textproduct: Chicago

KEY MESSAGES

- Dry and mild through Saturday before rain chances begin to increase later Sunday.

- Waves of heavy rain producing thunderstorms possible in the general region early to mid next week.

DISCUSSION

Issued at 209 PM CDT Fri Sep 11 2026

A slow-moving compact wave along an elongated trough from Arkansas to southern Indiana will drift northeastward across Indiana through tonight. Upper-level clouds associated with the trough will continue to filter northward over the area through tonight. Meanwhile, a cold will track across the area late Saturday morning through the afternoon under notable surface- based capping. Given a rather dry antecedent airmass north of the trough and ahead of the cold front and a lack of organized large-scale forcing, precip-free conditions are expected through Saturday. The only exception is for the potential for a few showers nearing/brushing the extreme southeast CWA (i.e. Benton County) late tonight.

A mid-level trough crossing the western Great Lakes will interact with the stalling cold front across central Illinois Sunday before ridging quickly builds northeastward Sunday night into Monday. Optimal mid-level jet placement over and to the northeast of the area in conjunction with broad low-level isentropic ascent over the frontal surface should yield several bands of rain and/or scattered showers with perhaps some embedded thunderstorms Sunday afternoon into Monday morning. Sufficient moisture will be a limiting factor for precip coverage and intensity, so at least some of the area will likely remain dry during this period.

An aforementioned cold front will lift back northward as a warm front Monday afternoon and night in response to a strong surface low crossing far south-central Canada. An associated occlusion with the system's cold front and existing warm front will ultimately lead to a stalled front near or over the forecast area Tuesday into Wednesday. Persistent low-level moisture advection within an airmass characterized by PWATS of 1.7 to as high as 2 inches will likely lead to several rounds of heavy rain/showers and convection in this corridor, with an increased flooding potential if multiple rounds of precip align over the same area. Continue to monitor for updates as the forecast location of any persistent rain corridor becomes more refined.

The front will attempt to shift south late in the week as high pressure builds southward across the Great Lakes region. Have maintained chance PoPs Thursday and Friday as the showers would likely continue over the area if the front struggles remains stalled or only drifts southward with time.

Kluber

AVIATION /18Z TAFS THROUGH 00Z SUNDAY/

Issued at 1226 PM CDT Fri Sep 11 2026

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

Expect westerly winds tomorrow with gusts approaching 20 kts at times between mid-morning and mid-afternoon as a cold front approaches the area from the northwest. Couldn't completely rule out some sprinkles along and out ahead of the front late in the TAF period, but the most likely scenario is that the terminals will remain dry through the current TAF cycle. VFR conditions will also prevail through tomorrow.

Ogorek

LOT WATCHES/WARNINGS/ADVISORIES

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