textproduct: Chicago

KEY MESSAGES

- A few showers may graze the US-24 corridor tonight and tomorrow morning.

- Dry weather with seasonable temperatures expected to end the work week.

DISCUSSION

Issued at 101 PM CDT Wed Sep 9 2026

Showers continue to taper in coverage across the area this afternoon in the wake of expansive composite outflow racing southward toward southern Illinois and Missouri. Gradual clearing of clouds has commenced allowing for temperatures to finally begin rising this afternoon. The expectation remains for highs to reach the mid to upper 70s before gradually falling after sunset. A few sprinkles may continue from time to time south of I-80 and especially US-24 through the evening.

Another shortwave over the central Rockies is expected to shear rapidly eastward into the lower Missouri River Valley later tonight and into tomorrow likely resulting in an uptick in coverage of showers and thunderstorms over Missouri. As this activity pushes east into Illinois, it is possible that the northern flanks of the showers could scrape across our far southern CWA late tonight into Thursday morning but the vast majority of this rain and all of the associated thunderstorm activity should stay south of our area.

By Thursday night, the center of the high pressure ridge should set up over the area. This should set the stage for nearly ideal radiational cooling with clear skies and calm winds. Have nudged low temps downward Thursday night, especially in the typical cool spots where lows could dip into the 40s. The urban heat island should keep the heat of the city of Chicago in the lower 60s for low temps. Can envision areas of shallow fog developing by daybreak, but will withhold mention in the forecast for now. Friday looks like a spectacular early autumn day with highs around 80, low humidity, and sunny skies.

The weekend forecast overall looks ok, though forecast confidence is a bit lower with some chance it could rain a bit at some point. Another trough is expected to pass well north of the area over the weekend with a weakening cold front reaching the area Saturday or Saturday night before probably washing out altogether. Cannot totally rule out a few showers with that front, but given weak frontal convergence, antecedent dry air mass, and minimal upper forcing, the more likely scenario looks to be dry weather for most. Southerly winds in advance of this front should allow temps to warm more solidly into the 80s on Saturday. Another trough is expected to move into the region early next week bringing what looks to be a somewhat better chance of showers and thunderstorms in the Monday/Tuesday time frame. There is still model variability in the timing and track of that trough, so forecast confidence is still on the lower end of the spectrum.

-Izzi / Borchardt

AVIATION /18Z TAFS THROUGH 00Z FRIDAY/

Issued at 1228 PM CDT Wed Sep 9 2026

Key Aviation Messages for the current TAF period:

- MVFR cigs linger through this afternoon. Moderate confidence on timing of improvement to VFR

Winds are currently out of the west around 10 knots. Most rain showers have dissipated for many terminals with linger showers south of a KVYS to KVPZ line. Most terminals remain under a broad area of MVFR cigs between 1000-1500 ft AGL, though isolated pockets of IFR cigs are occurring. There is lower confidence in IFR trends at any one terminal. However, as a front (observed on satellite imagery currently over southern Wisconsin) continues to move south over the region, VFR should return to all TAF sites by the late afternoon. Specific timing may be adjusted, but there is moderate confidence given latest satellite trends.

A drier period is in store for the TAFs beginning at 00Z tonight. VFR conditions are expected to prevail. As winds lighten this evening, they will turn to the northwest and eventually to the northeast around and after daybreak. There is the chance for a lake breeze to push inland tomorrow afternoon providing more easterly wind directions at Chicago terminals.

DK

LOT WATCHES/WARNINGS/ADVISORIES

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