textproduct: Chicago

KEY MESSAGES

- A few showers are expected late this afternoon into this evening, mainly well northwest of a Chicago to Peru line.

- It'll be windy and unseasonably warm Tuesday.

- Showers are likely late Tuesday, Tuesday night, into Wednesday morning, with a good soaking rainfall expected over much of the area.

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

DISCUSSION

Issued at 137 PM CST Mon Nov 2 2026

A long wave trough over the U.S. Rockies into the Great Plains is moving slowly eastward. Water vapor imagery early this afternoon shows a pair of closed mid-upper level lows embedded within the broader trough. One located over the northern Plains will shear out/open up as it moves northeastward into a more confluent flow. An embedded lead shortwave trough in advance of this upper low over the Cornbelt is supporting a band of showers across Minnesota south into eastern IA and far NW IL. This shower activity is likely being aided by strong warm air advection in advance of an approaching warm front. The southern flanks of this shower activity will likely graze our northwestern and far northern CWA late this afternoon into this evening.

The aforementioned warm front extending from western MN southeast to the lower Ohio Valley will move northward tonight. In the wake of the warm front, temperatures and dewpoints will likely slowly rise into/through the 60s tonight. By sunrise Tuesday, temperatures will likely be in the low to mid 60s, which is about 10F above the normal highs for this time of year. Strong and gusty southerly winds will provide for a steady feed of unseasonably warm and humid (by Nov standards) air through the day Tuesday.

Low cloudiness will likely at least partially scatter out in the wake of tonight's warm front. Some breaks in the overcast or at least thinning of the overcast should allow temps to inch upward into the lower 70s over the eastern half or so of the CWA, including most of the Chicago metro area. If there is a bit more in the way of breaks in the cloudiness Tuesday, it is certainly plausible that highs could push into well into the 70s given the progged near record warm 925mb temps.

A tight pressure gradient will support strong and gusty southerly winds. Just how strong the winds get Tuesday will depend on the depth of mixing/how warm temps get. Showers will likely arrive in our western CWA Tuesday morning, this should result in high temps "only" in the 60s and will likely limit the magnitude of the winds and especially gusts some. Farther east where temps will be warmer, gusts of 30 to 35 mph are likely with some potential for some 40+ mph gusts with any more significant thinning of the cloudiness. Time window for the strongest winds/gusts should be mid morning through early to mid afternoon, with winds/gusts easing as cloud cover thickens and especially as rain spreads slowly eastward.

As for rain chances, they will be tied to the second closed mid-upper level low, which is noted on water vapor imagery approaching the OK/TX Panhandle region. This upper low is progged to move eastward today before rounding the base of the parent trough and lifting north later tonight into Tuesday. Strong synoptic forcing is expected as this embedded trough is progged to become negatively tilted as it moves north into the Cornbelt Tuesday afternoon and evening. This strong forcing coupled with PWATs near/just over 300% of normal should result in a large shield of showers, some locally heavy moving slowly east across the Mississippi Valley Tuesday. In our area, showers should arrive near/west of I-39 Tuesday morning, but with southerly mid-upper level flow, this activity should be slow to spread east across our CWA Tuesday. In fact, rain may hold off until after dark across eastern IL and northwest Indiana. Waves of showers are expected Tuesday night into Wednesday morning. Widespread rainfall totals of a half inch to an inch are expected, heaviest totals likely over western CWA.

Upper level pattern across the country is progged to get quite blocky during the middle and end of the upcoming work week. The result looks to be the upper low over the Cornbelt getting stuck meandering around the Midwest/western Great Lakes. Smaller scale vorts pivoting around this meandering upper low will likely result in periodic showers through at least the remainder of the work week. Timing of these individual impulses rotating around the upper low are hard to pin down. There will likely be many rain free times in between some showery periods.

A return to more seasonable temperatures is expected after tomorrow's warmth. A cold front will usher in a cooler, Pacific origin air mass Tuesday night into Wednesday. Cloud cover and lingering rain will likely result in near steady if not slowly falling temps Wednesday, but still a bit above the mid 50s averages for early November. Cloud cover and some wind will likely limit the diurnal temp swings Wednesday night through Saturday. NBM low temps appear significantly too cool with nighttime lows, especially Thursday night and Friday night. Later forecasts will likely need to bump those lows up into the 40s with daytime highs inching up mostly into the lower 50s by later this week into the first part of the weekend.

- Izzi

AVIATION /00Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 633 PM CST Mon Nov 2 2026

Key Messages:

- IFR ceilings are expected tonight with MVFR ceilings then possible through most of the rest of the TAF period.

- Pockets of drizzle and associated sub-VFR visibilities may affect some or all of our TAF sites tonight.

- Shower chances increase with time over the course of the TAF period.

- Gusty southerly winds will develop Tuesday morning and persist through the remainder of the TAF period.

An abundance of low-level moisture will result in reduced flight categories tonight. IFR ceilings are draped over most of our TAF sites at press time and likely won't improve for several more hours, but a return to MVFR ceilings is likely by the early-mid morning tomorrow. Some of the latest forecast guidance favors VFR conditions to return to our Chicago metro TAF sites by the mid-late morning (highest chances for that at GYY), but the lower ceilings are expected to slosh back eastward Tuesday evening and result prevailing in sub-VFR conditions once again Tuesday night.

Modest low-level isentropic ascent has also fostered the development of some pockets of drizzle in northern and central Illinois at the time of this writing. This drizzle may affect some or all of our TAF sites at times tonight and result in periods of MVFR or IFR visibility. Bona fide rain showers will then spread over the area from west to east tomorrow as a frontal zone slowly creeps towards the area. RFD may see periods of rain showers from Tuesday morning onwards. During the afternoon, these showers may briefly be heavy, and there is about a 20% chance or so for some isolated lightning strikes to occur near RFD as well. The Chicago metro terminals could be affected by some of this shower activity as early as Tuesday afternoon, but the greater chances and coverage of rain there will hold off until towards (and especially beyond) the end of the current set of TAFs.

Lastly, southerly winds are expected to prevail through most of the TAF period and will become stronger/gustier Tuesday morning as the frontal system and an associated area of low pressure approach the area. 15-20+ kt sustained winds and gusts in excess of 30 kts may be observed at times tomorrow as a 50+ kt low-level jet sets up over the area.

Ogorek

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...None. LM...Small Craft Advisory until 6 AM CST Wednesday for the IL nearshore waters.

Small Craft Advisory from 9 AM Tuesday to 6 AM CST Wednesday for the IN nearshore waters.