textproduct: Chicago

KEY MESSAGES

- Scattered showers with an isolated thunderstorm possible through the end of the afternoon.

- Chance of showers Saturday night/Sunday morning east of I-55.

- Active pattern next week with showers and possible thunderstorms, then turning colder into next weekend.

DISCUSSION

Issued at 213 PM CDT Fri Oct 9 2026

Widely scattered showers are moving across parts of northern IL early this afternoon. These showers have largely formed along an elevated baroclinic zone on the leading edge of a warm advective push. The highest concentration of showers is found near and north of I-90 as they approach the Fox Valley as of 2 PM. Highest coverage is expected to continue across our far north and into southern WI through the remainder of the afternoon with generally lesser coverage farther south, but most of the Chicago metro is in for at least a brief round of light rain before the end of the afternoon. There were previously some embedded storms as these showers moved across northwest IL, but lightning coverage has since retreated up into southern WI and thunder chances locally through the afternoon will be low, highest near the WI state line. One exception is a persistent narrow corridor of showers and embedded thunderstorms that has been stirring near our southwestern CWA border for a couple of hours along a defined confluence axis. This feature is expected to make little headway toward the northeast into parts of Livingston and LaSalle counties as it gradually fizzles away through mid-afternoon.

The area should be rain-free for the evening and mostly cloudy skies will clear out to the east. Temperatures are expected to drop into the 50s by early tomorrow and stay closer to 60 in and around the city. Though we'll be parked beneath a stout nocturnal inversion, a low level jet just off the deck with as many as 30 to 35 kt of flow at 975 mb should bring marginally breezy conditions overnight with occasional gusts north of 20 mph possible. High-level cloud cover is expected to fill in from the southeast beginning tonight ahead of the remnant hurricane.

No precip is anticipated tomorrow, but cloud cover will continue to expand around the area through the day. Tomorrow will be a warm one with highs in the upper 70s and lower 80s and a southerly breeze. Temperatures on Sunday will range from the lower 70s in our east with thicker cloud cover and a chance for light rain to the upper 70s out west toward I-39. Light showers will be possible Saturday night and Sunday morning primarily east of I-55, although an isolated shower can't be ruled out as far northwest as I-55 and up into the city.

A broad center of low pressure is favored to track nearby and drag a cold front across the region early next week. Accordingly, we find a chance for scattered showers and embedded thunderstorms from Monday evening into early Tuesday. Warm advection ahead of the system is expected to bring more unseasonably warm temperatures to Monday with highs forecast in the 80s area-wide, including upper 80s possible across the outlying areas. More seasonable conditions are then favored through the rest of the work week. Additional rounds of precip are expected in the Wednesday through Friday window with a series of disturbances progged to move across the region.

Doom

AVIATION /18Z TAFS THROUGH 00Z SUNDAY/

Issued at 1226 PM CDT Fri Oct 9 2026

Aviation forecast concerns:

- Period of showers this afternoon with a 15-20% chance of isolated thunderstorms (highest at RFD, decreasing with east/southeastward extent).

Midday surface analysis places a warm front across central IA, extending east-southeast into central IL. North of this front, elevated SHRA/embedded TSRA were occurring from northeast IA and southwest WI into northern IL, in response to ascent atop the warm frontal slope ahead of a mid-level wave tracking across IA. The leading edge of this precipitation has been slow to develop eastward, as it moves into drier air across the forecast area and away from the axis of elevated instability along the MS river. Showers/embedded TS will continue to shift east this afternoon however as the aforementioned wave approaches, though with the eastern edge of the instability pool only forecast to make it to the Chicago metro area the TSRA coverage is likely to be on the low side. Give the TS threat is non-zero, elected to maintain the PROB30 mention. All of this activity should eventually move east of the terminals by 23-00Z. VFR conditions are otherwise expected to prevail through the period.

Surface winds are expected to be generally south-southeast to southeast to the north of the warm frontal boundary into tonight, eventually turning more southerly Saturday. These south winds will likely become somewhat breezy during the day, with gusts approaching 20 kts. These may be tempered somewhat however, by a thickening high cloud shield on the northern fringes of hurricane Isaias.

Ratzer

LOT WATCHES/WARNINGS/ADVISORIES

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