textproduct: Central Illinois

KEY MESSAGES

- Temperatures start off the week below normal, then trend above normal next weekend.

- Quiet weather will turn more active late this week.

UPDATE

Issued at 1037 AM CDT Mon Jun 22 2026

Stratus deck has been pretty locked in over much of the central and southern portions of the CWA this morning. Given the high sun angle, still seems likely that the stratus should gradually break up and erode this afternoon, but it's looking like it will be a slow process.

Given the expected slower clearing, have nudged up sky cover up in the grids, especially southern CWA today. The more cloudiness will likely keep temps a but cooler, so nudged temps down just a bit.

- Izzi (WFO LOT)

DISCUSSION

Issued at 131 AM CDT Mon Jun 22 2026

The mid-level trough axis responsible for recent severe storms and heavy rainfall is pivoting eastward into Indiana early this morning. Radar imagery and short range guidance indicate a steady diminishing trend for scattered showers and areas of drizzle over the northeast CWA prior to sunrise. Subsidence and dry advection behind the trough will take some time to scour out the low clouds, with these processes bringing clearing in from the northwest this afternoon. High temperatures will reflect the cloud trends, with mid-upper 70s in the northwest CWA, to lower 70s in east central and SE IL where clouds hang on longer. North to northeast gradient winds on the back side of the low will gust 15-25 mph, highest over our eastern counties this morning.

For tonight into Tuesday, surface high pressure builds across the Upper Midwest and Great Lakes region, producing mainly clear skies, seasonably low humidity, and light winds. Lows tonight will drop well into the 50s. Highs on Tuesday will recover into the upper 70s to around 80 as the core of the high passes to the east.

The extended period features an active, progressive pattern with two distinct weather systems crossing the Midwest. The first system arrives Wednesday as a northern stream shortwave drives a cold front into Illinois. Low level moisture return will push dewpoints into the low-mid 60s. However, deeper layer moisture is lacking and with generally weak forcing along the boundary, prospects for severe weather are quite low. NBM's advertised 30-50% PoPs, with scattered storms for the afternoon and evening look appropriate.

Ensemble guidance shows the front stalling over southern IL on Thursday, then slowly working back north across the region Thursday night into Saturday. While the exact speed of this process is still in question, model consensus indicates the most favorable period for rain will be from Friday into Saturday when several bouts of convection may develop along and north of the front. ML/AI products indicate a low (5-15%) risk of severe weather during this period. After the boundary lifts to our north, a return to more typical summertime heat and humidity is expected for Sunday into early next week. Latest NBM shows highs around 90 for Sunday and Monday, with dewpoints rising into the low/mid 70s.

AVIATION /12Z TAFS THROUGH 12Z TUESDAY/

Issued at 430 AM CDT Mon Jun 22 2026

Widespread IFR ceilings will gradually improve to MVFR levels around 14-16z. Further improvement is expected this afternoon with terminals returning to VFR from the northwest at 19-21z. NNE winds will remain gusty this morning near 20 kt. Gusts will decrease this afternoon as the gradient relaxes, then go light under 10 kt this evening when high pressure approaches from the north.

ILX WATCHES/WARNINGS/ADVISORIES

None.