textproduct: Central Illinois

KEY MESSAGES

- Smoke and Air Quality: Smoke from Upper Midwest and Canadian wildfires will persist across central Illinois today, bringing reduced air quality before southerly winds push the plume northward on Monday.

- Severe Weather Threat (Monday/Monday Night): Organized severe thunderstorms are expected to move into the area late Monday through Monday night. The greatest risk for severe weather will target portions of central Illinois north of I-70, with storms capable of producing damaging winds and locally heavy rainfall.

- Additional Storms Tuesday: A second round of severe thunderstorms is expected to develop ahead of a cold front over east-central and southeast Illinois Tuesday afternoon before conditions clear out.

DISCUSSION

Issued at 109 PM CDT Sun Jul 19 2026

Smoke and Air Quality... Canadian and Upper Midwest wildfire activity continues to produce a smoke plume across portions of the Great Lakes and Midwest. Current HRRR near-surface smoke guidance indicates the plume will remain across central Illinois through the day today. Conditions are expected to improve from the southwest through the day Monday as a front lifts back north across the region, with south/southwest winds overspreading the area and helping to shunt the smoke plume northward.

Severe Weather Outlook: Monday and Monday Night... On Monday, the frontal boundary will lift back north across the region, allowing a warm, moist south to southwest flow to overspread central Illinois. This return flow will push temperatures back into the upper 80s to lower 90s, with dew points reaching into the mid 70s. While the return of heat and moisture is expected to be slightly slower due to a surface ridge axis lingering over east central Illinois, destabilization will eventually occur.

Strong instability is forecast to develop over west central Illinois, with MLCAPE values projected to peak around 2500 J/kg Monday afternoon and evening across portions of the lower Illinois River Valley. Simultaneously, a jet stream digging across the Upper Midwest will facilitate a notable increase in deep layer shear. Seasonably strong 0-6km shear of 40-50kt will overspread portions of central Illinois, supporting an organized severe weather threat. Convective initiation is expected over the Upper Midwest Monday afternoon and evening in response to a shortwave trough. By mid to late evening, a strengthening low- level jet will aid in storm maintenance as activity propagates southeast along the instability gradient into central Illinois. Monday and Monday night currently present the best parameter space for severe thunderstorms and will be monitored closely.

Convection: Tuesday... Storms are expected to redevelop over portions of east central and southeast Illinois early Tuesday afternoon. These storms will maintain strong potential for severe weather as significant diurnal instability develops ahead of a trailing cold front, coincident with persistent, strong deep-layer shear, before activity clears the area.

Extended Forecast: Wednesday through the Weekend... The remainder of the work week, beginning Wednesday, will feature drier air and slightly below-normal temperatures. Under the influence of a strong Canadian High pressure system spreading southeast across the Midwest, temperatures will generally top out in the low to mid 80s, with no notable precipitation chances expected. A warming trend will commence next weekend as the surface ridge axis shifts to our east, allowing for a return of warmer southerly flow.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/

Issued at 614 PM CDT Sun Jul 19 2026

MVFR visibilities are expected to prevail into Monday morning, as the extensive smoke field remains in place. Visibility of 3-5SM will be common, though there has been some improvement for a time this afternoon from KGBG-KSPI westward. A more substantial improvement in visibility will take place from west to east, late Monday morning through the afternoon, as winds switch to the southwest and push the smoke out of the area.

ILX WATCHES/WARNINGS/ADVISORIES

Air Quality Alert until midnight CDT Monday night for ILZ027>031-036>038-040>057-061>063-066>068-071>073.