textproduct: Chicago

KEY MESSAGES

- Above to much above average temperatures expected to continue through the upcoming weekend.

- While not a wash out, there will be some periodic chances for showers and perhaps isolated thunderstorms at times late Wednesday night through the upcoming weekend.

DISCUSSION

Issued at 155 AM CDT Tue Oct 27 2026

The cold front that shifted across our area yesterday morning has stalled across central Illinois and Indiana. Light winds and low dew point depressions near the front may support a brief period of early morning fog, primarily across the southern counties. We will continue to monitor this overnight, but widespread dense fog appears unlikely.

During the day today, this front will lift back northward as a warm front as a shortwave impulse over Kansas and Oklahoma tracks northeastward across the Mid and Upper Mississippi Valley. This impulse will bring extensive mid- and upper-level cloud cover through the day, but a drier low-level airmass should keep conditions rain-free. Despite the cloud cover, warm air advection will push temperatures inland into the upper 60s to low 70s this afternoon. Closer to the lake, southeasterly winds ahead of the approaching front will favor an afternoon lake breeze into northeastern Illinois, slowing the warm front's progress and keeping temperatures several degrees cooler than inland areas.

After the warm front shifts north of the area tonight, Wednesday is shaping up to be unseasonably mild area-wide. High temperatures are forecast in the low to mid-70s Wednesday afternoon.

The next notable shortwave impulse is expected to track well north across southern Canada Wednesday night. As an associated surface low moves eastward across Ontario, a southwestward- trailing cold front will push southward into our area by Thursday. Although the strongest large-scale forcing will pass well to the north, pooling low-level moisture (dew points in the mid to upper 50s) along the frontal boundary could support isolated to widely scattered showers, particularly late Wednesday night into Thursday. Consequently, we maintain low- end (2030%) chances of precipitation during this period.

Temperatures will turn slightly cooler for the end of the week behind this front. However, with no strong cold airmass behind Thursday's front, temperatures should remain above average through the weekend. Periodic rain chances (and possibly a few thunderstorms) will increase late in the weekend and into next week. Ensemble guidance suggests a series of impulses will track from Mexico east-northeastward into the Lower Great Lakes region during the weekend, followed by a potentially more substantial system tracking slowly across the central U.S. next week. As a result, there will be daily chances for rain from Saturday into next week. Dry periods are still expected, so it will not be raining continuously throughout the weekend.

KJB

AVIATION /12Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 640 AM CDT Tue Oct 27 2026

Key messages for the 12Z TAF period

* Low potential for a brief window of MVFR cigs after sunrise today

Light easterly winds will become SE to SSE at near or below 10 kt today. It's possible that direction goes southerly for a period this afternoon before backing again late afternoon. Light southerly winds overnight will favor SSW, and Wendesday will begin at SSW.

A persistent signal exists for a period of MVFR cigs over the Chicago sites and GYY this morning after daybreak. This is a seemingly low potential, at least too low to include in this TAF package. Should low cigs materialize this morning, they should scatter out by mid- morning. Otherwise, VFR throughout the period.

Doom

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...None. LM...Small Craft Advisory until 10 AM CDT this morning for Winthrop Harbor to Wilmette Harbor IL.