textproduct: Central Illinois

KEY MESSAGES

- Above normal temperatures are likely to persist into mid June, with highs likely in the 80s over the next two weeks.

- There is a 20-30% chance of showers and thunderstorms over west central IL from Galesburg to Springfield west into early evening. There is a 30-50% chance for showers and thunderstorms storms from Peoria to Lawrenceville west overnight Sunday night into Monday, with chances highest southwest of Springfield.

DISCUSSION

Issued at 230 PM CDT Sat May 30 2026

The 19Z/2 pm surface analysis shows 1029 mb high pressure over James Bay Canada and ridging southward across the Great Lakes and into the Ohio river valley. Easterly flow of drier air over central and eastern IL with dewpoints in the upper 40s to mid 50s, while higher dewpoints in the upper 50s/lower 60s from Jacksonville to Taylorville to Effingham and Olney sw. Warm temps were in the low to mid 80s at 2 pm. Radar mosaic shows a narrow bands of showers west of a Monmouth to Havana to Jacksonville line drifting northward. Scattered showers and thunderstorms were over MO and into the St Louis metro area. More unstable air mass was over sw IL/MS river valley where MLCAPES are 500-1500 j/kg and PW values are 1.7-1.9 inches. We added 20-30% chances of showers and isolated thunderstorms into early evening along and west of a Galesburg to Springfield line. The isolated convection over west central IL should dissipate by dusk. Latest CAMs shows more convection developing over MO tonight and weakening as it drifts into west central IL later tonight into Sunday morning where air mass is more stable. Lows overnight 55-60F, coolest in east central IL. A bit cooler highs Sunday in the upper 70s/lower 80s with partly to mostly cloudy skies.

Convection chances to increase overnight Sunday night over central and westcentral with increase moisture spreading a bit further east into IL. Have 20-40% chance of convection lingering over central/sw CWA Monday. SPC Day3 has a marginal risk of severe storms Monday sw of a Macomb to Springfield to Flora line for damaging winds and hail being risks. Though more unstable air mass will remain over MO where better chance of storms will be. Highs Monday mostly in the lower 80s.

Another Canadian high pressure system drops down into the Great Lakes region from Hudson Bay on Mon night and Tue and into the southern Great Lakes, ohio river valley on Wed. This to bring drier more stable air back into central IL with dry weather during mid week. As large high pressure sprawls across the mid Atlantic States on Thursday will see SSW flow begin and start to bring warmer air back into the area, along with more humidity too especially Fri/Sat with dewpoints back into the 60s. This will return chances of convection to central IL Friday and central and southeast IL Fri night/Saturday.

The Climate Prediction Center (CPC) 8-14 Day Outlook for June 7-13th has 45-55% chance of above normal temperatures over central/se IL with precipitation trending near normal.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 1220 PM CDT Sat May 30 2026

VFR conditions expected through the period as a stalled frontal boundary lingers to the southwest and high pressure centered to the north keeps dry easterly flow in place over the area, preventing precipitation to the west from spreading eastward into the area. Expect a gradual increase in high and mid clouds through the period. Winds E 10-14 kts with a few higher gusts today, decreasing to 8-12 kts and shifting to ESE through the period.

ILX WATCHES/WARNINGS/ADVISORIES

None.