Midweek still dry, Thunderstorms back in time for the weekend
We are sandwiched in between two weather disturbances this Wednesday morning. One is a pesky upper-level shortwave trough over the Carolinas and the other is the big upper-level low over the Four Corners that is bringing all the big snow to the Rocky Mountains. Some of those folks went from temperatures in the 95-101 range on Sunday and Monday to accumulating snow and travel problems on Tuesday! It is also that upper low that was originally supposed to help usher in a cold front to the area late this week, but like we have been talking about the last couple of days, it looks like that front stalls to our north before it ever reaches us.
In the meantime, dry air is still in place across the area in the mid and upper levels of the atmosphere, despite dewpoints at the surface gradually creepy up into the upper 60s. This means that the atmosphere is still too dry for rain, or much in the way of cloud cover for that matter. So, again for your Wednesday, we expect mostly sunny skies and a light easterly wind with afternoon highs in the general 85 to 90-degree range. Afternoon highs have been a couple of degrees cooler than models have shown for southern Tennessee when compared to observations, and the Shoals have run a couple degrees warmer. Winds will go calm overnight, and with not much cloud cover around, temperatures will be able to drop down to around the dewpoint. This may mean some patchy fog across the area after midnight tonight and early Thursday morning.
Thursday and Friday won't be too different from today overall, but deeper moisture will gradually be increasing from the east as the shortwave high pressure over the area breaks down, and the pull from the upper low out west brings some of the moisture from our east into the area. Clouds will be on the increase more, although we still expect partly cloudy skies. With the deeper moisture moving back in though, there might be a few isolated thunderstorms across the area each afternoon, although most locations will probably stay dry when looking at the viewing area as a whole.
Deeper moisture will be firmly entrenched across the area as we head into the weekend, just in time for that front to approach from the northwest but stall just upstream as the upper low ejects into the Great Lakes and gets absorbed into the upper-level jet stream again. That increasing lift will mean scattered to fairly numerous thunderstorms across Saturday and Sunday. And with the added cloud cover and rain, afternoon temperatures will be a few degrees cooler as well, only getting into the mid-80s, and a few folks might stay in the lower 80s if they see a good bit of rain. It won't be an all-day washout for anybody either day, but if you have outdoor plans, make sure you have a way of keeping an eye on the radar.
Both the Euro and GFS ensembles seem to be set on the idea of a slight cool down as we head into next week. I don't think it's a full-on cold front moving in, but it looks like the strength of the upper-level ridge relaxes some as a weakness gets left behind from the departing upper low. This very well might allow high temperatures next week to ease down into the upper 70s and lower 80s. However, rain and storm chances will still be around, at least in a scattered fashion. We will be fine-tuning those forecast details as we get closer.
The tropics are still alive and active in the Atlantic basin as we are the day before the official peak of the Atlantic hurricane season that happens on September 10th. We still have Paulette and Rene on the board, even though Rene has weakened to a tropical depression overnight. Rene will very likely recurve northward well out in the open Atlantic. There is still a good chance that Paulette will do the same, although we will have to watch the strength of the subtropical ridge over the western Atlantic. There is a window for Paulette to recurve in this pattern, but if she misses it, she would be steered westward by that Atlantic subtropical ridge. Then, we have another intense tropical wave about to roll off Africa that already has a "high chance" of development as outlined by the National Hurricane Center. This one will likely be named Sally, and we will have to watch it very carefully. It may be on a more southern track through the Atlantic and eventually into the Caribbean as we head down the road.