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Watching the Gulf of Mexico system still. Quiet weather through Friday locally.


We're starting off with another sunny and mild day across the Tennessee Valley. Temperatures this morning are again in the 60s, but with a lack of cloud cover, we will warm rapidly through the 70s and again into the 80s as we head through the day. The muggy air is still off to the south, stuck south of that stationary front along the Gulf Coast. Easterly winds around high pressure centered over the Great Lakes and Ohio Valley will keep dry air in place another day before it shifts off to the east, and the front to the south washes out and southerly flow brings rich Gulf moisture back northward as we head into tomorrow and the weekend.


No big changes in temperatures expected for the next several days, with highs in the low 90s for Friday and remaining in the mid to upper 80s from the weekend into the first part of next week. There is another cold front just beyond the time range of this graphic though, that would knock temperatures during the day back into the upper 70s and lower 80s toward the middle of next week, and overnight lows back in the 50s.


Locally speaking, our weather stays dry and quiet through today and Friday, but the Gulf disturbance will gradually be working closer to the area, and as moisture increases going into the weekend, a few showers are possible as early as the daylight hours of Saturday. Most of the rain looks to hold off until either Saturday overnight or especially Sunday, but all of that is highly dependent on the exact track and timing of the system in the Gulf.


And that system in the Gulf is the big focus for our forecast still. The latest tropical satellite data this morning shows increasing thunderstorms over the Gulf, but they are located well east of the center of circulation that's located in the Bay of Campeche (southwestern Gulf of Mexico). This is a sign that dry air and strong wind shear are both significantly hindering the system at the moment. Those factors aren't necessarily go away either, which will keep this system from developing into an intense storm. However, the National Hurricane Center has increased the probability of this becoming a tropical depression or subtropical depression within the next 48 hours to 90%, and they stated in their morning outlook that they expect that to happen by tonight or Friday morning. Beyond that, it is very likely that this system becomes Tropical Storm or Subtropical Storm Claudette before making landfall on the Gulf Coast.


The latest run of the American GFS model has the system a little farther northeast and also faster, making landfall in Louisiana Friday night into Saturday morning and then moving into central Alabama by Saturday night. However, the GFS has a long-standing history of incorrectly latching surface lows onto thunderstorm complexes, and there are signs that it is doing that now. If that is what it is doing, it is incorrectly causing the tropical system to develop farther north and east than it would in reality, which changes both the track and the speed. The European model, which is in strong agreement with our in-house Baron Futurecast model that has a good track record for years with systems like this, is still on the track it's had the past few days. Developing the system gradually before making landfall in southwest Louisiana Saturday and moving up into north central Alabama by Sunday morning. This run of the European model is a bit faster, but only by a few hours.


The important differences are that if the GFS model is correct (and it seems suspect, as we explained), the bulk of the rain and impacts from the system would stay completely south of the area, basically from near Birmingham southward. If the European model is correct, the strongest winds and the tornado risk would probably stay south of our area, but the rain (heavy at times) would extend as far north as northwest Alabama and the first row of counties of southern Tennessee... and the flooding threat would extend as far north as the Tennessee River. The timing of the system would also be slower with the European model, with impacts from the system being from after midnight Saturday night through the early afternoon of Sunday.


A hurricane hunter aircraft is scheduled to be ready to fly into the system to gather data later today (unless the system remains too disorganized for that to be needed). Once we get that data back and fed into the various models, we will start to get a better idea of the ultimate track and timing of the storm system, which will be what dictates our local impacts (if any) here across the Tennessee Valley.


Tropical air gets left behind the system going into the first part of next week, and for our immediate viewing area, it may be that our heaviest rain happens early next week after the tropical system is gone, as the approaching cold front moves southeastward into that moist air mass. Rain and thunderstorm chances remain elevated Monday into Tuesday before that front moves through and brings another bout of drier and cooler air by Tuesday night and Wednesday of next week.

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