textproduct: Central Illinois

KEY MESSAGES

- Intermittent chances for showers and thunderstorms resume Wednesday and continue through the weekend, though the majority of the time likely be dry.

- After a cool start to the work week, temperatures will moderate to generally near average by the middle-end of the week.

DISCUSSION

Issued at 122 PM CDT Mon Jun 22 2026

Stratus deck has been stubbornly slow to clear this afternoon, especially over southern CWA, leading to fairly cool temperatures for the first full day of summer. Drier air, high sun angle, and mixing should continue to chip away at the stratus from NW to SE the rest of this afternoon. Opted to remain optimistic showing skies clearing out this evening given the time of year. The light winds, mostly clear skies, and dewpoints in the 50s should set the stage for a cool night. The dry air mass and sunny skies will allow for a quick rebound temps Tuesday.

Shortwave trough is progged to track from the northern Plains and southern Canada Tuesday into the western Great Lakes Wednesday. By Wednesday afternoon, the associated sfc low is forecast to be over Wisconsin with a weak cold front trailing south from the low into western Illinois. Moisture return in advance of this front is progged to be pretty meager and the strongest synoptic ascent looks to remain to the north of the area, but still can't rule out some scattered afternoon convection Wednesday, especially near/northwest of I-55 corridor.

As parent shortwave moves off to the east Wednesday night and Thursday a more zonal flow will set up across the Lower 48 late this week into the weekend. This should cause Wednesday's front to lose steam and likely stall out across the Ohio Valley. Low amplitude, difficult to predict disturbances rippling though this zonal flow will likely be the impetus for occasional MCS activity riding near and north of the quasi-stationary low level baroclinic zone.

GFS and ECMWF have both been hinting at one such convectively enhanced shortwave moving into the region Thursday night or Friday. There is considerable spread among the various GFES and EPS members with respect to timing and placement of the highest precip chances. Given the northward spread of deeper Gulf moisture northward, if a stronger convectively enhanced shortwave were to move through the region, heavy rainfall and even some threat of severe weather would exist. With low predictability for these type of systems this far out it is impossible to pin down any details, but the late week could turn more active again.

There is good agreement in medium range guidance in depicting an amplifying mid-upper level ridge over the Mississippi Valley. While MCS activity could temporarily delay the boundary from lifting northward, it looks like it should eventually get north of the area by early next week. This would suggest chances for more typical summertime heat and humidity building into the area will increase late in the weekend and particularly into early next week.

- Izzi (WFO LOT)

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 1200 AM CDT Tue Jun 23 2026

VFR conditions will prevail at all TAF sites next 24hrs. Skies will be clear through the night. Then CU is expected to develop again tomorrow but then dissipate in the early evening, followed by scattered high cirrus. Winds will be light through the period with a northerly direction during the day.

ILX WATCHES/WARNINGS/ADVISORIES

None.