textproduct: Chicago

KEY MESSAGES

- Dry conditions and warmer temperatures continue through Tuesday.

- Precipitation chances and cooler temperatures return mid to late week, including periods of lake effect showers.

DISCUSSION

Issued at 251 PM CST Mon Nov 9 2026

A weak cold front moving through tonight will shift winds to the northwest on Tuesday. Despite the frontal passage, minimal low- level air mass contrast will keep temperatures mild, with highs similar to today, ranging from around 60 degrees north of I-80 to the low-to-mid 60s to the south.

A broader pattern shift will unfold across North America during the mid-to-late week period. Upper-level ridging over western North America will carve out a trough across the eastern U.S. Thursday into Friday, bringing cooler and more unsettled weather to our region. However, ensemble guidance suggests the upper ridge will expand eastward into the central and eastern U.S. by early next week as a deep trough develops over the eastern Pacific into western North America. Consequently, after a couple of days of colder weather with scattered showers, temperatures are expected to moderate back above normal early next week.

The amplifying upper-level pattern will drive a compact shortwave east- southwestward across the Mid-Mississippi Valley on Wednesday. Model and ensemble guidance continue to target a surface low track somewhere over central Illinois into Indiana Wednesday afternoon and evening. This keeps the highest rain chances (60%+) primarily south of I-80. A few thunderstorms cannot be ruled out late Wednesday as lapse rates steepen ahead of the low, but these chances also remain focused south of I-80 into central Illinois and Indiana.

In the wake of Wednesday's system, several additional shortwave impulses diving into the Upper Midwest and western Great Lakes will merge into a broader trough across the eastern half of the country Thursday into Friday. A colder airmass will shift over the area for the end of the week accompanied by gusty northerly winds. While shower chances will persist on Thursday for most areas, lake-induced thermodynamics will foster a transition toward primarily lake- effect precipitation late Thursday into Friday. Uncertainty remains regarding the low-level flow orientation (NNE vs. NNW/NW), which will determine how far west lake-effect showers drift into northeast Illinois versus remaining focused over northwest Indiana. Precipitation type also remains uncertain Thursday night into Friday morning, when temperatures may become cold enough to support a period of wet snow, particularly just inland from the lake in northwest Indiana.

A strong surface high expanding eastward over the weekend into early next week will bring an end to lake-effect showers, leading to another stretch of dry weather with temperatures gradually moderating back into the 50s.

KJB

AVIATION /00Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 506 PM CST Mon Nov 9 2026

There are no significant aviation weather concerns. A weak cold front will result in a northwest wind shift overnight. A weak lake breeze will develop Tuesday afternoon. Currently, chances for this making it to MDW appear too low for a mention in the TAFs, but will include a NE shift at GYY.

Carlaw

LOT WATCHES/WARNINGS/ADVISORIES

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