textproduct: Central Illinois

KEY MESSAGES

- Low impact weather will dominate the area through this weekend.

- Periodic chances for thunderstorms will occur next week near a slow moving frontal boundary. South of the front, hot and humid weather will prevail.

DISCUSSION

Issued at 1222 PM CDT Fri Sep 11 2026

Midday surface analysis indicated high pressure centered over the eastern Great Lakes with ridging extending west into northern and central IL. Aloft, water vapor imagery showed a mid level shortwave tracking northeast near the MO bootheel. This system will provide forcing for isolated/scattered showers and possibly a few storms tonight for parts of southeast to east- central IL.

The next system of interest is an area of low pressure currently over SD. As this shifts northeast on Saturday, it will push a cold front into IA. Ahead of the front, thermal ridging brings another warming trend with highs the upper 80s to around 90. The front looks to stall in a west-east fashion over central IL on Sunday, resulting in a large temperature gradient with highs in the upper 70s over the far northern CWA, to the lower 90s south of I-70. The forecast does carry low (20-30%) PoPs in the vicinity of the front, however, limited upper level support and warm temperatures aloft should act to limit shower and storm coverage.

A more active period of weather is projected across the Midwest for much of next week. A strong upper level ridge will be anchored over the lower Mississippi River Valley for much of the week. Farther north, the northern branch of the upper jet will supply a series of disturbances to the northern Plains and upper Midwest. This is forecast to produce numerous rounds of thunderstorms near or just to the north of central IL for several days, most likely Tuesday through Thursday. While moisture and upper level dynamics are projected to be not as strong as what we saw during the "ring of fire" pattern around a month ago, it appears there will be ingredients present for a few rounds of locally heavy rain and potential severe weather, though ML/AI severe outlooks generally point to a 5% or less daily risk. Temperature trends will be closely tied to the position of the front and associated convectively cooled outflow. This will likely result in a large north to south temperature gradient across the region, with areas south of the front flirting with daily afternoon heat indices near 100 degrees.

AVIATION /00Z TAFS THROUGH 00Z SUNDAY/

Issued at 624 PM CDT Fri Sep 11 2026

Surface high pressure will linger over the regional terminals tonight, keeping surface winds light. Winds will gradually shift south overnight, becoming southwest by Saturday morning. Ceilings and visibility are forecast to remain VFR through this TAF cycle, though a low (20%) chance for MVFR visibility exists wherever patchy fog develops overnight.

ILX WATCHES/WARNINGS/ADVISORIES

None.