textproduct: Central Illinois

KEY MESSAGES

- Quiet through Midday Tuesday: Expect stable conditions across Central Illinois with highs in the upper 60s to mid-70s and only occasional sprinkles.

- Warming Trend Midweek: Temperatures and humidity will rise Wednesday and Thursday, pushing high temperatures near 80F.

- Heavy Rain Potential Wednesday-Friday: The primary weather hazard arrives Wednesday through Friday as a system bringing tropical moisture moves in. There is a 20-40% chance for rainfall to exceed 2 inches across our area, which may lead to ponding of roadways and localized flooding.

DISCUSSION

Issued at 101 AM CDT Fri Sep 25 2026

Under the influence of a blocking high, Central Illinois will see stable conditions persist through midday Tuesday while a Nor'easter slowly moves along the Mid-Atlantic and New England coasts. High temperatures are expected to stay in the upper 60s to mid-70s, accompanied by occasional low clouds and a slight possibility of sprinkles.

By Tuesday evening, global deterministic models indicate the ridge will begin breaking down as a shortwave trough advances into the Four Corners region. Guidance predominantly suggests this feature will merge with the tropical remnants of Polo. If this scenario holds, deep southwesterly flow ahead of the system will spread across the Southern Plains and Mid-Mississippi Valley, bringing slightly higher temperatures and humidity for Wednesday and Thursday, with highs nearing 80F.

Light rain may develop as early as Tuesday evening within a zone of warm advection associated with a lifting warm front. However, the primary round of impactful precipitation is projected for Wednesday through Friday as the southwestern U.S. shortwave tracks across the Southern Plains and Mid-Mississippi Valley. Although severe weather parameters appear marginal, heavy rainfall remains a concern toward the end of next week as Polo undergoes extratropical transition across the mid- latitudes. Current NBM guidance highlights a 20-40% probability of rainfall exceeding 2 inches across our area from Wednesday morning to Friday morning.

AVIATION /12Z TAFS THROUGH 12Z SATURDAY/

Issued at 453 AM CDT Fri Sep 25 2026

Multiple ceiling heights will be common through about midday. VFR will be the most common as high-based stratus continues to overspread the regional terminals this morning, though patchy MVFR ceilings will occasionally advect westward across the terminals beneath these high clouds. Have opted to go with TEMPO groups for the occasional lower ceilings.

Otherwise, surface winds will remain from the east/northeast throughout this TAF cycle, often between 5-10 kts.

ILX WATCHES/WARNINGS/ADVISORIES

None.