textproduct: Central Illinois

KEY MESSAGES

- Showers and a few thunderstorms will track across 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.

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 /12Z TAFS THROUGH 12Z SATURDAY/

Issued at 551 AM CDT Fri Apr 24 2026

A decaying band of showers will continue to shift E/NE across central Illinois early this morning...primarily along/east of I-55. Based on radar trends, have opted to carry predominant showers at all terminals except KPIA through 16z/17z. After that, showers and perhaps a couple thunderstorms will re-develop this afternoon east of the I-55 corridor. Areal coverage will remain low, so opted not to mention thunder at this time. Any lingering showers will push into Indiana toward sunset, followed by dry conditions through the remainder of the 12z TAF period. Ceilings will remain VFR: however, a narrow band of MVFR across Iowa/Missouri will try to spill into the Illinois River Valley this morning as per the HRRR. Think these clouds will remain W/NW of KPIA, but trends will have to be carefully monitored for potential amendments. As a cold front exits into the Ohio River Valley, skies will clear from west to east this evening. Winds will initially be SW at 10-15kt this morning, then will veer to NW after FROPA this afternoon. Winds will then drop to less than 10kt and veer to N/NE later tonight.

ILX WATCHES/WARNINGS/ADVISORIES

None.