textproduct: Chicago

KEY MESSAGES

- Seasonably warm today for Labor Day with mostly sunny skies and no rain in the forecast.

- Rain and thunderstorm chances return to the forecast Tuesday night and Wednesday.

DISCUSSION

Issued at 256 AM CDT Mon Sep 7 2026

Our Labor Day is off to a quiet start. Temperatures are slowly falling through the 60s and blowoff cirrus is scooting overhead from decaying convection to the west. There is a signal for some patches of fog to develop south of I-80 as well as west of the Fox River valley toward daybreak which seems reasonable since dewpoint depressions are nearing zero across a number of sites early this morning in these areas. Accordingly, added some patchy fog to the morning forecast over these areas. Otherwise, weather looks seasonably pleasant for the holiday today with highs in the lower 80s away from the lake and middle to upper 70s closer to the lakeshore, coolest near the Illinois lakeshore. Also looking at plenty of sunshine filtered by passing high level clouds and a bit of an E breeze.

The ridge axis will pass over tonight turning the wind field to southerly which will promote a bit of a warmup for Tuesday with highs forecast in the middle 80s to near 90, including up to the lake with the offshore flow.

Immediately in the wake of the ridge, a deepening upper low will track west to east across southern Canada during the middle part of the week and drag a surface cold front across the area on Wednesday bringing our next opportunity for rain and thunderstorms. Models have come into much better alignment regarding this system over the past 24 hours. The main window for precip looks to be from late Tuesday night into Wednesday afternoon as the front moves into our northwest, during what is not typically a diurnally favorable window for thunderstorm development. Overall, convective parameter spacing during this time is marginal with modest, largely capped instability ahead of the front and the much better forcing and shear staying wrapped up in the circulation to our north. Efficient warm advection and moist upglide ahead of the front may help convection get going, particularly through the morning hours. General expectation is a southeastward-moving line of scattered to widespread showers with some embedded thunder coverage, highest favored during the earlier half of the day Wednesday. The marginal severe potential we'd been eyeing is beginning to look like a bit of a stretch. The better dynamic and kinematic environments will lag well behind the surface front into Wednesday and won't catch up until Wednesday night or early Thursday as the upper trough axis encroaches. By this time, the front should be parked across central IL and rain chances Wednesday night into Thursday should be confined to our far south, if not out of our CWA altogether. SPC's new Day 3 features a marginal risk across central IL abutting our southern CWA for later Wednesday night.

High pressure will then overspread the region late in the week beneath the windward side of the departing trough. Seasonably warm conditions will continue through the end of the week. A number of subtle disturbances tracking overhead may drive periodic chances for rain over the weekend. Medium range guidance continues to favor a larger synoptic system bringing rain to the region in the late Sunday to Monday period.

Doom

AVIATION /12Z TAFS THROUGH 18Z TUESDAY/

Issued at 613 AM CDT Mon Sep 7 2026

VFR conditions with light east to southeasterly winds expected through early Tuesday morning. Winds will likely become more southerly by mid-late morning Tuesday, but remaining less than 10kt.

- Izzi

LOT WATCHES/WARNINGS/ADVISORIES

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