textproduct: Chicago

KEY MESSAGES

- Isolated to widely scattered showers and perhaps an isolated thunderstorm or two remain possible through late this afternoon in areas east of I-57 and near/south of the Kankakee River.

- Periods of showers and/or drizzle are expected at times Friday through this weekend (greatest chances/coverage expected Friday night through Saturday morning).

- Additional periods of wet weather are likely next week.

DISCUSSION

Issued at 201 PM CDT Thu Oct 29 2026

A cold front is tracking southeastward across our forecast area at the time of this writing. Some pre-frontal convection that developed and affected areas near and east of I-57 a little while ago has since moved off to our east into IWX's CWA. GOES satellite imagery shows that cumulus in the trailing portion of the same pre-frontal confluence zone is still attempting to grow, and additional isolated to widely scattered shower and thunderstorm development could still in our far southeastern CWA over the next few hours. However, the convergence/confluence here isn't quite as good as it was earlier farther to the north, so not anticipating any greater convective coverage in our CWA through the remainder of this afternoon.

Heading into Halloween weekend, a couple of disturbances of Pacific origin are expected to lift northeastward into the Midwest. While these disturbances are progged to remain somewhat disorganized, their arrival -- paired with modest isentropic ascent, broad synoptic forcing within the right entrance region of a 100+ kt upper- level jet streak over the Great Lakes, and an associated influx of tropospheric column moisture -- will result in some showery/drizzly periods through the weekend.

The first raindrops could be seen in our forecast area as early as midday tomorrow, though with dry low-mid-level air to work through and the better forcing still lagging to our southwest, much of the area likely won't see any measurable rainfall until Friday night into Saturday morning as the more coherent forcing and better moisture spreads into the area. Couldn't rule out a few isolated lightning strikes occurring during this Friday night into Saturday morning time period as slightly steepened mid-level lapse rates attempt to creep into our CWA. However, forecast soundings indicate that most of any associated meager instability should remain concentrated below the -20C level -- suggesting that even the taller convective cells may struggle to achieve electrification. Deterministic and ensemble guidance broadly suggests that the shower activity should tend to decrease in coverage going into Halloween evening, though at this time, it remains possible that at least isolated pockets of rain and/or drizzle could manage to hang around past sunset and affect trick-or-treating activities for some. Additional periods of rain and/or drizzle may be seen in our area on Sunday as well, though forecast confidence in this is lower compared to Saturday.

Early next week, multiple additional upper-level disturbances are expected to conglomerate somewhere over the western or central CONUS and yield a slow-moving, high-amplitude composite longwave trough. The exact details of how everything will come together remains unclear at this time, but it's likely that we'll see additional rainy periods next week as this troughing meanders towards and across our longitude. Temperatures for next week will also largely hinge on the evolution of this trough and when any associated rainfall works its way through our area.

Ogorek

AVIATION /18Z TAFS THROUGH 00Z SATURDAY/

Issued at 1214 PM CDT Thu Oct 29 2026

A cold front will continue to shift through the region this afternoon, turning winds out of the northwest. Some gusts near 20 kts may accompany the initial wind shift, but winds will ease through the late afternoon and evening. MVFR cigs will be possible at the Chicago-area terminals through about 21-22z.

Light northerly winds will eventually become northeasterly late tonight into early Friday morning. Another disturbance will approach the area tomorrow afternoon resulting in an increase in VFR cloud cover through the day. While some sprinkles will be possible after about 21z on Friday, both chances and impacts appear too limited to warrant any formal precipitation mentions in the extended ORD/MDW TAFs at this time.

Carlaw

LOT WATCHES/WARNINGS/ADVISORIES

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