textproduct: Chicago

KEY MESSAGES

- Chances for showers and storms this afternoon around and south of I-80.

- Drier and warmer conditions are expected into early next with cooler conditions near Lake Michigan.

DISCUSSION

Issued at 221 AM CDT Fri Jul 10 2026

A cold front analyzed on mesoanalysis from northeastern Iowa to south-central Wisconsin is slowly sinking southward toward Illinois. However, remnants of a lake breeze has kept most of the surface winds in northern Illinois out of the northeast. There is a weak axis of moisture convergence from Monticello, IA to Michigan City, IN where spotty showers may continue to fester through daybreak. Lightning has only been intermittent, and forcing and instability is weak, suggesting that activity will continue to weaken through sunrise. The cold front will continue to slink southward through the morning helping to limit max temperatures today in the low to mid 80s, with mid to upper 70s closer to the lake.

Broadening the scale of current conditions, a look at national mosaic radar shows a large complex of showers and thunderstorms spanning from central Nebraska to central Kansas presently. Models are keying in on the chances that a mesoscale convective vortex (MCV) from this complex will transit eastward ahead of a 700 mb wave into central Illinois today. While coverage of showers and storms may wane in the morning, its arrival in central Illinois is expected to correspond to a diurnally favorable time of day with a largely uncapped environment and plenty of instability and decent low level lapse rates to redevelop showers and thunderstorms. Shear looks fairly meager, and models are trending the track of the MCV more to the southern part of the state. Better shower/storm coverage is expected farther south of the forecast area, but scattered activity could develop near US-24. Farther to the north, cannot completely rule out a slight chance (less than 25 percent) this afternoon of a few storms along a lake breeze and lingering moisture gradient in the vicinity of I-80.

An upper level ridge is expected to grow tomorrow over the central Plains and develop a southwest to northeast oriented axis from central Colorado to the Twin Cities on Sunday. That ridge is expected to continue to increase high pressure over the area and spread across much of the central CONUS. This should develop drier conditions, and as 850 mb temperatures increase to around 20C next week, there is a chance that temperatures in the low to mid 90s may return to the area. However, there is a little uncertainty with models not just in the strength of the high pressure/ridge, but also how a deep upper level low is expected to traverse across Canada next week. While warm and above normal temperatures are expected next week, it does not appear (at least at this distance) to compare to the previous heat wave that occurred at the start of the month. Not only is the temperature signature currently notably more muted, but with the high pressure projected to be situated over northern Illinois, there is a chance for daily lake breezes to set up and provide a little more relief, assuming the synoptic winds themselves are already out of the northeast. The warmest temperatures are currently projected around Tuesday or Wednesday, but that may change with updated guidance. Nevertheless, sunny and dry summer conditions are shaping up for next week.

DK

AVIATION /06Z TAFS THROUGH 12Z SATURDAY/

Issued at 1212 AM CDT Fri Jul 10 2026

The main aviation weather concerns are:

- Lingering showers and a few embedded thunderstorms in the central and southern parts of c90 tonight

- Developing IFR cigs and possible BR/FG overnight

An axis of showers, occasionally with a few embedded thunderstorms, continues to shift slowly southeastward. The general expectation is for storm coverage to diminish overnight, but at least isolated/spotty activity will probably fester through much of the overnight in the vicinity of an ARR- GYY line. Coverage and confidence remains too low for any TSRA mentions.

An area of IFR cigs continues to work its way slowly southwestward off the lake. Currently, this area of low stratus appears to be somewhat localized, but guidance suggests this will expand with time overnight. Continue with various TEMPO mentions for IFR overnight and into early Friday, with some potential future updates may need to prevail these conditions. In addition, some MVFR BR will be possible given the generally light low-level flow and moist airmass. Cigs should then gradually lift/scatter towards midday with VFR conditions expected through the rest of the TAF period.

Light/variable to northeasterly winds tonight will get a bit of a northeasterly boost with a lake breeze Friday afternoon.

Carlaw

LOT WATCHES/WARNINGS/ADVISORIES

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