textproduct: Chicago

KEY MESSAGES

- Spring-like temperatures through the weekend, though Lake Michigan will moderate temperatures along the shoreline.

- Cooler temperatures are expected early next week after a cold front passes on Sunday.

DISCUSSION

Issued at 207 AM CDT Fri Mar 20 2026

An anomalously strong upper-level ridge over the southwest CONUS will gradually deamplify while shifting across the central CONUS through the weekend. During this time, a pair of sheared waves originating from the Pacific Northwest will cross the Great Lakes region.

A shallow lake-enhanced cold front that crossed northern Illinois Thursday afternoon/evening has since washed out over or just south of the CWA early this morning. Developing low-level southwest flow and some diurnal heating ahead of the first wave will quickly mix out the front across at least the south half of the CWA, possibly to the I-88 corridor, through early afternoon. Another cold front associated with the first wave will then shift SSW across northern Illinois through the afternoon. Highs across the Chicago metro, especially near the lake, will hinge significantly on the timing of the frontal passage. Expectations are that highs will range from near 60 along the Wisconsin state line to the mid 70s toward central Illinois, with temps quickly falling into the 40s near the lake and 50s inland mid to late afternoon.

The front will retreat/wash-out amid developing breezy southwest winds on Saturday ahead of the second wave to the north. While some morning stratus may linger across northern Illinois in the morning, modest WAA will push temps back into the mid 60s north to mid 70s south.

The cold front tied to the second wave is expected to cross the area from north to south Sunday morning into early afternoon. A relatively dry airmass ahead of the front as well as strong low and mid-level capping suggests a dry frontal passage. A band of anafrontal precip with perhaps an embedded elevated thunderstorm is possible late Saturday morning through the afternoon amid temps falling into the 40s.

Broader WNW flow across the northern CONUS will take hold across much of next week, with a continued series of waves crossing somewhere across the Great Lakes region. Cooler but seasonable conditions will prevail as high pressure passes north of the area Monday and Tuesday. However, a compact wave removed from the stronger WNW flow aloft is progged to pass just southwest of the area on Tuesday and may brush the area with a few showers. Dry conditions and warming temperatures are favored Wednesday and Thursday ahead of a stronger trough passing north of the area.

Kluber

AVIATION /12Z TAFS THROUGH 18Z SATURDAY/

Issued at 614 AM CDT Fri Mar 20 2026

A cold front will move across the terminals late this morning/ early this afternoon resulting in a wind shift to northwest. Lake breeze is expected to develop this afternoon and flip winds to northeast at GYY first early-mid afternoon, then likely through MDW later in the afternoon, and eventually ORD by late afternoon/early evening.

VFR conditions are expected through the TAF cycle.

- Izzi

LOT WATCHES/WARNINGS/ADVISORIES

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