textproduct: Central Illinois

KEY MESSAGES

- There is a Marginal Risk (level 1 of 5) for severe weather along and east of I-57 this afternoon.

- Blustery and colder conditions are expected for Thursday and Friday as high temperatures dip below normal into the 40s.

DISCUSSION

Issued at 247 AM CST Wed Nov 11 2026

**** Severe Weather Risk This Afternoon ****

A 1012mb low analyzed over western Iowa at 08z/2am will gradually deepen as it tracks E/SE across central Illinois today. Scattered showers are currently ongoing north of the system...and this trend will continue through midday. As a result, have confined morning PoPs to locations north of I-72. The 00z KILX upper air sounding featured precipitable water of just 0.48: however, both the HRRR and RRFS show values increasing into the 0.75-1.00 range ahead of the approaching low. Given the uptick in moisture, REFS mean SBCAPEs increase to 500-1000J/kg east of the I-55 corridor this afternoon. With adequate moisture and strong kinematic fields in play, it appears scattered thunderstorms will develop across the E/SE KILX CWA later today. While instability increases, storm relative helicity does as well...but does not reach maximum values of 100-150m2/s2 until just east of the Wabash River late in the afternoon. The most recent Day 1 SPC Convective Outlook features a 5-15% chance of severe wind/hail along/east of I-57...but keeps the 2-5% tornado risk further east along/east of the Wabash River in line with where the strongest instability/helicity will likely coexist. Think a few gusty thunderstorms capable of producing marginally severe winds will develop across the E/SE between 1pm and 5pm...then quickly push eastward into Indiana toward sunset.

**** End of Week Cool-Down ****

Once the low tracks into the Ohio River Valley, winds will veer to northerly and temperatures will begin to fall Wednesday night as overnight lows drop into the upper 30s and lower 40s. As a short-wave trough noted on the latest water vapor imagery over northern Manitoba/Ontario dives southward and re-enforces the long-wave trough east of the Mississippi River, it will provide sufficient lift to trigger scattered light showers on Thursday. Thanks to ample cloud cover and strong CAA, high temperatures will remain in the middle to upper 40s across much of the CWA...with lower 50s confined to locations along/south of I-70. The current forecast features northerly wind gusts of 20-25mph: however, the 00z NBM hints that even higher gusts will be possible...with a 20-30% chance of gusts greater than 30mph. The strong winds will make it feel even cooler, as wind-chill values hover in the 30s for much of the day.

Will still need to keep an eye on a band of lake-enhanced showers from Lake Michigan: however, the boundary layer fetch should generally keep it E/NE of central Illinois across northeast Illinois into north-central Indiana Thursday night into Friday. Despite a return to partial sunshine, Friday will be the coolest day of the forecast period as highs only reach the lower to middle 40s. As high pressure builds into the region, skies will clear and winds will become nearly calm over the weekend. The end result will be cool days with highs in the 40s and overnight lows in the 20s. After that, the dominant upper trough will gradually shift E/NE away from the region and heights will rise next week. This will allow temperatures to moderate back to near or slightly above normal in the middle to upper 50s by next Wednesday.

AVIATION /06Z TAFS THROUGH 06Z THURSDAY/

Issued at 1026 PM CST Tue Nov 10 2026

A low pressure system will track southeast across central IL on Wednesday afternoon. This will bring scattered TSRA to the area, though low coverage is expected, so kept mention to PROB30 for -TSRA and brief MVFR conditions at all terminals except for KSPI (storms should stay to their northeast). Light/variable winds tonight will increase from the southwest ahead of the low on Wed morning, then northwest during the afternoon. Gusts up to 25 kt are expected behind the low for the late afternoon, with a gradual diminishing trend during the evening.

ILX WATCHES/WARNINGS/ADVISORIES

None.