textproduct: Chicago

KEY MESSAGES

- Times of rain continue through Friday, greatest chances occur later Thursday into Thursday night. Some drizzle could occur tonight.

- Occasionally breezy and cool conditions are expected through Friday.

- Freezing temperatures will be possible Friday and Saturday nights and Sunday night could have a small portion in far northwest IL.

DISCUSSION

Issued at 1140 AM CST Wed Nov 4 2026

A cutoff low pressure system continues lumbering northeastawrd and interacts with another vigorous southward-moving area of vorticity from central Canada today through Friday. As a cold front and associated dry slot swings through this afternoon, 850 mb temperatures drop from the low teens to the single digits below zero Friday and Friday night indicating cooler air entering the region. Temperatures fall back into the 30s Thursday night with lower 40s in NW IN where extra lake effect clouds will be possible. Then, lows fall back into the upper 20s to mid 30s across NW IL Friday night and similar temperatures will also be possible Saturday night. Additionally, gusts between 20 and 30 mph decrease this evening, but a few sporadic 20 to 25 mph gusts cannot be ruled out overnight. Gusts between 20 and 25 mph could still occur on Thursday as a trough drops down within the north and western side of the low. Some wrap around spotty showers and drizzle are likely along and out in front of this disturbance. This large area of resultant vorticity now slides southeastawrd as a surface high slides through overhead into the south central CONUS. Then, as the disturbance and cold air move Lk MI, lake effect showers will be possible over NW IN and over Lk MI. High pressure follows behind and switches trajectories around decreasing instability, and dry air comes in. This allows high temperatures to warm back up through the weekend in the 50s to the 60s for next week. Lows warm through the 30s around the middle of next week.

Northwest flow aloft takes over into next week as ridging ins entrenched across the southwestern CONUS. This keepss the forecast area dry through the rest of the forecast period as energetic waves stay to the north near the border with Canada.

Roller

AVIATION /12Z TAFS THROUGH 18Z THURSDAY/

Issued at 604 AM CST Wed Nov 4 2026

Main Concerns:

- Lower CIGs most of the period

- Showers and/or drizzle at times

- breezy conditions around 20 kts

MVFR conditions (primarily CIGs) are expected to continue as an upper low moves overhead and dampens out. Some patchy drizzle or a few areas of light rain are possible overnight into early Thursday within the dry slot. Some wind gusts around 20 kts will be possible at the TAF sites primarily this afternoon and Thursday morning, but a few cannot be ruled out overnight as well. Wind will continue to be out of the southwest through the period.

Roller

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...None. LM...Small Craft Advisory until 3 PM CST Thursday for the IL and IN nearshore waters.