textproduct: Chicago

KEY MESSAGES

- Isolated to widely scattered showers and thunderstorms are possible (20-40% chance) this afternoon mainly near/south of I-80, but most areas will remain dry.

- Drier and more seasonable conditions are expected to start the week before stormier weather returns late week.

DISCUSSION

Issued at 152 PM CDT Sun Jul 5 2026

Early this afternoon, we're finding a cluster of light to moderate showers stirring over the lake. This cluster was brought on by a vort lobe spinning over the southern end of the lake about the back end of the departing trough. Notably weak convective layer shear isn't helping move these showers along very well as they track toward the south at near or less than 10 mph. Latest radar trends suggest that this activity should target portions of northwest Indiana within the next couple of hours. However, the southern extent of the showers has been fizzling away as of late and they may even fail to survive to the shore.

Coverage of isolated to widely scattered showers is anticipated to blossom and spread inland away from the lake as we progress through the afternoon, especially near and south of I-80. The greatest forcing tied to this vort will focus over the southern half of the CWA and a northeasterly low level wind field will continue to spread cooler, more stable low level air inland from the lake. Meanwhile, instability continues to build across outlying areas with several hundred to around 1,000 Joules of largely uncapped MLCAPE south of I- 80 and especially south of the Kankakee River expected for the mid-late afternoon. Latest CAM guidance generally favors areas near/south of the Kankakee River during the latter half of the afternoon and into early evening for the highest (still widely scattered) precip coverage. A handful of thunderstorms will be possible down in these parts as well. The limited instability and weak shear will inhibit a severe threat. However, the plentiful moisture, poor shear, and limited forcing beyond the low levels could make for slow-moving low-echo centroid pockets of heavy rainfall. Should a heavier shower or storm linger over an area that saw lots of rain or any flooding over the past few days, minor flooding impacts could be reinvigorated, although this is a low and isolated potential.

Farther north up into the Chicago metro and west of the lakeshore, the environment appears most supportive of precip as of this writing during the early part of the afternoon than later in the day. The footprint of the vort looks to spread inland carrying the better large scale forcing farther south for the mid-late afternoon. An isolated thunderstorm can't be ruled out north of I-80, but the odds are best prior to 3-4 PM. Additionally, a secondary vort ejecting east out of Iowa may help churn some additional shower activity farther west out toward I-39 where a handful of CAMs are resolving isolated pockets, mainly during the latter part of the day. Latest satellite trends show no distinct signs of new development anywhere around the area so it may end up being more of a late afternoon show, which adds confidence to there being little to no impacts north of I-80. Whatever precip coverage does materialize should wrap up by mid-evening as the trough axis moves across stripping forcing and moisture from the area.

Broad, relative high pressure behind the departing system will bring dry and mostly sunny conditions to Monday and Tuesday. Highs are forecast in the lower 80s for Monday and mid 80s on Tuesday. Onshore winds both days, however, will bring noticeably cooler conditions to locales near the lake with afternoon temps forecast in the lower and middle 70s around the lakeshore. The vort lobe from today will get hung up across central IL and central IN tomorrow and a handful of camps resolve pockets of daytime showers and thunderstorms similar to today but confined to our far southeastern CWA, if not outside of the CWA entirely. Couldn't argue with the NBM wanting to introduce some slight chances for storm or two down there tomorrow. Mid-summer heat will remain through the middle of the week with another synoptic system favored to traverse the region during the mid-late week period bringing additional opportunities for rain and thunderstorms.

Doom

AVIATION /00Z TAFS THROUGH 06Z TUESDAY/

Issued at 623 PM CDT Sun Jul 5 2026

Key Aviation Messages for the current TAF period:

- Showers and storms around and west of the Rockford Metro through sunset

- Lingering MVFR cigs for Chicago terminals with low confidence on exact timing for improvement to VFR

Lingering showers and storms along a confluence axis are persisting around KRFD. However, the lightning activity is already trending downward. Maintained VCSH for an hour, but drier conditions are slowly developing.

The main impact to the Chicago terminals are the low MVFR cigs. With little change to the overall weather pattern, it is understandable why a few models suggest MVFR cigs lingering into tomorrow morning providing lower confidence in improvement to VFR cigs. And yet, most models continue to suggest improvement and a gap in the cloud cover over Lake Michigan has developed and moving toward Chicago under the influence of the onshore flow. Outgoing TAFs will show improvement to VFR at 03z, but will reassess to see if MVFR needs to be extended further into the overnight.

Winds are expected to remain out of the northeast through the current TAF period. Speeds will diminish after sunset through the overnight before picking up again to around 10 knots tomorrow morning. Isolated gusts 15 to 20 knots are possible tomorrow morning, but not a signal for them to be frequent enough for mention in the TAF.

DK

LOT WATCHES/WARNINGS/ADVISORIES

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