textproduct: Central Illinois

KEY MESSAGES

- Showers and storms are likely this evening into tonight, primarily east of the IL River. The best chance for rainfall totals over a half inch is near and south of I-70 (60-80% chance). Severe storms are not expected.

- Below normal temperatures persist through Saturday. Frost is possible Friday night into early Saturday morning as lows fall into the mid 30s.

DISCUSSION

Issued at 125 PM CDT Tue Apr 28 2026

Current analysis shows a shortwave currently over the Mid- Missouri Valley, progged to track into central Illinois tonight. High- resolution guidance (HRRR/RAP) indicates rain showers will overspread the area from west to east after 00z. The HREF denotes a high probability (90%+) of rainfall totals exceeding 0.10 inches south of I-72, with localized amounts of 0.50-1.00 inches in southeast Illinois where better moisture convergence resides. Higher probabilities of thunder also exist south of I-70 where some elevated instability will be present. While we do not expect severe storms in the local area, SPC's marginal and slight risk areas are just to the south in southern IL.

Winds will shift to northerly behind the wave by Wednesday morning, with gusts reaching 20-25 mph. The cold advection will result in another cool day with highs in the low to mid 60s.

A deep upper- level trough remains anchored over the eastern half of the CONUS into this weekend. Strong cold air advection will suppress high temperatures into the 50s to low 60s, which is roughly 10-15 degrees below climatological norms. Dry conditions will dominate, with the exception of a fast- moving but moisture- starved shortwave crossing the region Thursday night. Will stick with NBM's 10-20% chance of showers for this period.

The primary concern late this week is the potential for frost late Friday night into Saturday morning. High pressure is forecast to settle over the Mid- Mississippi Valley, leading to clearing skies and diminishing winds. The ECMWF EFI shows a significant signal for anomalous cold, and NBM 10th percentile temperatures suggest lows in the lower 30s are feasible in rural and low- lying areas. High confidence (70-80%) exists in seeing frost across much of central Illinois during this time. Those with sensitive vegetation may need to take protective action.

Sunday through Tuesday... Rain chances return for Monday and Tuesday, though specific timing remains low confidence due to the variance in ensemble clusters. There is a better signal for temperatures rebounding to seasonable levels early next week across a range of guidance, supported by rising mid level heights.

AVIATION /00Z TAFS THROUGH 00Z THURSDAY/

Issued at 649 PM CDT Tue Apr 28 2026

VFR conditions will prevail at all TAF sites next 24hrs, except when showers are occurring at the sites, then MVFR cigs may occur at times.. Will have PROB30 groups at all sites for best chance of precip onsite. PIA will be from 03-05z, BMI from 03-08z, SPI from 02-08z, DEC from 03-09z, and CMI from 04-10z. At each site the light showers may start a little earlier and last a little later, but not change in cloud heights from predominate. Clouds will remain broken for some time after precip ends, but then scatter out in the afternoon. Winds will be light to start and then become northerly after the precip. Then expect winds to become northwest in the afternoon with speeds of 10-16kts.

ILX WATCHES/WARNINGS/ADVISORIES

None.