textproduct: Chicago

KEY MESSAGES

- Showers and thunderstorms are expected through midday, with highest chances along and east of I-55. Primary concern is downpours leading to ponding in poor drainage areas.

- Above normal temperatures through the early part of the week, though cooler near Lake Michigan.

DISCUSSION

Issued at 226 AM CDT Sun May 24 2026

Festering showers continue to bubble up west of the forecast area, closer to a surface front analyzed along or just west of the Mississippi River. With weaker forcing, coverage is a little lacking leading to more isolated to localized clusters developing. A few lightning strikes may be possible, but with limited instability, confidence low. Some of these showers may continue into the area west of the Fox Valley through the next couple of hours.

The previously mentioned front is expected to sweep across the area through the early morning, exiting to the east around midday. Coverage of showers along and ahead of the front is expected to increase closer to daybreak along the better forcing with the arrival of a mid level wave. Southerly winds will advect in an almost tropical air mass with precipitable water amounts north of 1.50 inches. With slow storm motions (around 20 mph or less) nearly parallel to the front, the primary threat is for downpours and even localized torrential rainfall. Widespread flash flooding is not expected, but with intense rain rates (locally greater than an inch per hour) and possible training there is a chance that there could be localized ponding in poor drainage areas. Additionally, model soundings depicting tall, skinny CAPE allows for the potential for some embedded thunder as the front moves through, though higher coverage of storms is expected along and east of I-55 after daybreak.

Drier conditions are expected in the afternoon in the wake of the front through Tuesday. Models are suggesting a weak 700 mb wave moving across Iowa into lower southern Wisconsin late on Monday. Given its projected track away from northern Illinois, PoPs were kept dry and just something to monitor. Otherwise, upper level ridging and surface high pressure will grow today through Tuesday driving not just dry conditions but warm, above normal temperatures. Lake breezes will help keep cooler conditions cooler near the lake shoreline, but temperatures well into the 80s can be expected farther inland.

Models are suggesting that by Wednesday morning, a near Omega blocking pattern will set up in the mid-to-upper levels. Ensembles are still suggesting that a weak 700 mb wave will move northward from the Gulf to the mid Mississippi River Valley. This could provide the next chances for rain and storms, but models noticeably keep the better chances farther south compared to 24 hours prior. As the stagnant pattern remains toward the end of the week, conditions are looking dry and seasonable beyond Thursday.

DK

AVIATION /12Z TAFS THROUGH 18Z MONDAY/

Issued at 700 AM CDT Sun May 24 2026

Key aviation forecast messages:

- SHRA with embedded TS ending from NW to SE through mid to late morning.

- Lake breeze turns winds east at the Chicago terminals this afternoon

Showers with a narrow band of heavy thunderstorms continues to progress east across the area this morning. These storms have been fairly progressive and accordingly moved up the end time of the TEMPOs for TSRA and the associated VSBY and CIG reductions with VCTS maintained for another hour or so within the stratiform rain though lightning coverage has trended down over the past 30 minutes or so. Lingering showers then end from northwest to southeast by late morning with dry conditions expected through the end of the period.

Wind directions will settle into a prevailing northwest direction in the wake of the showers/storms this morning with a lake breeze expected to turn winds east at the Chicago area terminals during the afternoon. Winds then turn southeast this evening and southwest by early Monday morning.

Similar to yesterday, given increased low-level moisture in the wake of this morning's showers and storms, we will have to monitor fog and low ceiling trends over Lake Michigan into the evening and early overnight hours in case it happens to ooze inland again.

Petr

LOT WATCHES/WARNINGS/ADVISORIES

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