textproduct: Central Illinois

KEY MESSAGES

- Thunderstorms will bring a risk for damaging wind gusts on Thursday afternoon and evening, with the greatest chances for damaging winds south of I-72.

- Periods of heavy rainfall will be a concern from Thursday afternoon through Saturday. The greatest concern for heavy rainfall and flooding potential will also be south of I-72, where there is a 20-30% chance of rainfall exceeding 2 inches.

- Potential exists for extreme heat around the middle of next week, though some uncertainty remains.

DISCUSSION

Issued at 241 PM CDT Wed Jul 8 2026

** THUNDERSTORM POTENTIAL THURSDAY **

An unstable airmass with MLCAPE perhaps in excess of 2000 J/kg will reside south of an approaching frontal boundary on Thursday afternoon. It is anticipated that one or more MCVs emanating from overnight convective activity in the central Plains will serve as forcing mechanisms to help initiate convection on Thursday afternoon in central/southeast Illinois. Though shear even into Thursday morning may be on the weak side, the MCV(s) should at least locally enhance 0-6 km shear by Thursday afternoon/evening. In addition, forecast DCAPE values are in excess of 1100-1200 J/kg, particularly south of I-72 where the most likely track of an MCV is. All of these factors together indicate elevated damaging wind potential particularly south of I-72, with an SPC Level 2 severe risk there.

It is worth noting that there is some variability concerning the path/development of potential MCVs, with greater convective development perhaps occuring north or south of the most likely track.

** HEAVY RAINFALL THURSDAY - SATURDAY **

On Thursday, multiple model solutions depict precipitable water values in excess of 2 inches across much of central and southeast Illinois. Steering flow appears to be oriented perpendicular to the initial wave of rainfall Thursday afternoon, but a second wave perhaps associated with a second MCV later in the evening/overnight may provide more of a heavy rain threat with training elements becoming more likely. The path of the MCV(s) on Thursday, as well as associated convective development Thursday afternoon/evening, will be determining factors in how far south the effective frontal boundary pushes going into Friday. Should that boundary become stalled at some point, the heavy rain threat will increase further.

Chances of greater than 2 inches of rainfall at any given point near and south of I-72 through Saturday night currently are in the 20-30% range. Isolated totals in excess of 4-5 inches are not outside the realm of possibility, though confidence is low regarding where these isolated high totals may be most likely.

** MIDDLE OF NEXT WEEK **

Some uncertainty remains regarding the evolution of the pattern for next week. Most solutions depict a strong 500 mb ridge over the central and northern Plains, with variability regarding how far east the center of that ridge spreads and to what degree the ridge influences weather over central and southeast Illinois. A trough centered near Hudson Bay will also have the potential to provide some moderating influence to the ridge, as well as a chance for storms in northwest flow. WPC cluster algorithm for Thu Jul 16 currently shows about 20% of global solutions with the stronger Hudson Bay trough, with about 80% of solutions having a stronger central Plains ridge and/or a weaker trough to the northwest. CPC has the Midwest in a slight-moderate risk for extreme high temperatures during this time period.

AVIATION /06Z TAFS THROUGH 06Z FRIDAY/

Issued at 1234 AM CDT Thu Jul 9 2026

A modest SSW breeze less than 10 kt and VFR conditions will prevail overnight under the influence of a departing ridge. Scattered thunderstorms are expected to develop and move across central Illinois mid to late Thursday afternoon into the evening.

ILX WATCHES/WARNINGS/ADVISORIES

None.