textproduct: Central Illinois

KEY MESSAGES

- No major storm systems are expected to impact the region over the next week. As a result, the severe weather risk across central Illinois will remain low (less than a 5% chance) through next Friday.

DISCUSSION

Issued at 304 AM CDT Sat May 23 2026

*** Showers and a Few Thunderstorms Tonight ***

A short-wave trough noted on 07z/2am water vapor imagery over Indiana will continue to track northeastward away from central Illinois early this morning. A few lingering showers will be possible along/east of the I-57 corridor through daybreak before dry conditions return due to synoptic subsidence in the wake of the departing wave. Skies will initially be cloudy this morning, but will become partly sunny during the afternoon as high temperatures top out in the middle to upper 70s. Meanwhile a second short-wave currently upstream across eastern Colorado will approach from the west by late afternoon. The airmass ahead of this feature will become weakly unstable with NAM SBCAPEs reaching 1000-1500J/kg west of the Illinois River after 21z/4pm. As occurred ahead of the wave last evening across Nebraska/Kansas, CAMs are showing a line of broken convection forming near the Mississippi River by late afternoon, then pushing eastward to near the I-55 corridor by midnight. Areal coverage of precip will initially remain low due to lack of sufficient deep-layer moisture, but will increase overnight as a weak LLJ adds additional moisture. Based on model consensus, have confined low PoPs (20-30% chance) to locations west of the Illinois River late this afternoon, then have increased PoPs to 40-50% everywhere tonight. Daytime instability will quickly wane after sunset: however, enough elevated instability will remain present to warrant isolated thunder through the night. Scattered showers will be ongoing along/east of the Illinois River Sunday morning, but will come to an end from west to east across the area during the afternoon. Despite the precip chances tonight into early Sunday, rainfall will remain light...generally ranging from 0.10 to 0.25 with a few isolated pockets in excess of 0.25.

*** Additional Rain Chances Next Week ***

After a dry day on Monday, the NBM spreads rain chances back into central Illinois from south to north beginning as early as Tuesday...then lingering through Friday. The 00z models are all in good agreement concerning the general synoptic set-up next week, featuring a potential blocking pattern with strengthening upper ridging over the Upper Midwest and a low over the Lower Mississippi River Valley. While models show showers/thunder gradually pivoting northward into at least parts of central Illinois, the exact northern extent remains in question as northerly flow between the ridge and another short-wave digging southward into New England sharpens. This may tend to suppress the southern wave and force its associated precip back southward as the week progresses. For now, the forecast is showery from Tuesday through Friday...but this may change if current trends persist. While rain is in the forecast next week, the lack of a strong system and overall weak instability/shear will prevent severe weather development throughout the entire forecast period. As a result, the latest machine learning algorithms feature little to no chance (less than a 5% chance) for severe weather across central Illinois through at least next Friday.

AVIATION /06Z TAFS THROUGH 06Z SUNDAY/

Issued at 350 AM CDT Sat May 23 2026

Ceilings will continue to be the primary forecast challenge with the 12z TAF issuance as cloud bases vary considerably across central Illinois early this morning. While MVFR ceilings prevail across the majority of the area, the latest satellite imagery and local obs indicate a large hole in the low cloud cover along a line from KRFD southward to near KAAA...including both KPIA/KBMI. The HRRR seems to have a decent handle on the current situation and shows ceilings lowering at KBMI over the next couple of hours, but perhaps remaining VFR at KPIA. HRRR/NAM forecast soundings then suggest ceilings will scatter and/or diurnally rise to low VFR everywhere toward midday. Dry weather is initially anticipated: however, an approaching trough will trigger isolated showers/thunder west of the Illinois River by late afternoon. Based on the 06z HRRR, have included VCSH at KPIA after 22z accordingly. All models increase the areal coverage of precip further east after dark, so have added a TEMPO group for showers and a return to MVFR ceilings at all terminals except KPIA between 08z and 12z. Winds will remain light and variable through the entire period.

ILX WATCHES/WARNINGS/ADVISORIES

None.