textproduct: Chicago

KEY MESSAGES

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

DISCUSSION

Issued at 229 AM CDT Fri May 8 2026

A broad longwave trough centered near James Bay will remain the prominent feature across the Great Lakes region into early next week, resulting in several additional periods of isolated to scattered showers.

A WNW to ESE oriented mid-level front roughly around 600 hPa is interacting with an area of moisture marginally sufficient to generate an axis of showers across the southern CWA early this morning. Though lapse rates above this layer are under 6C/KM and IR cloud tops have remained mostly warmer than -20C, there have been sporadic GLM flashes and a few IC/CG lightning strikes over the past few hours. The axis of showers and perhaps a few more instances of lightning will drift eastward, remaining around or south of the Kankakee River, through daybreak.

A 700 hPa wave currently evident over the Nebraska panhandle early this morning will quickly track eastward today. Though surface-based moisture will be rather limited, deep mixing this afternoon will likely tap into a more robust area of low/mid- level moisture to the west to produce a growing area of high- based showers with a few embedded lightning strikes around/east of I-55 and south the Kankakee River Valley mid to late afternoon. Deep inverted-V profiles also suggest that some of the initial showers could be gusty before coverage increases late in the afternoon. Also cannot rule out some sprinkles along a slow-moving or stalled lake breeze boundary across northeast Illinois mid-afternoon, but better mid-level moisture and support will likely remain well south of this area.

Another (stronger) mid-level wave and cold front will cross the area through the day Saturday. Depending on the exact timing of the frontal passage, another period of isolated to widely scatted high- based showers are possible across primarily northeast Illinois and northwest Indiana mid to late afternoon. Yet another wave approaching from the west Saturday night could yield an axis of rain over the southern half of the CWA. Cooler and drier conditions are expected Sunday and Monday. With high pressure nearing from the northwest and dry conditions noted by PWATs under 0.3 inches, another unseasonably chilly night with some patchy/areas of frost for outlying area is in store Sunday night.

There are some hints in the extended guidance that broad ridging over the western CONUS will begin to edge eastward next week. However, decent agreement with a stronger trough (and rain chances) digging southeastward across the Great Lakes Tuesday into early Wednesday will likely re-inforce, or at least slow the departure of, the long-standing trough over eastern Canada.

Kluber

AVIATION /12Z TAFS THROUGH 18Z SATURDAY/

Issued at 602 AM CDT Fri May 8 2026

There are no significant aviation weather concerns anticipated through the period.

VFR conditions are expected through the period as the focus for showers today largely remains south of the terminals. Winds will be light (5 kt or less) and somewhat variable this morning, but directions will gradually focus into a south-southwesterly direction at 7 to 10 kt for the afternoon and evening hours. 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.