textproduct: Chicago

KEY MESSAGES

- Occasional chances for scattered rain showers will continue into next week. - Temperatures will gradually warm through Saturday before trending cooler early next week.

DISCUSSION

Issued at 111 PM CDT Thu May 7 2026

Expansive upper-level cyclonic flow remains entrenched across the Upper Mississippi River Valley, which is leading to a continuation of the generally cool and, at times, showery pattern. An upper-level shortwave propagating around the outer periphery of the cyclonic flow continues to pivot southeastward across the area this afternoon, which with steep lapse rates (500mb temperatures sampled near -28C on the 18Z DVN RAOB), is supporting widely scattered showers at press time. The highest coverage of showers through the afternoon and evening should generally favored near and south of I-80 (near a remnant boundary) and near the Wisconsin state line (near the core of the coldest mid-level temperatures). Southwest winds will remain gusty (30 to locally 40 mph) this afternoon, especially near showers where the deep layer of dry sub-cloud air will lead to efficient downward momentum transfer.

Tonight, coverage of showers should tend to favor areas south of Interstate 80 as additional subtle DCVA rides atop the aforementioned frontal boundary. A gradient in cloud cover will set the stage for a gradient in overnight lows, with values expected to fall toward the mid to upper 30s near the Wisconsin state line to the upper 40s near US-24. Patchy frost formation will be favored north of Interstate 88 and especially near the Wisconsin state line, though will withhold a Frost Advisory given the expectation for upper-level clouds to thicken toward daybreak (which may stall the downward dive in temperatures).

Tomorrow, another upper-level shortwave will pinwheel through the upper-level cyclonic flow and support the development of showers and perhaps a thunderstorm along the stalled frontal boundary. Forecast guidance continues to exhibit spread in the location of the boundary by tomorrow afternoon, though have noted a slight southward trend in the latest guidance. As a result, will paint low-end chance (20-40%) PoPs south of I-80 tomorrow, with the highest values near US-24. Elsewhere, partly cloudy skies and a modest push of low-level warm-air advection will help boost highs into the mid to upper 60s. Yet another upper-level shortwave will move across the region on Saturday, presenting another opportunity for a few showers. Temperatures on Saturday look to be the warmest of the past few days with highs in the upper 60s (north) to mid 70s (south).

Another reinforcing shot of seasonably cool air will follow the front Saturday night and result in a swift return to somewhat below average temperatures Sunday into the beginning of next week. With that said, ensemble guidance continues to advertise a strong signal for a notable warming trend by the May 16 to 17 timeframe, which is in line with climatology.

Borchardt / Izzi

AVIATION /06Z TAFS THROUGH 12Z SATURDAY/

Issued at 1202 AM CDT Fir May 8 2026

There are no aviation weather concerns anticipated through the period.

VFR conditions are expected through the period as the focus for showers today remains south of the terminals. Winds will be light (5 kt or less) and somewhat variable this morning, but directions should gradually focus into a south-southwesterly direction at 7 to 10 kt for the afternoon and evening hours of today. While we will have to keep an eye on the evolution of the lake breeze boundary this afternoon, all indications at this time continue to point at it remaining east of the main Chicago terminals.

KJB

LOT WATCHES/WARNINGS/ADVISORIES

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