textproduct: Chicago

KEY MESSAGES

- Waves of showers will continue through tonight, with a soaking rainfall expected over much of the area before tapering off Wednesday morning.

- A return to more seasonable temperatures is expected late this week into the upcoming weekend.

DISCUSSION

Issued at 118 PM CST Tue Nov 3 2026

Early this afternoon, a deep, negatively tilted trough axis extends down the spine of the Plains. Along its leeward side, we find a couple of distinct areas of low pressure, most notably one currently lifting northeast into NW MO, and an extensive baroclinic zone/warm conveyor impinging on the Midwest along and ahead of the main surface cold front. Strong DCVA and quick upper height falls ahead of the deepening low make for a deeply dynamic system, especially upstream immediately east of the low level circulation. The storm also has plenty of layer moisture to work with as SPC mesoanalysis suggests between 1.5 and 1.7 inches of PWAT resides over much of IL this afternoon. Resultantly, a large area of showers is lifting north-northeast roughly near and west of the I-55 corridor as of 1 PM.

These showers will gradually spread eastward and fill in the remainder of northern IL by early evening, although areas east of I-57 may stay largely dry well into the evening. The most widespread rainfall is expected around our CWA during the evening and overnight while the strongest forcing focuses over our area. Embedded pockets of heavy rain are expected and a few thunderstorms may be possible as well, primarily during the evening. A few hundred Joules of elevated CAPE are anticipated around our western CWA into this evening as the aforementioned low lifts into eastern IA. The deep forcing and moisture should allow parcels to make good use of that, but still should only support isolated chances for a couple of embedded storms through the evening, mainly west of the Fox Valley. A big majority of deterministic camps paint at least localized stripes of near or over an inch of QPF through tonight. A few to several tenths is expected on a more widespread basis with the highest QPF largely favored across the western half of the CWA. The better dynamics will move away to the east by early tomorrow and take the higher shower coverage with. The surface cold front will move across the area during the day tomorrow and a few lighter showers may linger into tomorrow as it does, primarily through the morning. The latter half of Wednesday should be largely rain-free as a dry wedge advects in.

The southern flank of the vertically stacked low will park over the general area late Wednesday into Thursday as the system gets hung up over the upper Midwest. This may drive some lighter isolated showers mainly across our north Wednesday night into early Thursday. Chances increase again Thursday afternoon into early Friday as a secondary trough axis/cold front pivots across the region. High pressure then slides in bringing dry conditions to the weekend.

A strong low level wind field encompassing this storm will bring windy conditions to the next couple of days. The KLOT VWP as well as ACARS soundings out of Midway have been sampling around 45 to 50 kt of SSW flow down to 900mb since earlier this morning. At the surface, winds have regularly been gusting between 25 and 30 mph and as high as 35 mph at times. This will continue through mid-afternoon before easing slightly. Weak boundary layer static stability overnight with the stronger flow remaining just off the deck will keep at least breezy conditions going through the night. The cold advection with the front moving across tomorrow should allow us to efficiently mix more 20 to 25 mph SW gusts down to the surface for the late morning and afternoon. And another breezy day is in store for Thursday with that secondary front pushing across.

Highs tomorrow are forecast to range from the upper 50s in our west to the middle and upper 60s into NW IN as the cooler airmass feeds in from the west. We won't be seeing much blue sky over the next few days until the system ejects from the region late in the week. The coolest conditions over the next seven days are expected at the end of the week behind that secondary trough axis with daytime highs in the 50s Friday and Saturday and lows possibly getting down near freezing away from the city Friday and Saturday nights. A slight warmup is then favored for the early part of next week.

Doom

AVIATION /06Z TAFS THROUGH 12Z THURSDAY/

Issued at 1124 PM CST Tue Nov 3 2026

Key aviation forecast messages:

- SHRA to continue overnight with brief MVFR VSBYs at times.

- CIGs trend down through the night to MVFR and then potentially near IFR toward RFD by Wednesday AM.

Waves of showers are expected to continue lifting across the area through the overnight hours with VSBYs briefly dropping into the low-end MVFR to IFR range within a narrow ribbon of heavier showers. Ceilings are expected to steadily decrease to MVFR over the next few hours and remain through the end of the period, potentially near-IFR toward RFD.

Winds remain at least sporadically gusty out of the south southeast early this evening and expect gusts into the 20-25 kt range to continue through the overnight hours. A brief SSW wind shift may occur with the narrow ribbon of heavier showers as they move through. Winds then gradually trend more southerly and then southwesterly overnight into Wednesday morning, remaining breezy through Wednesday night.

There continues to be a signal for patchy drizzle during the late afternoon and evening timeframe on Wednesday. If this persists an introduction of VCSH or a PROB30 for -DZ may become warranted. Confidence remains too low to include with this update.

Petr

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...None. LM...Small Craft Advisory until 9 PM CST Wednesday for the IL and IN nearshore waters.