textproduct: Chicago

KEY MESSAGES

- Chance of thunderstorms returns Wednesday, some possibly becoming strong in the afternoon. Periodic, but low, chances for storms then continue through the end of the week into the weekend.

- Turning hotter and more humid into early next week.

DISCUSSION

Issued at 229 AM CDT Tue Jun 23 2026

Another dry day is slated for today as surface high pressure shifts overhead. This will support another day of onshore northeasterly winds, albeit to a lighter magnitude than those observed on Monday. Overall, temperatures this afternoon look to be similar to those observed on Monday, with readings generally topping out in the upper 70s inland, and in the low 70s near the Lake Michigan shore.

With our weather remaining quiet today, attention will be turning to the next mid-level trough/low that will be shifting eastward across the Dakotas and southern Prairie Providences of Canada today. This feature, along with an associated surface low, will move across the western Great Lakes Wednesday into Thursday. As it does, we can expect our next good chance (50%+) for scattered showers and thunderstorms Wednesday into Wednesday evening. The exact timing of these showers and storms remains a bit unclear, though possibility exists for some remnant showers and storms to move eastward across southern WI and perhaps parts of northern IL as early as Wednesday morning. Thereafter, new scattered showers and thunderstorms appear favorable to develop in the afternoon and evening, likely in the vicinity of an approaching cold front.

The environment in which these afternoon thunderstorms develop looks to be amply sheared, owing to the presence of an enhanced belt of westerly mid-level flow (45-50 kt) moving out across the warm sector. Accordingly, a severe potential may accompany these afternoon thunderstorms, though this will depend largely on ample destabilization occurring in the wake of the morning activity. Currently, the SPC has much of southern WI and parts of northern IL highlighted in a level 1 of 5 severe threat for Wednesday, which appears appropriate given the kinematic environment. We will continue to monitor this potential. Otherwise, the storms are expected to end from west to east with the passage of the cold front Wednesday evening.

On Thursday into Friday, the surface cold front is expected to stall out and become west-to-east oriented across downstate IL and IN as the next surface low sets up across the southern Plains into the Ozarks. This front is likely to continue to be the main focus for additional shower and thunderstorm activity later this week, primarily to our south. However, we cannot rule out some shower and storm activity working back northward into areas south of I-80 with the next wave of low pressure tracking along the frontal boundary on Friday. Otherwise, temperatures across the area will continue to be a bit below average, with highs generally in 70s to around 80 (cooler near the lake) Thursday and Friday.

This weekend into next week, ensemble forecast guidance continues to be in good agreement with a larger scale weather pattern change taking place across the central part of the country. The main feature of this transitioning pattern is expected to be the development of a subtropical ridge right across the Mississippi Valley into the Great Lakes into early next week. Locally, this is expected to result in a turn towards hotter and more humid weather and an end to the below average conditions.

KJB

AVIATION /12Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 632 AM CDT Tue Jun 23 2026

There are no significant aviation forecast concerns for the current TAF period.

The presence of surface high pressure in the region will result in light winds through most of the TAF period, with the strongest winds today expected to be near 10 kts from a northeasterly to easterly direction this afternoon at the Chicago metro terminals behind a sharpening lake breeze. Winds will take on a southerly direction tomorrow morning and increase towards 10 kts again as a low pressure system approaches the area.

The approaching low pressure system and an associated upper- level disturbance will bring showers and storms to the area tomorrow. The better chances for this activity affecting the terminals will come just beyond the end time of the current TAF period during the afternoon and evening (and during the morning for RFD), so opted to keep the TAFs dry for now, but some sort of precipitation and/or storm mention will likely need to be added in forthcoming TAF packages. If the rain does indeed hold off through the end of the current TAF period, then VFR conditions should prevail through the TAF period.

Ogorek

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...None. LM...None.