textproduct: Central Illinois

KEY MESSAGES

- Scattered thunderstorms will track along and northeast of a Lincoln to Paris line through 6pm this evening. A few of the cells will be capable of producing gusty winds and large hail.

- There is a Slight Risk (level 2 of 5) for severe weather on Wednesday. It appears another storm complex will develop across Iowa late tonight, then track southeastward across central Illinois from late morning through the afternoon. Damaging wind gusts and isolated tornadoes will be the primary hazards.

DISCUSSION

Issued at 245 PM CDT Tue Aug 11 2026

**** Scattered Storms This Afternoon ****

The severe thunderstorm complex that rolled across northern Illinois this morning has pushed an outflow boundary southward to the I-74 corridor this afternoon. As expected, scattered thunderstorms are developing along this boundary. The atmosphere across central Illinois is presently moderately unstable (MLCAPEs 2000-3000J/kg), but weakly capped thanks to very warm air aloft. The RAP shows the cap gradually weakening as the afternoon progresses and MLCAPEs increasing to around 4000J/kg along/east of the I-57 corridor after 21z/4pm. As a result, think the narrow line of storms currently ongoing along a Hoopeston to Bellflower line will intensify as it drops southeastward...posing a risk of marginally severe wind and hail. Will continue to monitor cells between Peoria and Bloomington as well, but think the main location for a few wind/hail reports through 6pm will be along/northeast of a Lincoln to Paris line.

**** Storm Complex on Wednesday ****

After a mostly quiet night, a short-wave trough ejecting out of the Rockies will trigger another cluster of thunderstorms across Iowa late tonight into Wednesday morning. With the effective boundary pushed a bit further south than it has been over the past few days, it appears these storms will take a more southerly route E/SE across the heart of central Illinois. CAMs exhibit a high degree of variability, so confidence in the exact location/timing of the storms remains low. Given the prevailing synoptic pattern and a persistence forecast, think the 12z RRFS offers the most likely scenario...taking storms into the Illinois River Valley by late morning, then further east across the rest of the area during the afternoon.

The environment feeding into the storm complex will not be as unstable or sheared as today's scenario across northern Illinois. The 12z HREF suggests ensemble mean SBCAPEs of 2000-2500J/kg (rather than the 3000-4000J/kg from today), while the GFS/NAM generally show 0-6km bulk shear of 25-35kt. These parameters are certainly supportive of strong to severe convection: however, am not anticipating the same magnitude of today's storms to the north. Instead think damaging wind gusts of 60-70mph, hail larger than quarters, and isolated tornadoes will be the main hazards.

**** Additional Storm Chances Through Friday ****

The latest SPC Day 3 Convective Outlook highlights central Illinois with a Marginal Risk (level 1 of 5) on Thursday. With the boundary still wavering in the immediate vicinity, additional storm clusters will form and track across the region Wednesday night through Thursday night. Given an overall decrease in deep-layer shear, the severe risk will gradually wane as well. Gusty winds, hail, and locally heavy downpours will be likely on Thursday. After that, the prevailing upper ridge currently centered over the Desert Southwest will shift into the lower Mississippi River Valley by the end of the week. With rising upper heights, the surface frontal boundary will get shunted back northward and storm chances will decrease by Friday and Saturday.

AVIATION /06Z TAFS THROUGH 06Z THURSDAY/

Issued at 1216 AM CDT Wed Aug 12 2026

Near-term guidance continues to show a thunderstorm complex moving through parts or all of central IL from late Wednesday morning into the afternoon hours. Because large uncertainty in storm coverage exists, held onto the PROB30 groups at all terminals for this cycle. Outside of this, patchy MVFR fog could develop early this morning, favoring areas near and north of I-74. 8-10 kt southwest winds will be in place most of the period, becoming sporadic with any storms, then becoming east-southeasterly and light by Wednesday evening.

ILX WATCHES/WARNINGS/ADVISORIES

None.