textproduct: Central Illinois

KEY MESSAGES

- Isolated Severe Storms through Thursday: Scattered thunderstorms late this afternoon through Thursday evening bring a threat of isolated damaging wind gusts and large hail. These hazards shift from central Illinois today to areas south of Interstate 70 on Thursday.

- Heavy Rainfall and Flooding: Multiple rounds of storms bring a heavy rainfall and flood threat from Thursday night through Friday night. There is a 75% chance that rainfall totals will exceed 2 inches for locations south of Interstate 72.

- Dangerous Heat Next Week: A prolonged period of oppressive heat and humidity builds into the region Sunday through Wednesday. High confidence exists that daily heat index values will consistently exceed 100 degrees across the entire area.

..Thursday: Frontal Progression Shifts Hazards South

Overnight and into Thursday, the surface cold front is projected to sag slowly southward through the forecast area. This spatial progression will compress the severe weather threat further south, restricting afternoon shower and thunderstorm potential primarily to areas along and south of the Interstate 70 corridor.

Because boundary layer conditions near this slow- moving frontal zone are expected to mirror today's environment, isolated strong to severe thunderstorms will remain possible. Close monitoring will be required for any robust cells capable of producing localized damaging wind gusts and large hail.

...Thursday Night through Friday Night: Rainfall & Flooding Threat...

By Thursday night, the surface front is anticipated to stall out between the Interstate 70 and Interstate 72 corridors as the primary upper-level forcing shifts toward the eastern Great Lakes. The forecast focus will quickly transition to a heavy rainfall and hydrologic threat along this stationary boundary. A train of multiple upper-level shortwaves and weak surface low-pressure systems will traverse the stalled front from Thursday night through Friday night, interacting with a deeply saturated tropical airmass.

Precipitation Totals: Latest NBM guidance indicates an impressive 75% chance of rainfall totals exceeding 2 inches by Saturday morning along a corridor extending from Pittsfield to Lawrenceville.

Hydrologic Context: Saturated antecedent soil conditions from recent active weather will maximize runoff potential, elevating flash flood and river flooding concerns.

Headlines: Given the high confidence in multi-round convective rainfall over vulnerable basins, a Flood Watch has been issued for areas south of I-72 from Thursday afternoon to Saturday afternoon.

...Saturday through Next Week: Building Heat Dome & Oppressive Humidity...

Precipitation chances will diminish significantly by Saturday afternoon as the synoptic pattern undergoes major amplification. A persistent and highly anomalous upper-level trough digging over western North America will trigger robust downstream rising heights, establishing a formidable heat dome directly across the Midwest.

Temperatures: Daily maximum temperatures will routinely reach the lower 90s starting Sunday.

Heat Indices: Combined with high ambient humidity and pooling boundary layer moisture, latest NBM guidance indicates that heat index values may consistently exceed 100F from Sunday through Wednesday of next week.

Headlines: This prolonged period of oppressive heat will likely necessitate a series of Excessive Heat Advisories or Warnings for the entire region heading into next week.

AVIATION /18Z TAFS THROUGH 18Z THURSDAY/

Issued at 1153 AM CDT Wed Jun 24 2026

The main aviation concern through this TAF cycle is the low potential for scattered showers and thunderstorms through late evening, associated with a weak cold front. Confidence and coverage remain low enough for a mere PROB30 mention, and probabilities become even lower overnight into Thursday morning.

ILX WATCHES/WARNINGS/ADVISORIES

Flood Watch from Thursday afternoon through Saturday afternoon for ILZ052-054-056-061>063-066>068-071>073.