textproduct: Chicago

KEY MESSAGES

- Showers and a few storms will move across the area late tonight through Wednesday.

- Thursday and Friday look pleasant.

- The next opportunities for rain will arrive this weekend and continue into early next week.

DISCUSSION

Issued at 120 PM CDT Tue Sep 8 2026

Per a recent subjective surface analyses, a 1000 mb surface low pressure system is moving across southern Manitoba well to the north of a surface high pressure system parked along the Atlantic coast. A cold front extends southward from the low pressure system through northern Minnesota and across the central Plains. Ahead of the front, a broad ribbon of somewhat unfocused low-level isentropic ascent is supporting areas of showers and thunderstorms from Nebraska northeastward into central Wisconsin. A pocket of relative dry air is present southeast of the axis of isentropic ascent, which is leading to a pleasant day across the Lower Great Lakes.

This afternoon and evening, the upper-level wave currently supporting showers and thunderstorms across eastern Nebraska will shift eastward into Iowa and support the expansion/invigoration of thunderstorms. After sunset, radar data to our west may look rather intimidating with what may be several clusters of strong to severe storms moving toward the Mississippi River. Thankfully, the environment east of the river will be hostile for thunderstorms to maintain their intensity, so the expectation remains for thunderstorm clusters to gradually weaken as they traverse eastward into northern Illinois through the night. Peak coverage of activity through daybreak should be mainly along and north of I-88 and west of I-39.

With time, the axis of remnant showers will drift southward through the area from sunrise through early afternoon on Wednesday. Coverage should then decrease with time from north to south through the afternoon as a cold front works across the area. Redevelopment of thunderstorms along the front appears to be a largely unfavored scenario given limited opportunities for destabilization tomorrow. In all, the next 24 hours doesn't look like a complete washout across our area with most areas favored to get less than 0.5" of an inch of total rainfall.

Temperatures tomorrow will be modulated by remnant showers and cloud cover. While there are some prospects for clearing from north to south through the afternoon, did opt to cut back NBM temperatures to largely advertise highs around 80 degrees. Tomorrow night, a few waves propagating along the front should allow for additional waves of showers and a few storms primarily south of our area. Did cut back on NBM PoPs to paint low-end chances (20-40%) for showers near the US-24 corridor through daybreak Thursday.

A surface high pressure system will slide through the region Thursday and Friday leading to quiescent conditions. Both days will be characterized by mostly sunny skies, light winds, and highs around 80 degrees. A series of upper-level waves may provide the opportunity for a few windows for precipitation this weekend into early next week.

Borchardt

AVIATION /06Z TAFS THROUGH 12Z THURSDAY/

Issued at 1229 AM CDT Wed Sep 9 2026

Key messages for the 06Z TAF period:

* Showers with a few embedded thunderstorms overnight through Wednesday morning

* MVFR possible after daybreak with the rain and perhaps lingering into this afternoon

A line of showers with a few embedded thunderstorms is working across northern Illinois. Rain is ongoing at RFD and should reach the Chicago sites by around 08Z. Near and after daybreak, periods of heavier rainfall with associated MVFR will be possible. Rain will move away near the end of the morning. Thunder coverage looks to remain isolated. MVFR cigs are favored to persist into the mid to late afternoon.

Light to calm winds overnight will go westerly for Wednesday at near or below 10 kt and veer to NNW late Wednesday night.

Doom

LOT WATCHES/WARNINGS/ADVISORIES

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