textproduct: Chicago

KEY MESSAGES

- The week looks fairly pleasant with the only threat for rain being Tuesday night through Wednesday.

DISCUSSION

Issued at 1216 PM CDT Mon Sep 7 2026

Mostly sunny skies, relatively low humidity values, and seasonably warm temperatures in the upper 70s to lower 80s are making for a beautiful Labor Day in the Great Lakes thanks to a large high pressure system centered over southern Ontario. Tonight looks similarly pleasant with overnight lows around 60, low humidity values, and light winds. Suppose a few patches of ground fog cannot be ruled out toward day break near river valleys and farm fields, but will withhold mention in the forecast for now.

Tomorrow, the semi-persistent upper-level ridge over the central United States will begin to flatten as an upper-level trough and associated surface low lift into central lower Canada. An increase in south to southwesterly winds will advect a warmer airmass into the region with highs poised to rise into the mid to upper 80s. A lake breeze should develop by early afternoon and stall inland with cooler temperatures along the lakeshore.

Tomorrow afternoon and evening, showers and thunderstorms will develop in a low-level confluence axis across Iowa and Wisconsin. With time, the activity will tend to outrun any upper-level ascent leading to a gradual weakening trend while approaching and especially crossing the Mississippi River. Can nevertheless still envision scattered showers and perhaps a storm moving across the area overnight through Wednesday morning, but will cap PoPs at 60% to signal a lower coverage/QPF event.

After morning showers, Wednesday afternoon is looking relatively quiet. Highs will depend on how fast clouds clear and should range from the low to mid 80s. A few showers and storms may attempt to develop across the south and east portions of our forecast area depending on where any residual front stalls.

Thursday and Friday look pleasant as a surface high pressure system work into the Great Lakes region. Opted to cut NBM temperatures by several degrees each day to feature highs generally in the mid to upper 70s both days. Ensemble guidance then suggests warming temperatures by the weekend accompanied by the next opportunity for rain.

Borchardt

AVIATION /18Z TAFS THROUGH 00Z WEDNESDAY/

Issued at 1216 PM CDT Mon Sep 7 2026

No major forecast concerns at the terminals for this TAF period as high pressure will remain in control. Winds this afternoon will continue to be a bit on the breezy side with speeds around 10-12 kts out of the east-southeast but will ease around sunset. Directions will veer overnight before settling into a south- southwest (180-190) orientation Tuesday morning with speeds increasing once again into the 8-10 kt range. Otherwise, expect mostly sunny skies today to give way to gradually increasing VFR cirrus late tonight through Tuesday.

Yack

LOT WATCHES/WARNINGS/ADVISORIES

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