textproduct: Chicago

KEY MESSAGES

- Slightly warmer today with highs in the low to mid 60s, then turning cooler through the end of the week.

- Shower chances return Wednesday (30 to 50%) with isolated thunderstorms possible well south of I-80 in the afternoon (20% chance).

- Periods of lake effect rain showers are expected Wednesday night through early Saturday morning, particularly in northwest Indiana. Snow is likely to mix in at times.

DISCUSSION

Issued at 328 AM CST Tue Nov 10 2026

Another pleasant fall day is in store today with light winds and slightly warmer temperatures in the low to mid 60s. Northwest winds will keep temperatures cooler near the lakeshore in Indiana, in the mid to upper 50s. Only item of note for tonight is a low chance for fog development near and south of I-80. Have held off on a formal mention in the official forecast for now due to the potential for high clouds to move in earlier and also noting that hi-res guidance has been over- forecasting fog development the past few days.

Heading into Wednesday, a compact shortwave and associated surface low are expected to track across the region. There remains some uncertainty in the coverage of showers owing to residual low-level dry air, which may keep things more isolated to scattered initially. Have accordingly maintained mainly 30 to 50 percent chances for showers with this update. Steepening mid-level lapse rates may provide just enough instability for increasing shower coverage in the afternoon along with the potential for lightning strikes, mainly south of a Pontiac to Rensselaer line (20% chance).

The departing wave eventually phases with an amplifying upper trough across the eastern CONUS Wednesday night, which will allow a much cooler airmass to descend into the region through the end of the week. While embedded mid-level vort lobes rounding the resultant closed upper low may bring a few showers farther inland through the day on Thursday, focus continues to be on the persistent signal for a robust band of lake effect showers to set up over Lake Michigan, potentially through early Saturday morning. This continues to seem reasonable at this distance given favorable lake-induced thermodynamics and northerly fetch. While occasional westward wobbles in the position of the band may occur, trends have been toward the band focusing mainly into northwest Indiana Thursday night through Friday.

The primary precipitation type is expected to by rain with these showers, though snow is likely to mix in at times. There has been ensemble support for slushy accumulations into portions of northwest Indiana. However, warm lake temperatures (mid 50s), marginal convective cloud-top temperatures (~11C), combined with warm antecedent ground temperatures may limit this potential overall. With all of this said, we will continue to monitor trends closely. Winds will also be strong near the lakeshore in Indiana with gusts up to 35-40 mph at times during this period.

In addition to cooler daytime temperatures, inland areas away from the lake effect clouds may see temperatures fall near to below freezing each night through the end of the week. Long- range ensemble guidance indicates the colder pattern will be fairly short-lived as upper ridging builds back into the region early next week, bringing a return to above normal temperatures for mid-November.

Petr

AVIATION /06Z TAFS THROUGH 12Z WEDNESDAY/

Issued at 1106 PM CST Mon Nov 9 2026

There are no significant aviation weather concerns. Southwesterly winds will become northwesterly tonight behind a weak cold front. A weak lake breeze will develop Tuesday afternoon and may get close to MDW, but chances of a meaningful wind shift remain too low for a mention in the TAF. A brief northeast wind shift appears more likely at GYY.

Winds will then become light and variable at times Tuesday night. Any threat for precipitation looks to hold off until just beyond the extended ORD/MDW TAF window.

Carlaw

LOT WATCHES/WARNINGS/ADVISORIES

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