textproduct: Chicago

KEY MESSAGES

- Above average temperatures expected to continue through the upcoming weekend, though tomorrow looks like the warmest day of the bunch.

- While not a wash out, there will be some periodic chances for showers and perhaps isolated thunderstorms at times late Wednesday night through the upcoming weekend.

DISCUSSION

Issued at 1243 PM CDT Tue Oct 27 2026

The rest of the afternoon looks fairly quiet and cloudy as a moisture-starved upper-level waves (currently lifting across the IA/MO border) traverses into the Lower Great Lakes. Suppose a sprinkle or two cannot be ruled out (roughly a 10% chance for rain at any given location).

Wednesday is shaping up to be unseasonably mild area-wide. High temperatures are forecasted to reach the low to mid-70s during the afternoon amidst breezy southwest winds (gusts up to 25 mph, especially with northwestward extent).

The next notable shortwave impulse is expected to track well north across southern Canada Wednesday night. As an associated surface low moves eastward across Ontario, a southwestward- trailing cold front will push southward into our area by Thursday. Although the strongest large-scale forcing will pass well to the north, pooling low-level moisture (dew points in the mid to upper 50s) along the frontal boundary could support isolated to widely scattered showers, particularly late Wednesday night into Thursday. Consequently, we maintain low- end (20 to 40%) chances of precipitation during this period.

Temperatures Thursday and Friday look to be stunted by extensive cloud cover and onshore winds. Have aggressively undercut NBM guidance to now feature highs generally in the mid 60s to around 70 on Thursday to solidly in the 60s on Friday (more more in line with ensemble guidance). Some deterministic guidance suggests highs may struggle to climb out of the 50s on Friday near the Wisconsin state line and Lake Michigan shoreline.

Ensemble guidance suggests a series of impulses will track from Mexico east-northeastward into the Lower Great Lakes region during the weekend, followed by a potentially more substantial system tracking slowly across the central U.S. next week. As a result, there will be daily chances for rain from Saturday into next week. Dry periods are still expected, so it will not be raining continuously throughout the weekend.

KJB/Borchardt

AVIATION /00Z TAFS THROUGH 06Z THURSDAY/

Issued at 617 PM CDT Tue Oct 27 2026

No significant aviation forecast concerns for this forecast period. Only items of note are a period of breezy south winds Wednesday afternoon, and a marginal LLWS potential later Wednesday night (mainly beyond the end of this forecast).

The forecast area remains between surface high pressure to the east, and a cold frontal trough and area of low pressure across the High Plains to our west. In between these features, a gradually tightening surface pressure gradient will result in light southeast winds becoming south overnight. These south winds will become somewhat breezy by early Wednesday afternoon, with gusts near 20 kts especially mid-late afternoon and then easing toward sunset. A southwesterly low-level jet is forecast to develop later Wednesday evening, with southwest winds nearing 45 kts after midnight (just beyond the end of our 30-hour ORD/MDW forecasts). Surface winds will likely drop to less than 10 kt during the evening, but may increase and even develop sporadic gusts overnight. If so, this may make for marginal LLWS conditions.

Otherwise, VFR conditions are expected to persist, with thicker mid/high level cloud cover eventually lowering a bit into the 8-12 kft range overnight in association with a mid-level disturbance lifting across the area. Some upstream radar returns with these clouds are indicative of virga (precip aloft), evaporating prior to reaching the ground. Cloud cover should decrease toward morning.

Ratzer

LOT WATCHES/WARNINGS/ADVISORIES

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