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 /12Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 546 AM CST Tue Nov 10 2026

There are no significant aviation forecast concerns for the current TAF period at this time, but there are a handful of "nuisance" items of note with the current set of TAFs.

First, generally northwesterly winds under 10 kts are expected today, though a weak lake breeze will likely result in northeasterly winds prevailing at GYY this afternoon. Depending on where this boundary sharpens over Cook County, winds may also turn easterly at MDW and ORD at some point this afternoon or around sunset, but confidence in this occurring is only low- medium. Either way, flow on either side of the boundary should be light (at or around 5 kts).

Some model guidance is hinting at a potential for areas of fog to develop overnight tonight and affect some of our TAF sites. However, confidence in this occurring is low given that upper- level cloud coverage and opacity will be steadily increasing tonight and that high-resolution model guidance has been too aggressive with fog development the past few nights.

Lastly, an incoming upper-level disturbance and associated low pressure system will arrive in northern Illinois tomorrow morning, bringing a chance for rain showers. With a notable amount of dry sub-cloud air to work through, the better chances for any showers to affect the terminals should come during the afternoon tomorrow, though a few sprinkles could nevertheless start to be observed towards the very end of the current 30-hour TAF window for ORD and MDW.

Ogorek

LOT WATCHES/WARNINGS/ADVISORIES

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