textproduct: Central Illinois

KEY MESSAGES

- Rain showers overnight will be most numerous east of I-55, but amounts will be low.

- While another period of showers is expected late Saturday night into Sunday, the Memorial Day holiday is likely to be dry.

- A warmer weather pattern begins tomorrow and persists through next week, with high temperatures in the 80s common.

DISCUSSION

Issued at 140 PM CDT Fri May 22 2026

A shortwave continues to lift out of northeast Arkansas early this afternoon, and should move into southeast Illinois by mid evening. While rain has been minimal in our area thus far, some showers have recently developed near and northwest of Effingham. The more substantial rain chances will spread over southeast Illinois later this afternoon, remaining in the 60-70% range east of I-57 into the evening. This still does not look to be a generous rain producer, with less than a tenth of an inch expected. West of I-55, dry but cloudy weather should prevail overnight.

As the shortwave pulls away Saturday morning, some breaks in the clouds begin to develop. However, another wave across the Plains will move eastward, reaching the Mississippi River early Sunday. Currently thinking most of the day should be dry in our area, but a few showers ahead of the wave may sneak into the Illinois River Valley by late afternoon. Highest rain chances with this wave still appear to be late Saturday night through Sunday morning.

Going into early next week, upper level ridging begins to amplify just east of the Rockies on Memorial Day, gradually forming into an omega block pattern by mid week with upper lows in the vicinity of California and northern New England. Temperatures reach the mid 80s over areas west of I-55 by Memorial Day, and highs in the 80s should be fairly common much of the week, though humidity levels will not be overly excessive. Global models show periods of showers and storms across the mid Mississippi Valley, associated with a weak disturbance over the central and southern Plains. However, with an easterly wind flow around high pressure in Ontario, the northern extent of this rain is uncertain. NBM guidance is fairly high mid week (50-60%), but is reasonable with the uncertainty at this time.

AVIATION /00Z TAFS THROUGH 00Z SUNDAY/

Issued at 551 PM CDT Fri May 22 2026

MVFR ceilings have been intermittent across the central IL terminals late this afternoon. Trends this evening favor sites falling solidly into MVFR, with KPIA likely the last to drop after 06z. Probabilities of IFR ceilings are highest at KCMI overnight with medium probs at KDEC. These two sites will have the best chance of seeing a shower, though with very low coverage kept mention to VCSH. A gradual rise in ceilings is forecast Saturday morning, and most sites should return to VFR conditions during the afternoon. Winds will generally be under 10 kt through the forecast. A period of light/variable winds is likely overnight as a ridge moves overhead, then southwest winds develop behind the ridge Sat afternoon.

ILX WATCHES/WARNINGS/ADVISORIES

None.