textproduct: Chicago

KEY MESSAGES

- 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 /00Z TAFS THROUGH 06Z SATURDAY/

Issued at 633 PM CDT Thu Oct 29 2026

Forecast concerns include...

Wind shift to northeast early Friday morning. Chance of showers late Friday evening into Saturday morning.

Northwest winds under 10kts will become more northerly late this evening and then shift to the northeast before daybreak Friday morning. Wind directions will then become easterly during the day Friday and remain easterly for the rest of the period.

There will be a small chance for a few showers or sprinkles late Friday afternoon into Friday evening, mainly across northwest IL but there will be a better chance for showers and perhaps periods of rain late Friday night through midday Saturday. Mvfr level clouds will be possible during this time. cms

LOT WATCHES/WARNINGS/ADVISORIES

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