textproduct: Central Illinois

KEY MESSAGES

- Showers and a few thunderstorms will track across the eastern half of central Illinois today. Severe weather is not expected.

- After a quiet weekend, the next significant risk for strong to severe thunderstorms will arrive by Monday. At this time, it appears all severe hazards will be possible Monday afternoon and evening as a potent storm system lifts through the region.

UPDATE

Issued at 1027 AM CDT Fri Apr 24 2026

Showers with a threat of a few thunderstorms will continue east of I-55 into the afternoon as a cold front works its way across the area today, combined with a shortwave promoting widespread showers from southwest to east-central IL this morning. Have increased PoPs to likely category in east-central IL through mid afternoon for this feature, and decreased highs a couple of degrees in anticipation that the widespread cloud cover will limit diurnal temperature increases. Still, a relatively warm day for April is on track with highs in the lower to mid 70s.

DISCUSSION

Issued at 325 AM CDT Fri Apr 24 2026

*** Lingering Showers Today ***

07z/2am surface analysis shows a cold front extending from northern Wisconsin southwestward to Oklahoma. A broken line of convection is currently ongoing well ahead of the boundary: however, it has undergone considerable diurnal weakening and no longer poses a severe weather risk as it spills eastward into the Illinois River Valley. Will need to keep an eye on some of the stronger cells for the next couple of hours as they could potentially produce gusty winds. The main line will reach the I-55 corridor by 3-4am and I-57 by 5-6am. Once the initial line weakens and/or pushes eastward into Indiana, a lull in precipitation chances will be observed before modest re- development along/ahead of the advancing front this afternoon. Most CAMs suggest the bulk of the afternoon showers will form east of I-55, then will quickly exit the eastern KILX CWA toward sunset.

*** Pleasant Weekend Ahead ***

Once the cold front departs, high pressure will build into the Great Lakes and provide a cooler/drier E/NE boundary layer flow this weekend. As a result, am expecting afternoon highs in the lower to middle 70s and overnight lows in the middle to upper 40s. Abundant sunshine will be the rule on Saturday, followed by a gradual increase in cloudiness by Sunday afternoon.

*** Severe Weather Risk Monday ***

As has been advertised by the past several model cycles, the next significant storm system to impact the Midwest is slated to arrive on Monday as a vigorous short-wave trough evident on the latest water vapor imagery over the central Pacific comes onshore across southern California late Saturday...then lifts northeastward into the Upper Midwest by Monday. As the negatively tilted upper trough approaches, a deepening surface low will track from the southern Plains Sunday night to the western Great Lakes by Monday night. The exact track of the low remains somewhat in question...with the 00z Apr 24 GFS being slightly further S/SE with the track as compared to the ECMWF/GEM. All solutions suggest elevated convection developing along/north of the attendant warm front across central Illinois late Sunday night into Monday morning. This early day convection will initially limit surface-based instability: however, all models indicate the warm front will surge northward into the southern Great Lakes during the afternoon. The 00z GFS shows a highly unstable/sheared environment within the warm sector as surface dewpoints climb into the 65-70F range. Corresponding SBCAPEs reach 2500-3500J/kg along/south of I-74 by 21z Monday while 0-6km bulk shear ranges from 45-55kt. Given these parameters and the proximity of the surface low over Iowa/Wisconsin by late afternoon, supercell thunderstorms will be likely...with all severe hazards in play. Current Day 5 Convective Outlook from SPC highlights locations along/south of a Rushville to Mattoon line with a greater than 30% chance for severe weather...but think this risk area will be pulled further northward with subsequent issuances. Stay tuned to later forecasts for more details.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1252 PM CDT Fri Apr 24 2026

SHRA near a cold front will continue to affect KDEC-KCMI eastward the first few hours of the period, then dry conditions will ensue. Isolated MVFR cigs possible in this precipitation. Scattered diurnal cumulus will develop in the afternoon, with occasional MVFR cigs. By 20Z-23Z, VFR conditions are expected. Winds turning from SW ahead of the front to NW this afternoon, then gradually veering to NE overnight, with wind speeds generally under 12 kts.

ILX WATCHES/WARNINGS/ADVISORIES

None.