textproduct: Chicago

KEY MESSAGES

- Isolated sprinkles possible early this morning, otherwise mostly cloud, breezy and dry conditions expected today.

- Generally slightly below to below average temperatures expected into at least the first part of the upcoming weekend.

DISCUSSION

Issued at 158 AM CDT Wed Sep 23 2026

Looping the regional radar mosaic since last evening indicates that the mid-level vort associated with an upper-level low was centered just west-southwest of Chicago early this morning. This feature appears to be becoming more sheared in response to a stronger mid- level short wave tracking southeast from southern IA into northeast MO and west-central IL. Isolated/widely scattered showers beneath the center of the original vort have dissipated over the last few hours, though have maintained some decreasing slight chance (15-20%) pops near the center of the circulation during the predawn hours in case anything redevelops. Can't completely rule out some isolated sprinkles or even patchy drizzle across the east/southeast parts of the cwa this morning as the shearing vort continues to drift slowly off to the east-southeast, though rather shallow moisture profiles in forecast soundings indicate little substantial precip threat. Extensive (but shallow) low-level cloud deck was noted in GOES imagery spreading westward across the forecast area however, and this should maintain cloudy/mostly cloudy skies across the area today, especially across the southern half/two thirds of the area. Cloud cover and still-breezy northeast winds will keep temperatures on the cool side once again, with highs in the mid-60s for most areas.

With our mid-level short-wave energy slowly tracking off to the southeast of the region though the end of the week, we'll see upper ridging develop into the western Great Lakes region (though tempered by the passage of a mid-level short wave along the U.S.Canadian border Thursday night into Friday). This will allow the western periphery of the elongated surface ridge to our north settle across the area, and will maintain dry and seasonably cool weather conditions along with diminishing winds for the local area.

Evolution of a deep cut-off low along the east coast by the weekend will tend to set up a blocky upper-air pattern across the eastern CONUS, preventing much in the way of significant precipitation chances for the forecast area. Guidance does depict another more amplified short-wave propagating into the upper Midwest this weekend, with the potential for a (likely) decaying area of precip to approach the forecast area late Saturday night/early Sunday. This wave will be pushing into the upper ridge and fighting drier low- level air, however. Global ensemble pops remain focused the Mississippi River through the weekend. The NBM initialized with some low-chance pops across our western cwa late Saturday night/early and made no changes, though it doesn't look like a significant rain threat for the daytime weekend hours. A gradual modest warm-up back to average temps (low/mid 70s) is expected later in the weekend into early next week. Extended guidance/ensembles eventually eject the deep east coast cut-off low off to the northeast Monday/Tuesday, with the next chance of any significant precip likely holding off until the middle of next week.

Ratzer

AVIATION /18Z TAFS THROUGH 00Z FRIDAY/

Issued at 1239 PM CDT Wed Sep 23 2026

Cloudiness will continue to rotate counter-clockwise around an upper level low located over the Ohio Valley. While there will be occasional breaks, this cloudiness will generally result in a BKN VFR deck at the terminals. There are pockets of MVFR CIGS embedded within the broader BKN VFR deck and there could be occasional MVFR CIGS at the terminals today into tonight. For now, just included a TEMPO for MVFR CIGS for the first 4 hours of the TAF, but it is possible that additional TEMPOs or even a period of prevailing MVFR may be needed with later updates.

Otherwise, look for east to northeast winds to continue through the TAF cycle at the terminals. There could be a few sporadic gusts to around 20kt this afternoon. Winds will ease a bit after sunset.

- Izzi

LOT WATCHES/WARNINGS/ADVISORIES

IL...Beach Hazards Statement through Thursday morning for ILZ006.

Beach Hazards Statement until 10 PM CDT this evening for ILZ103-ILZ104.

IN...None. LM...Small Craft Advisory until 10 PM CDT this evening for the IL nearshore waters.