing today is likely a precursor for things to come. Rain and storms are likely the next several days, with both an approaching cold front from the north and the remnants of Tropical Storm Fred from the south playing an impact on our weather.
Let’s start with Fred. He’s still a long ways away, currently centered over Cuba as a tropical depression. But he’s expected to restrengthen into a tropical storm once he reemerges over the open sea waters, and he’ll ride up Florida’s west coast over the weekend, likely making landfall somewhere around Apalachicola to Panama City Beach by early Monday.
The remnant tropical depression, once this storm moves inland, is currently expected to move through central Alabama and into Middle Tennessee by late Tuesday and early Wednesday. As it does, a deep southerly flow will develop over much of Tennessee, pulling in rich moisture from the Gulf of Mexico. If the tropical depression takes the path it’s currently expected to take, East Tennessee will be in an ideal position to see appreciable rainfall from the system.
Before that happens, though, an atmospheric trough will develop over the eastern U.S. and a cold front will sag southward before stalling somewhere over Kentucky, just to our north, over the weekend. That should enable a plentiful supply of Gulf moisture and provide an environment that allows for widely scattered to perhaps numerous thunderstorms both Saturday and Sunday.
For now, the National Weather Service has a 70% chance of thunderstorms in the forecast for the northern plateau region both Saturday and Sunday.
Exactly how this first period plays out is still in question. Some models keep thunderstorms in check over the plateau on Saturday, before increasing rain chances on Sunday. The short-term HRRR model, in particular, shows only isolated thunderstorms over the plateau tomorrow afternoon, with more numerous thunderstorms across eastern Kentucky and the Smokies.
The NAM is also a little skimpy with rain coverage tomorrow, and shows better rain chances on Sunday.
There’s going to be plenty of instability in the atmosphere this weekend, so it won’t take much to trigger thunderstorms either day. And how these storms develop over the weekend could impact what we see from the remnants of Fred early next week. Some isolated areas have already dealt with flooding early in the week. If we see heavy thunderstorms develop like that over the weekend and saturate the ground, the stage could be set for at least some minor flooding from Fred’s remnants Monday-Tuesday.
The bottom line: Rain and thunderstorms become likely each day after today, due first to an approaching cold front and then to the tropical remnants of Fred as he moves north out of the Gulf of Mexico. Thunderstorms are likely to be more widespread on Sunday than on Saturday, but all areas are susceptible to see storms on Saturday, as well. Heavy rain is the main threat from the tropical depression, and there could be some minor flooding concerns early next week. The heat wave we’ve experienced this week is about to snap, with temperatures going back to normal for this time of year.