textproduct: Chicago

KEY MESSAGES

- Today through Saturday will be beautiful with pleasant temperatures and relatively low humidity levels.

- Heat and humidity will return to the region Sunday and continue into Monday. The magnitude of heat may require heat headlines at some point.

- Multiple rounds of severe storms with destructive winds and flash flooding may occur in the Great Lakes region Sunday and Monday (but there are no guarantees that our area is impacted).

DISCUSSION

Issued at 237 AM CDT Thu Jul 23 2026

The center of a sprawling high pressure system will continue to meander southward through the region today offering a continuation of downright pleasant mid-July weather. Amidst little to no wind, temperatures today will rise into the mid to locally upper 70s. A lake breeze will push inland this afternoon though the limited marine/land airmass temperature difference will similarly limit the degree of cooling behind the boundary. A diurnal cumulus cloud deck will develop by mid-afteroon and fade this evening and humidity levels will remain quite comfortable (dew points in the upper 40s to lower 50s). All in all, today will be a "Chamber of Commerce" type day.

Tonight into tomorrow morning, a series of weak upper-level short- wavelength troughs will ripple through the middle Mississippi River Valley. Dry low-level air will limit the opportunity for any rainfall with either ripple in our area. With that said, an increase in mid- level clouds will hold low temperatures in the mid to upper 50s. Friday and Saturday look like gorgeous days as well with highs around 80, continued modest humidity levels, and south to southwesterly breezes.

Sunday onward, aggregate troughing will develop along the Pacific Coast enabling expansive upper-level ridging to expand across the northern United States. A quintessential summertime pattern is hence expected to set-up with an eastward-expanding dome of hot air. The heat will arrive to our local area on Sunday and continue into Monday with 850mb temperatures rising into the +21 to +23C range supporting highs in the lower 90s. Humidity levels will also be on the rise with evapotranspirationally-enhanced dew points rising into the mid 70s (if not higher). As a result, Sunday and Monday already have our attention for potential heat headlines across the area.

Sunday into Monday also continue to have our attention for a threat for severe weather and flash flooding in the broad region. Conceptually, the overlap of stout northwesterly flow and steep mid-level lapse rates on the eastern edge of the upper-level ridge atop moisture-laden instability across the Great Lakes will be supportive of quintessential summertime destructive wind-producing thunderstorm clusters. Ensemble guidance already exhibits fair consistency in showing a notable shortwave (originating from aggregate Pacific troughing to the west) shedding eastward and arriving in the Great Lakes on Monday, which may offer the peak coverage of severe weather in the region. Whether or not our local area is impacted by the upcoming MCS train or we just stay baking in the heat is something we'll assess as we get closer. Nevertheless, did touch base with SPC to collaborate on the introduction of severe weather probabilities in the broad Great Lakes region for Sunday and Monday.

Borchardt

AVIATION /06Z TAFS THROUGH 12Z FRIDAY/

Issued at 1226 AM CDT Thu Jul 23 2026

There are no key concerns for the 06Z TAF period.

Light winds will favor a SW direction through the night and into Thursday. A lake breeze will push inland and cross the Chicago sites likely during the early afternoon turning winds to ESE. Direction could get squirrel for a short period while the lake breeze is nearby, but sub-10 kt winds will be found on either side. Direction will return to SW during the evening while remaining light. Expect VFR throughout the period.

Doom

LOT WATCHES/WARNINGS/ADVISORIES

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