textproduct: Central Illinois

KEY MESSAGES

- There is a Marginal Risk to the IL/IN border and a Slight Risk in place for areas southwest of a Macomb-Havana- Taylorville line. The primary threat today is damaging wind gusts of 60 mph. Timing mid afternoon into evening.

- Periods of heavy rain will spread across the area between Friday and Saturday. Slow-moving thunderstorms Friday night into Saturday morning will increase the risk for localized flash flooding over saturated ground. Total rainfall will average 1 to 2 inches across central Illinois, though localized spots could see 3 to 4+ inches where heavy rain bands repeat.

- Outside of thunderstorms Saturday, winds will be quite gusty. The HREF shows a 70-100% chance of wind gusts greater than 35 mph west of I-55 during the afternoon and evening hours.

DISCUSSION

Issued at 200 AM CDT Fri Jul 31 2026

An active weather pattern returns today as a low pressure system moves through the central part of the United States today and tomorrow. Showers and thunderstorms will be pushing through central and southeastern IL the next few days in multiple waves. The next few days won't be a complete washout as there will be breaks in the rainfall. There will be a dry slot that will push into the area overnight tonight into tomorrow morning, before additional storms develop tomorrow morning. Outside of any storms, skies will be cloudy.

Our main concern with this system is the heavy rain potential. The first wave will enter western IL by 12-13z this morning. Between 12z this morning and 12z Sunday, we are forecasting 1-2.5 inches of rainfall. The greatest probabilities of rainfall amounts exceeding 2 inches is north of I-72. The greatest rainfall amounts won't be widespread and fairly localized. Some localized areas could see 4-7 inches of rain based off the 00z HREF LPMM accumulated precipitation. WPC has us in a slight risk ERO for today and a marginal risk for tomorrow. Flash flooding could occur where grounds are already saturated or after multiple rounds of heavy rain over the same locations.

The SPC just expanded the severe threat for today to encompass our entire forecast area with Marginal Risk to the IL/IN border and a Slight Risk in place for areas southwest of a Macomb-Havana- Taylorville line. The primary threat today is damaging wind gusts of 60 mph. MUCAPE will be highest in the slight risk area with values of 1000-2000 J/kg mid to late afternoon today. The shear values are around 30-40 knots.

The severe threat goes down overnight into Saturday, but MUCAPE value will remain ~1000 J/kg into Saturday. SPC does not have us outlooked at this time for Saturday. Although, a 2% tornado threat could be introduced potentially. The low pressure center will move directly overhead on Saturday, increasing the non-supercell tornado parameter. Even if the low tornado chance doesn't pan out, someone may see a funnel cloud(s) across central IL. Outside of thunderstorms, winds will be quite gusty. The HREF shows a 70-100% chance of wind gusts greater than 35 mph west of I-55 during the afternoon and evening hours.

Temperatures will cool off today into Sunday with highs in the mid 70s to low 80s. Temperatures gradually increase solidly back into the 80s, nearing 90 degrees by Friday next week. Lows will be in the 60s for the next week before warming to around 70 degrees by Thursday night.

Weather will dry out for Monday, but additional rain chances muddle the new week starting Tuesday. There are low (~20%) chance for rain off and on throughout next week.

AVIATION /12Z TAFS THROUGH 12Z SATURDAY/

Issued at 601 AM CDT Fri Jul 31 2026

Deteriorating conditions are expected as a low pressure system brings waves of showers and storms beginning 15z-18z. MVFR cigs/vsbys are anticipated by 15z-18z from SPI-BMI and northwestward, perhaps eventually reaching IFR especially near PIA. At DEC-CMI, primarily VFR cigs with periods of MVFR vsby are expected. IFR cigs are likely to spread across the entire area after 09Z Saturday. Winds increasing to SSE 12-15 kts with gusts 20-25 kts by 16z.

ILX WATCHES/WARNINGS/ADVISORIES

None.