textproduct: Chicago

KEY MESSAGES

- After a relatively cool Wednesday, temperatures will trend upward Thursday onward.

- Several rounds of showers and storms are possible in the general region this weekend into early next week, some could be severe.

DISCUSSION

Issued at 317 AM CDT Wed May 13 2026

A much cooler airmass is moving overhead this morning on breezy northwest winds following yesterday evenings cold frontal passage. This unseasonably cool airmass in combination with a good amount of strato-cu cloud cover will result in high temperatures this afternoon only topping out in the low to mid 60s across inland portions of northern IL and northwest IN. Even cooler conditions are expected along the Lake Michigan lakeshore, where readings look to remain in the 50s this afternoon as winds veer off the lake.

The winds will remain breezy through the day, with gusts of 20-25 mph expected. Wind speeds are then slated to abate with sunset early this evening, then become light (<5 mph) overnight as a surface ridge of high pressure shifts overhead. Light winds under this high, in combination with clearing skies through the evening, will set the stage for another chilly night. Overnight temperatures are forecast to fall off into the upper 30s to low 40s inland from the lake and outside of Chicago. Some of the typically climatologically favored cool spots could even drop a bit lower (into the middle 30s), possibly resulting in some patchy frost development towards early Thursday morning. Fortunately, at this time, it appears the frost threat will remain limited, so we will forgo a formal mention in the forecast at this time.

Following a chilly start to the day on Thursday, increased sunshine and a moderating airmass through the day will help push inland temperatures back into the 60s to low 70s (warmest across interior sections of northern IL). However, continued onshore easterly winds across the northeastern IL Lake Michigan shore will keep conditions along and near the lake in the 50s to near 60. Dry weather is expected through the day. However, scattered rain shower chances will return to the forecast later Thursday night into Friday morning as the first of several mid- level impulses ejecting out of the southwest CONUS begins to move into the central CONUS.

While our area may experience a period of showers, and possibly some storms (especially in the south), Thursday night into Friday, the main focus for potentially more substantial showers and thunderstorms in our area will be this weekend into early next week. Deterministic and ensemble guidance remain in agreement that a potent surface low tracking eastward across southern Canada through late week will lay out a west-to-east oriented quasi-stationary surface frontal boundary somewhere across the Midwest into the lower Great Lakes region on Saturday. This front may become the focus for a few of waves of showers and thunderstorms this the weekend as the airmass south of the front moistens and destabilizes. Thereafter, a more pronounced upper trough digging into the western CONUS could drive a stronger storm system northeastward from the Plains through the Upper Midwest early next week. Such a system would support very warm and breezy conditions across our area early next week, along with continued chances of showers and thunderstorms, some potentially severe with heavy rainfall. Stay tuned!

KJB

AVIATION /12Z TAFS THROUGH 18Z THURSDAY/

Issued at 620 AM CDT Wed May 13 2026

NNW winds will occasionally gust 20 to 25 knots through at least early afternoon. A lake-enhanced NE wind shift with speeds up to 15 knots is then expected to cross the Chicago terminals sometime during the afternoon. Confidence in the exact timing remains low as the boundary may stall near the terminals for several hours this afternoon. It is quite possible that this occurs between ORD and MDW, which would lead to an early afternoon passage at MDW and late afternoon passage at ORD. By late evening, winds will settle NW under 5 knots or become calm/VRB as high pressure shifts over the area. Winds will then shift NE under 10 knots late Thursday morning as the high pressure exits to the east.

Areas of low-end VFR stratus will filter over the terminals this morning. While there may be a few instances of the stratus lowering to around 3kft/MVFR this morning, latest trends indicate chances continue to decrease. Otherwise, the VFR stratus will gradually lift this afternoon and dissipate tonight.

Kluber

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...None. LM...Small Craft Advisory until 7 PM CDT this evening for the IL nearshore waters.

Small Craft Advisory until 1 AM CDT Thursday for the IN nearshore waters.