textproduct: Chicago

KEY MESSAGES

- Dry but cooler conditions Wednesday and Thursday, followed by increasing rain chances Friday.

- Intermittent shower/thunderstorm chances for Memorial Day weekend, though much of the period should be dry.

- Several periods of moderate to high swim risk conditions possible through early next week due to persistent northeast winds over Lake Michigan.

DISCUSSION

Issued at 237 PM CDT Tue May 19 2026

A cold front currently nearing the I-39 corridor across the western CWA will shift eastward across the forecast area through the remainder of the afternoon. With the combination of an outflow boundary early this morning now east of I-57, increasing low-level cloud cover, and 600-800 hPa warming, the potential for any storms or appreciable heavier showers appears to be confined to the extreme southeast CWA (south of a Paxton to Rensselaer line) for the next few hours. Otherwise, spotty shallow showers remain possible anywhere ahead of the cold front through the daytime hours.

Though the front will track well south and east of the area tonight, modest low-level frontogenesis in response to a broad mid to upper- level jet may yield either a few light showers or a band of light rain across the far southern CWA overnight into mid-morning Wednesday.

High pressure will expand across the northern Great Lakes Wednesday through Thursday. Expect dry but cooler conditions amid persistent northeast winds through this period.

A Pacific wave off the Baja of California will bring an area of increased mid-level moisture across the central CONUS late this week as low-level Gulf moisture is drawn northward toward the mid- Mississippi River Valley. Though stout low-level drying from the northeast over the Great Lakes will impede the initial northward extent of rain on Friday, the overall translation of deep moisture northward should overcome the low-level dry air and bring an area of rain across most of the area by late Friday. Poor mid-level lapse rates will greatly limit thunderstorm chances.

A gradual warmup appears in store this weekend into early next week as broad ridging builds over the north-central CONUS. However, there remains substantial model disagreement as to whether a larger southwest CONUS trough late this week becomes cut-off over the southern Plains/Texas or remains loosely tied to the western edge of the ridge. The latter solution would bring cooler and more unsettled weather to the area late in the weekend and delay any potential warm- up to next week.

As an added note, we are nearing the start of the Beach Hazards season. Given the potential for multiple periods of northeast winds and higher waves this week/weekend into next week, swim risk messaging may need to increase in the next couple days.

Kluber

AVIATION /18Z TAFS THROUGH 00Z THURSDAY/

Issued at 102 PM CDT Tue May 19 2026

Key Messages:

- Breezy west-southwesterly to westerly winds to continue through this afternoon.

- MVFR ceilings may be observed at times through tomorrow morning.

Breezy west-southwesterly winds with peak gusts in the 25-30 kt range will continue through the early afternoon before turning more westerly as a cold front tracks across the area over the next few hours. Winds will then turn northerly overnight before becoming northeasterly after sunrise tomorrow.

MVFR ceilings should become more commonplace after the cold front moves through and will likely hang around the area in some capacity through tomorrow morning, but VFR conditions are still favored to prevail through a good chunk, if not most, of this time frame. Additionally, still couldn't rule out a few isolated showers or sprinkles passing near the terminals this afternoon as the cold front passes by, but dry conditions are otherwise favored to prevail through the TAF period.

Ogorek

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...None. LM...Small Craft Advisory until 4 PM CDT this afternoon for the IL and IN nearshore waters.