The ridge of high pressure that has maintained a stranglehold on the Mid-South, bringing hot and humid conditions is weakening ever so slightly today, allowing a cold front to approach, but likely not pass through, the region. The additional dynamics (however weak) provided by the front will allow scattered thunderstorms to form this afternoon and linger into the evening and tomorrow as well. By Friday night, the front will retreat back to the north as high pressure re-builds for the weekend.
Some of the storms today and tomorrow could be strong, with the main threat being damaging wind gusts, frequent lightning, and flash flooding due to their slow motion. Many areas may not see rain, but some areas could easily see 1-2" in an hour. Even with increased cloud cover, temperatures will still rise into the mid 90s with heat index values in the 100-105 range before storms starting firing by mid-afternoon. Storms will likely linger into the evening, decreasing in strength and coverage after 9pm.
A repeat of today's weather is likely on Friday with more heating of the day thunderstorms that dissipate in the evening. Computer models indicate that while coverage will probably be higher over west TN and eastern AR today, higher coverage of thunderstorms may shift slightly south to southern west TN and north MS on Friday.
As the high re-establishes itself this weekend, thunderstorm coverage will decrease, heat will increase slightly, and Heat Advisories may again be needed. By early next week, the high again weakens and there are early indications that a cold front will push all the way through the area, bringing scattered storms early in the week and a return to more "normal" conditions for this time of year by mid-week, with lower humidity values. Average highs for late June run near 90 degrees and lows typically hit 70 (upper 60s in suburbs).
Check out the MWN Forecast for all the details for the upcoming week.