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 /00Z TAFS THROUGH 06Z FRIDAY/

Issued at 529 PM CST Wed Nov 4 2026

Forecast concerns include...

Mvfr cigs through the period, with ifr cigs possible Thursday. Periods of drizzle and showers through the period. Wind shift/cold front to northerly Thursday afternoon/evening.

Areas of drizzle and a few showers will move across the terminals this evening with patchy drizzle likely to continue overnight and into Thursday morning. Though there remains uncertainty for how widespread the drizzle will be. Brief vis reductions will be possible with any of the drizzle that occurs. Scattered showers will be possible Thursday, especially along/ahead of a cold front that will move across the area in the late afternoon and early evening.

Prevailing mvfr cigs are expected through the period with areas of low mvfr cigs this evening, mainly with the drizzle. Low mvfr cigs are expected to become prevailing Thursday morning and and its possible ifr cigs may become prevailing by Thursday afternoon, especially across northwest IL and at RFD. The best chance of ifr cigs for the entire area appears to be with the cold front as it moves across the area. Cigs are expected to slowly lift back through mvfr Thursday evening, behind the cold front.

Southwest winds are expected through midday Thursday, gusting at times into the 20kt range. Winds will steadily turn northwest through mid afternoon Thursday, then shift northerly with the cold front. Its possible directions may remain around 360 degrees for several hours Thursday evening, as gusts increase in the 15-20kt range. cms

LOT WATCHES/WARNINGS/ADVISORIES

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