textproduct: Chicago

KEY MESSAGES

- Isolated to widely scattered thunderstorms possible later this evening, though the threat of severe weather has decreased significantly.

- Dangerous swimming conditions at NW Indiana Lake Michigan beaches Sunday.

- Cooler temperatures early next week.

- Shower and thunderstorm chances return Tuesday and Wednesday. The possibility exists for another severe weather event on Wednesday.

DISCUSSION

Issued at 324 PM CDT Sat Jun 13 2026

Recently, a few isolated showers and storms developed across parts of LaSalle eastward into southern Kendall and Grundy counties, but have since decayed. Otherwise, we continue to monitor the threat for more substantial scattered showers and storms (some of which could be strong/severe) with a cold frontal passage this evening. Forecast guidance continues to support an uptick in scattered shower and thunderstorm development late this afternoon and evening in advance of this front. This appears plausible given that a mid-level impulse currently shifting eastward across IA will be overspreading the frontal zone as it moves into northern IL after 5 pm this evening. Additionally, low-level moisture return continues in advance of the front, and is noted by surface dewpoints already increasing into the upper 60s to near 70 in parts of northern IL.

Considering the environment in which these storms are, and will be, developing features deep-layer bulk shear in excess 35 kt, there remains a threat for some storms to become strong to severe into this evening. Accordingly, the SPC continues to have our area in a level 1 of 5 severe threat through this evening. While certainly not looking to be an outbreak of severe storms like the area experienced on Thursday, a few of the strongest storms could produce localized damaging wind gusts in excess of 60 mph and possibly a few instances of hail. The main threat of storms will end from northwest to southeast through the mid to late evening hours.

A few lingering scattered showers may linger in the wake of the cold frontal boundary for a period late tonight into early Sunday morning as the main mid-level impulse dives into the area. However, this activity is expected to quickly exit the region early Sunday, setting up a precipitation free day for the area. Temperatures will be much cooler for Sunday in the wake of this cold frontal passage, as breezy northwest winds (gusting up to 30 mph) usher in a cooler airmass. Accordingly, expect high temperatures generally in the low to mid 70s Sunday afternoon. The only real weather concern for Sunday is at Lake Michigan Beaches across northwestern Indiana, where the onshore breezy winds build waves up to 3 to 5 feet, setting the stage for a high swim risk. With this in mind, we have opted to hoist a Beach Hazard statement for our Lake IN and Porter county beaches on Sunday.

Another tranquil weather day is anticipated on Monday, though with a bit warmer temperatures. Thereafter, upper troughing, anchored by a Hudson bay area low, will support an enhanced belt of mid and upper-level northwesterly upper-level flow across the central CONUS through mid to late week. This should result in a return to a more active weather pattern again (return of showers and thunderstorms) for the middle of next week, which may drive another significant impulse into the lower Great Lakes region on Wednesday. Wednesday is thus another day to watch closely for our next potential notable severe weather threat.

KJB

AVIATION /00Z TAFS THROUGH 06Z MONDAY/

Issued at 640 PM CDT Sat Jun 13 2026

Aviation forecast concerns for the 00Z TAFs:

- Extent of any TSRA coverage expected to be lower than previous forecast thinking, and later this evening.

- Lingering scattered SHRA may persist from after midnight through around daybreak. Patchy MVFR vis/ceilings possible.

- Surface winds turn northwest behind a cold front late tonight, and become breezy Sunday with gusts 20-25 kt.

Early evening surface analysis depicts a cold front moving slowly east-southeast across central/southwest WI and far eastern IA. While airmass ahead of this front had destabilized to some degree (with a few convective SHRA/TS attempts since this afternoon), extensive cloud cover and remnant cold pool from earlier convective complex across the lower MO/OH Valley regions has suppressed destabilization and deeper moisture return to some extent. While isolated to widely scattered SHRA/TS can't completely be ruled out early this evening, it appears better forcing for higher convective coverage will be focused along/just ahead of the approaching cold front. In addition, a smaller footprint of convection appears likely, and thus have backed off a few hours of PROB30 mention after 01Z at RFD and 03Z for the Chicago terminals.

The cold front is expected to move through RFD around 04Z and ORD/MDW around 06Z, with a wind shift from WSW to NW. A mid- level disturbance lagging the front should produce a period of at least scattered showers behind the front overnight through around daybreak Sunday. Patchy MVFR vis/ceilings are possible in/near these showers. After daybreak and with increased diurnal mixing, northwest winds will become breezy with gusts 20-25 kt likely, with a BKN VFR stratocu deck lingering at least part of the day.

Ratzer

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...Beach Hazards Statement from Sunday morning through Sunday evening for INZ001-INZ002.

LM...None.