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 /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1208 PM CDT Fri May 22 2026

Fairly large expanse of MVFR ceilings are in place at midday, though some modest improvement is expected this afternoon from KBMI-KSPI west. However, ceilings should deteriorate early this evening as a storm system lifts northeast out of Arkansas. Latest HREF brings 60-80% chances of IFR conditions to about KDEC/KCMI after 06z, with ceilings below 2000 feet as far west as KSPI-KBMI. Most improvement is expected mid to late Saturday morning as the low pulls away.

Stiff east/northeast winds 10-15 knots will continue through sunset, before diminishing. Late in the period, more of a northwest winds is expected with the departure of the low.

ILX WATCHES/WARNINGS/ADVISORIES

None.