We started to see a few signs of change today. After spending the last few days well into the 90s with a heat index in the low 100s, temperatures dropped back into the upper 80s to around 90 today. Temperatures will drop a little more over the weekend, and the high humidity will take a break also.
The upper level winds earlier this week were moving generally from west to east across the country as I talked about in my blog post on Tuesday. That 'zonal' flow pattern has evolved into one that has become a bit more amplified across the country. Think of 2 people holding a jump rope stretched out between them...then one person whips the rope and that causes up and down undulations along it's length...the same thing has happened to the upper level air flow across the US.
The upper level weather pattern will continue to amplify over the weekend. A strong 'ridge' of high pressure builds in the western US. This will bring them dry weather and extreme heat in some areas. Record highs well above 100 degrees could be set with places like Death Valley, CA approaching 130!
In the east however it's going to be the opposite. A 'trough' (pronounced 'trof') develops in the east. Very pleasant late June weather in the 70s and 80s will be common across the midwest and Great Lakes. We'll get in on some that cooler air and also some lower humidity.
However, the 'cooler' temperatures and lower humidity doesn't necessary mean we won't have rain to worry about. Troughs in the airflow are also the rain makers in the atmosphere. And since we'll be underneath the broad trough over the weekend and into next week we do expect to pick up some wet weather at times. The time of day most likely to bring showers and storms will be during the afternoon and early evening hours.
The chance of rain Saturday does appear to stay to our north. A few showers could affect areas in southern Tennessee during the afternoon.
As the trough digs a little farther south on Sunday, the shower and storm chances will move south also. It doesn't look like a rain out however. The chance for rain in any given spot is about 1 in 4.
This overall weather pattern looks to continue into next week, so we don't anticipate any huge changes. Temperatures will tend to run in the mid to upper 80s for highs (slightly below our average early July highs around 90), overnight lows will run in the 60s, and we'll see a daily chance for at least some scattered shower and storm activity.
WAFF 48 Storm Team