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.

UPDATE

Issued at 914 PM CDT Tue Apr 28 2026

Some of the returns on radar across the northern part of the CWA is finally reaching the ground, but guessing most of it is not reaching the ground and is just virga. However, additional precip is still expected to develop and move across the area the remainder of the night, ending around morning. Any thunderstorms should remain to the southeast of I-72/Danville. Update should be coming shortly.

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 /06Z TAFS THROUGH 06Z THURSDAY/

Issued at 1208 AM CDT Wed Apr 29 2026

Scattered light showers are ongoing at the start of the period. These will end from west to east between 08-10z, and the rest of the period should be dry. While there is a low chance of MVFR ceilings with the showers, have not seen enough sfc obs of MVFR along and north of I-72 to support keeping it in the TEMPO groups. Thus, VFR is forecast to prevail through the period, along with northwest winds which could gust 20-25 kts during the afternoon.

ILX WATCHES/WARNINGS/ADVISORIES

None.