Area Forecast Discussion

KEY MESSAGES

- A few severe thunderstorms remain possible through 7PM this evening with isolated to scattered thunderstorm coverage. Strong damaging wind gusts around 60-70 mph is the greatest concern along with isolated large hail near 1 inch. An isolated tornado is also possible, especially over southwest Indiana. Torrential downpours may lead to poor drainage and runoff on roadways.

- The Extreme Heat Warning remains in effect through 7PM this evening. Heat index values are being observed between 110 to 116 degrees. Significant relief arrives for the second half of the week with temperatures cooling 10 degrees below normal.

- Rain chances return Friday and continue on and off into early next week. Some additional severe weather potential is possible between Sunday and next Tuesday. The heat and humidity also returns.

DISCUSSION

Issued at 1232 PM CDT Tue Jul 21 2026

The greatest heat impacts are now occurring across the FA this afternoon as a cold front begins to approach the FA from the northwest. A deep 500 mb trough is also digging into the Ohio Valley and will bring a significantly cooler airmass for the second half of the week with temperatures falling 10 degrees below normal. Highs will range from the upper 70s to lower 80s Wednesday through Friday. In the meantime, there is the potential for a few severe storms this afternoon and evening as the aformentioned front sweeps through.

The front quad of a 50 kt jet max at 500 mb is now approaching with SBCAPE values in the 5500 to 6500 J/kg range. The best effective bulk shear is setting up along our eastern counties with a gradient of 20-40 kts. Combined with a 30-35K theta-e difference and DCAPE values around 800-1000 J/kg, the potential for strong damaging wind gusts of 60-70 mph remains the main hazard of concern. Isolated large hail near 1 inch is also possible, but the extremely warm boundary layer may simply mean a lot of melting. While the low-level shear is not the greatest, there is a non-zero chance of a isolated tornado, especially over southwest Indiana. Torrential downpours will also be capable of causing runoff on roadways as there is ample moisture in the column with sfc mixing ratios around 20-22 g/kg and 2.2-2.3" peak PWATs.

Sfc high pressure currently over Saskatchewan will provide a break from the active weather pattern Wednesday through Thursday before rain chances begin to return on Friday as a shortwave ejects over the central Plains. The eastern extent of a ridge of high pressure begins to build in over the weekend, with high temperatures climbing back into the 90s by Sunday along with an increase in humidity. ML guidance is hinting at the potential for additional severe weather between Sunday and next Tuesday, as multiple disturbances ride along the ridge. Rain chances will be intermittent during this period.

AVIATION /00Z TAFS THROUGH 00Z THURSDAY/

Issued at 529 PM CDT Tue Jul 21 2026

A cold front is now sweeping across the region and will give way to mostly clear skies tonight. Brief MVFR cigs are possible across the northern terminals in the morning with initial cu before lifting to SCT-BKN VFR cigs in the afternoon. Winds turn light and northerly tonight, increasing to 6-11 kts on Wednesday. Isolated gusts around 17-18 kts are possible.

PAH WATCHES / WARNINGS / ADVISORIES

IL...Extreme Heat Warning until 7 PM CDT this evening for ILZ075- 080>094. Heat Advisory until 7 PM CDT this evening for ILZ076>078. MO...Extreme Heat Warning until 7 PM CDT this evening for MOZ076- 086-087-100-107>112-114. IN...Extreme Heat Warning until 7 PM CDT this evening for INZ085>088. Heat Advisory until 7 PM CDT /8 PM EDT/ this evening for INZ081-082. KY...Extreme Heat Warning until 7 PM CDT this evening for KYZ001>022.