textproduct: Chicago

KEY MESSAGES

- The next few days will be offer seasonably cool temperatures, comfortable humidity values, and no threat of rain.

- Conditions will remain hazardous at all Southern Lake Michigan beaches through Thursday morning.

- Heat, humidity, and chances for storms will return early next week.

DISCUSSION

Issued at 142 AM CDT Wed Jul 22 2026

It sure looks and feels more like fall than the middle of July early this morning with deep upper-level cyclonic flow anchored by seasonably cool temperatures and pockets of lake-induced stratocumulus clouds! The change in regime is exemplified by a drop in 800mb temperatures of about 12C/24 hours per the last two 00Z RAOBs at GRB, a range from roughly the 90th to 10th percentiles. The stage is thus set for a beautiful stretch of days with seasonably cool temperatures, low humidity values, and no threat for rain. Highs today will top off in the low to mid 70s and increase by a few degrees each day through the end of the week. Overnight lows will be comfortable and start in the lower 50s tonight rising to the lower 60s by Friday night. The only fly in the ointment in an otherwise pleasant period is hazardous waves along all southern Lake Michigan beaches today through Thursday morning.

The reprieve from the heat will be short-lived as upper-level ridging redevelops across the central United States this weekend. Highs will climb back into the upper 80s to lower 90s as early as Sunday and continue through next week. Humidity levels are also poised to rise with agricultural evapotranspiration likely augmenting near-surface dew points into the mid 70s. The next opportunity for storms will arrive in the Sunday/Monday (July 26/27) timeframe along the precarious northeastern side of the building upper-level ridge. The EPS in particular is bullish with 51-member mean MUCAPE already exceeding 2000 J/kg and over 50% of members with a PWAT exceeding 2 inches. This will be a period to watch for severe weather in the general Upper Mississippi River Valley/Great Lakes region.

Borchardt

AVIATION /12Z TAFS THROUGH 18Z THURSDAY/

Issued at 606 AM CDT Wed Jul 22 2026

Key messages for the 12Z TAF period:

* NNW winds will gradually kick over to NNE by around 15Z at the Chicago sites.

Starting the day off with NNW to N winds (340-360) near or below 10 kt. Direction will continue to favor NNW early this morning and slowly veer to NNE. 15Z is best guess on wind shift timing at ORD and MDW, but could see a couple hour period of pure N. Winds will then go light and variable for the overnight and go light westerly for the start of Thursday. A shift to easterly will occur sometime Thursday morning or afternoon, although timing is very unclear and winds should remain light on either side of the shift. Expect VFR throughout the period.

Doom

LOT WATCHES/WARNINGS/ADVISORIES

IL...Beach Hazards Statement through this evening for ILZ006-ILZ103- ILZ104.

IN...Beach Hazards Statement through Thursday morning for INZ001- INZ002.

LM...Small Craft Advisory until 10 PM CDT this evening for the IL nearshore waters.

Small Craft Advisory until 4 AM CDT Thursday for the IN nearshore waters.