Heat Break? A cool front and a tropical system may hold the key to easing the heat soon!

A *Heat Advisory* continues from noon to 7 PM on Wednesday – for the highlighted counties in North Alabama. The heat index in Muscle Shoals got to 108°F on Tuesday.  A heat advisory literally means ‘that a period of hot temperatures is expected. The combination of hot temperatures and high humidity will combine to create a situation in which heat illnesses are possible. Drink plenty of fluids, stay in an air conditioned room, stay out of the sun, and check up on relatives and check up on relatives and neighbors.’

Hot, humid weather won’t be going away anytime soon; however, there is some hope of rain and thunderstorms reducing the heat by the end of the week!  Temperature soar to the middle and upper 90s again on Wednesday, and the heat index still could touch 105ºF or higher during the hottest part of the day.  A few isolated thunderstorms are possible Wednesday afternoon.  The odds of any one spot getting rain are around 20%, but as is often the case with summer storms, those few spots that do get rain could get a lot in a very short time!

Wednesday’s forecast highs

There are two main weather features to watch through the end of the week: (1) a cold front moving in Thursday and (2) a disturbance over the northern Gulf of Mexico that could become a depression or tropical storm (Barry) by Thursday or Friday.  Both of these features have sway over the weather around here in coming days; there are plenty of ‘moving pieces’ to the forecast, so expect some adjustments as we see things unfolding through the weekend.

  • The cold front: A very weak cool front (hardly a ‘cold’ front) stalls near North Alabama on Thursday and Friday.  The small change in air from one side to the other should be enough to enhance the chance of scattered thunderstorms through the end of the week.  Some of them could be heavy, too, thanks to an abundance of tropical moisture in the area.
  • The tropical ‘something:’ To put it in everyday language: this is the harder nut to crack.  We are watching something that amounts to a broad, weak swirl in the lower atmosphere over the Florida Panhandle that is slowly moving south into the Gulf.  There’s another ‘piece’ of this swirl in the upper atmosphere already out over the northern Gulf as of this writing, and since those two aren’t well connected, there is little room for immediate, explosive tropical development.  On the other hand, given a few days to organize over some very warm water (about 4ºF above average), it could ramp up quickly from a disorganized batch of thunderstorms to a strong tropical storm moving northwest toward Louisiana’s Gulf Coast.  The ultimate track of this feature over the weekend and early next week will have a huge net impact on the forecast in North Alabama and Southern Tennessee.

Two factors that will enhance showers and storms through the weekend

More about what could be ‘Barry’ soon: It’s not totally unheard of to see a storm develop this way; in fact, it’s rare to have a tropical system that didn’t start out as some kind of ‘feature’ from the mid-latitudes like a cold front, large cluster of thunderstorms (mesoscale convective system), or something of that family.

Current thinking is that it becomes a tropical storm and makes ‘landfall’ on Louisiana’s coast sometime Friday or Friday night.  While it won’t be a major storm like Michael, Harvey or any of those in recent memory, it will have a lot of wind and rain as well as a risk of a few severe storms for Louisiana, southern Mississippi and potentially southwest Alabama depending on just how far east it comes inland.

The farther east it tracks, the more likely it is to have an effect here in North Alabama and Tennessee.  What kind of effect?  It would mainly come from extra clouds and soupy tropical air enhancing daily thunderstorm activity around here on Saturday, Sunday, Monday and Tuesday.

If the storm is a little farther west, then our ‘going’ forecast for highs in the upper 80s and lower 90s with a ‘good’ chance of some scattered storms will hold.  We will adjust if need be as it becomes clear just how large this system is and how far east it comes inland.

Looking for the rest of the forecast? It’s always online at WHNT.com/Weather and in the “Daily Forecast” section on Live Alert 19!

-Jason
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