textproduct: Central Illinois

KEY MESSAGES

- Periods of showers and a few thunderstorms are expected this morning, then again later this afternoon into the overnight hours. Damaging winds, heavy rain, and localized flooding is in play today. - A persistent northwest flow will keep temperatures and humidity levels in check the next several days, with highs in the upper 70s to lower 80s.

DISCUSSION

Issued at 211 AM CDT Wed Aug 19 2026

Today will be a brief return to the active weather. The CAMs are showing a narrow band of showers and/or thunderstorms setting up in a west-east orientation across central IL, potentially where the flooding and heavy rain occurred last week. Timing looks to be mid afternoon for this band (20z Weds to 06z Thu). WPC has introduced a slight risk ERO for today for all of ILX CWA. PWATs won't be as high as they were last week, but forecast soundings are suggesting 1.7- 2.0 inch values in place. Those same soundings have a long, skinny CAPE profile. LPMM shows pockets of 2-5 inches locally in the vicinity of the band. A Flood Watch will be in effect from 18z today to 06z tonight for the northern half of the CWA.

Along with that narrow band, there could be a convective complex that moves south of I-72, with the greatest severe risk in southern IL. There is some uncertainty on if the complex will reach as far north as I-72. The HRRR (00z) is the most bullish, with the complex riding along and south of I-72 from 00z-08z this evening/overnight. The 00z NAMNest is the opposite, depicting a much drier, less active solution. The 00z RRFS agrees on the west-east oriented line setting up in central IL but has the later complex missing the CWA off to the south in southern IL. SPC has a marginal risk for severe weather in place for areas along and south of I-74 for the activity later today with damaging winds as the main threat.

Thursday is looking to be dry and quite pleasant. Then, additional chances for rain return Friday into Saturday. A dry start to the new week as a high pressure develops over the Great Lakes region Sunday. Most people will likely remain dry or see minimal rainfall amounts after today for the extended forecast. Pleasant August temperatures are in store for the next week, with upper 70s to 80s for highs and 60s for lows.

AVIATION /06Z TAFS THROUGH 06Z THURSDAY/

Issued at 1155 PM CDT Tue Aug 18 2026

Convection is expected to pass southwest of central IL tonight, providing an increase in high clouds. The next wave is progged for Wed afternoon and evening and this looks to be more focused over the central IL terminals. Kept PROB30 TSRA mention for all sites as coverage and location is still low-medium confidence, but if current trends hold TEMPO and predominant groups will be added later. Otherwise, a BKN MVFR stratocu deck looks to develop over the area Wed morning, lifting to VFR during early to mid afternoon.

ILX WATCHES/WARNINGS/ADVISORIES

None.