textproduct: Central Illinois

KEY MESSAGES

- Localized heavy rainfall early this will yield pockets of 1 to 3 inch totals near and south of I-70, leading to potential ponding in low-lying areas.

- The Climate Prediction Center (CPC) 6-10 day outlook indicates a 40-70% probability of above-normal temperatures across central Illinois September 15-19. Normal highs this time of year is in the low 80s and normal lows in the upper 50s.

DISCUSSION

Issued at 145 AM CDT Thu Sep 10 2026

Showers and thunderstorms are moving through this morning as the front has stalled out across the southern half of the state. This convection has expanded as the LLJ increased, currently over the southern half of IL. The heaviest rain should remain along and south of the I-70 corridor. There is a low risk for flash flooding across the southeast. This area can likely take quite a bit of rain before flooding becomes a major concern. The 6 hour FFG for the southeast is 3-5 inches and 3 hr FFG is 3-4 inches. PWATs in the area of the storms is 1.9-2.2 inches. Localized swaths of 1 to 3 inches are still possible (particularly south of I-70) as highlighted by the HREF LPMM. WPC has maintained a marginal risk ERO along and south of I-72. The activity should move out by early afternoon.

High pressure will build over the Great Lakes Friday. Then additional low-end chances exist for showers and thunderstorms through the weekend. The NBM has broad brushed 30-50% POPs through much of next week starting Tuesday as a cold front looks to be progged to move through Illinois and potentially stall out.

More seasonable temperatures will be in place today and tomorrow with warming temperatures through the weekend. Mid to late week next week is forecast to be near normal behind the cold frontal passage Tuesday. The Climate Prediction Center (CPC) 6-10 day outlook indicates a 40-70% probability of above-normal temperatures across central Illinois through September 19th. Normal highs this time of year is in the low 80s and normal lows in the upper 50s.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

Issued at 600 AM CDT Thu Sep 10 2026

BMI and PIA may see some fog this morning, potentially dropping visibilities down to 4SM and ceilings into IFR range. SPI, CMI, DEC may experience some MVFR ceilings this morning with the area of precipitation passing through, becoming VFR by mid afternoon today, or sooner, but went with a more pestimistic forecast. All sites should be VFR with light north winds after 20z through the rest of the period.

In addition, the KSPI-KCMI corridor will be more favored for rain showers and periods of thunderstorms through the morning, with PROB30 mentions for TSRA at SPI/DEC and SHRA at CMI. IFR ceilings are possible in the heavier shower/storms this morning.

ILX WATCHES/WARNINGS/ADVISORIES

None.