textproduct: Chicago

KEY MESSAGES

- A cold front will move across the area today accompanied by isolated to scattered showers (20-30% chance at any given spot). A lightning strike cannot be ruled out (~10% chance).

- Periods of showers and a few storms are expected Friday night through early Saturday afternoon (>60% chance areawide). Coverage of showers may taper in time for outdoor Halloween activities.

- Generally mild conditions will continue into the first week of November, through a changing weather pattern will result in potentially several periods of wet weather through the week.

DISCUSSION

Issued at 208 AM CDT Thu Oct 29 2026

It is an unseasonably mild early morning across the region, with temperatures holding in the low to mid 60s (warmest in Chicago) in most locations. However, a cold front is quickly approaching from eastern Iowa. Widely scattered showers and a few embedded thunderstorms are ongoing ahead of the front within a corridor of enhanced warm air advection. This activity will push eastward into northern Illinois through the predawn hours, though coverage should diminish as it encounters some drier air over northeastern Illinois. Consequently, showers in the Chicago metro area around daybreak are expected to remain hit or miss.

Abnormally high dewpoints (mid to upper 50s) and modestly steep mid-level lapse rates ahead of the front may trigger renewed shower development by midday or early afternoon as the boundary shifts southward across the I-88 and I-80 corridors. Shower coverage will likely remain low due to weak large-scale forcing and modest instability, but isolated to scattered activity is expected to move east-southeast along the front this afternoon.

While there is no strong push of cold air behind the front, temperatures will turn cooler from north to south late this afternoon and evening, dropping into the 50s by sunset. A surface high building into the western Great Lakes will bring a chilly, more seasonable night with efficient radiational cooling. Lows are forecast in the upper 30s to low 40s away from the Chicago urban heat island.

More seasonable weather is expected into the weekend, particularly Friday and Saturday, as onshore easterly flow, extensive cloud cover, and occasional rain persist. Highs will generally reach the 60s, though areas north of I-80 in northern Illinois may struggle to climb out of the 50s.

Attention then turns to a conglomerated upper-level wave expected to track from Mexico east-northeastward into the Lower Great Lakes region during the weekend. There continues to be a strong signal amongst model and ensemble guidance for a period of warm air advection (isentropic upglide) driven showers across our area, particularly Friday night through at least Saturday morning. We also continue to see a signal for gradually waning shower coverage late in the afternoon hours (hopefully in time for outdoor Halloween activities). Temperatures will be cooling back through the 50s after sunset.

The area looks to largely get a break in the coverage and chances of rain Saturday night and Sunday. However, there continues to be a strong ensemble signal for a large upper trough to set up over the Plains into the Midwest next week. This looks to support potentially several periods of wet weather across our area through much of the first work week of November.

KJB

AVIATION /12Z TAFS THROUGH 18Z FRIDAY/

Issued at 634 AM CDT Thu Oct 29 2026

Key messages for the 12Z TAF period:

* Isolated showers into Chicagoland early this morning

* A potential period of MVFR cigs late morning into afternoon

Isolated light showers will be found around Chicagoland through around 13Z. A period of MVFR cigs will then be possible during the late morning into the afternoon. Confidence is shaky in cig trends today and the window of MVFR may be brief while some guidance suggests it could linger into late afternoon. An additional isolated shower can't be ruled out in the late morning to early afternoon window, as well.

SSW winds near or just over 10 kt may occasionally gust to near 20 kt while they veer through the morning going NW by early afternoon. Expect light NNW during the evening flipping to NE overnight at RFD and DPA and not until Friday morning at ORD, MDW, and GYY.

Doom

LOT WATCHES/WARNINGS/ADVISORIES

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