textproduct: Chicago

KEY MESSAGES

- Low chance (15%) for patchy slick spots late tonight into early Tuesday morning outside of Chicago.

- Warmer and occasionally wet weather is in store from the mid to late week period onward. Confidence is higher in more widespread rain late Wednesday night into Thursday and again late Friday into early Saturday.

DISCUSSION

Issued at 1257 PM CST Mon Mar 2 2026

Through Thursday:

Early this afternoon, most of the area sits in the lower 40s beneath sunny skies. Easterly winds are keeping conditions several degrees cooler on the west side of the lake, including downtown. Dewpoints are all over the place but managed to mix down into the single digits to around 10 degrees in our northwest yielding some low RHs out that way. Luckily, generally light winds are keeping any fire weather concerns at bay. Mid- high level cloudiness will build during the late afternoon and evening as temps cool back into the 30s.

A developing mid level shortwave impulse is scooting east across the Plains this afternoon after spinning up off the lee of the Rockies early this morning. The wave will move into the Midwest late tonight bringing with it our next chances for precip. A leading vort lobe will move over the area very late tonight into early Tuesday morning and, with the help of some warm advection and modest upglide, most deterministic camps are resolving at least trace amounts of light rain or drizzle in pockets during that window. A wedge of low-mid level dry air may impinge on precip's ability to make it to the surface and could lead to isolated or spotty coverage. But a saturated layer atop the dry air featuring steep lapse rates and even a little bit of elevated instability may very well generate precip capable of punching through that dry air. While an inversion and warm layer just off the deck supports liquid precip, temperatures at the surface are forecast to be right around freezing, if not a couple of degrees below freezing. Should rain/drizzle fall into sub-freezing temps, a glaze of ice could result in spots. An increase in low-mid level cloud cover tonight ahead of the wave can hopefully help keep temperatures up a bit. Sub- freezing temps appear most attainable near and west of the Fox Valley. In the forecast, maintained slight chances for freezing rain in this area into early Tuesday and instances of slick travel will be possible here and there during the morning commute, especially off of highways and arterials.

Showers will remain possible during the morning as the wave gets sheared off atop the area. The better rain chances will be found across central IL where the better moisture and forcing will track near a strengthening baroclinic zone that will set up downstate. Meanwhile, drier air aloft with northward extent will continue to hinder precip chances across much of northern IL. Latest high res guidance favors nearly all measurable precip coverage south of I-80. Behind the low level trough axis passing during the morning, pressure rises and dry advection will further focus the greater precip potential across southern and central IL for the afternoon. The latest RAP and HRRR keep all precip just south of the CWA during the afternoon.

An axis of moist, confluent air feeding into that baroclinic zone is expected to keep a steady corridor of rain and possibly embedded thunderstorms churning across central IL for the latter half of Tuesday and into Wednesday. Coverage is favored to largely stay south of the CWA during this period, but there remains notable model support for portions of our south to be included in the steadier rainfall, at least at times, late Tuesday into Wednesday. Depending on how far north that baroclinic zone can lift, it's not out of the question that a couple of embedded thunderstorms could be found in our south as low level warm advection works to steepen up lapse rates aloft and generate some elevated instability. The thunder potential appears significantly better south of the local area.

Precip chances will expand across northern IL late Wednesday into Thursday as another shortwave tracks through the region lifting the baroclinic zone north. This will transport 1" of PWAT and some marginal instability into northern IL. Forcing doesn't look fantastic, but we will be in a favorable position relative to the jet max to see some appreciable, deep lift. These signs point toward a potential for some healthy showers Wednesday night and Thursday. Coverage locally remains a bit uncertain and will be influenced by the track of the low level wave, but a period of widespread showers is favored among guidance, namely in the Wednesday night through Thursday morning window. A few embedded thunderstorms may be possible during this period as well. Precip chances will come into a lull Thursday evening behind the departing system.

Doom

Thursday Night through Monday:

Rain chances look to temporally drop off for a period Thursday night as a region of forced large scale decent sets up overhead along the backside of the exiting mid-level impulse. This will be short lived. On Friday, mid-level southwesterly flow will strengthen as a mid-level jet ejects northeast across the Plains into the Upper Midwest. This will send a low amplitude mid-level shortwave racing northeastward into the Upper Midwest sometime late Friday morning or early Friday afternoon. Scattered showers and elevated thunderstorms accompanying this feature may impact parts of northern IL and southern WI into early Friday afternoon, but outside of this potential, it appears there will be a good amount of dry time during the day.

Temperatures on Friday are expected to soar well into the 60s to around 70 for most through the afternoon as a surface warm front surges northward across IL and IN. However, as is typical this time of year, onshore flow ahead of this front across far northeastern IL may keep conditions much cooler through much of the day until the warm front clears this area. The combination of these very warm temperatures and unseasonably high dew points, into the upper 50s to near 60, will support an unstable and well sheared warm sector in the wake of the earlier day storms. However, it appears there will not be much of a focus for much late afternoon and evening convection in our area following the earlier day impulse. Instead, shower and thunderstorm chances and coverage look to be the greatest late Friday into Saturday morning in association with a cold frontal passage.

Rain chances will come to an end following the cold frontal passage on Saturday, at least for a few days. Temperatures will generally remain well above average through early next workweek. Current medium to long-range ensembles point towards a stronger cold front passage bringing a return to colder conditions by later next week/mid-March.

KJB

AVIATION /00Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 532 PM CST Mon Mar 2 2026

MVFR cigs will gradually build across the region late tonight into Tuesday morning. There is an increasing potential for cigs to build down under 2000 ft Tuesday morning, but this remains a bit too low to warrant a mention of low-MVFR in the outgoing TAFs. Light southeasterly winds will continue tonight and Tuesday morning, becoming variable at times.

A passing disturbance may bring a small chance for some light precipitation to the terminals, roughly in the 10z to 17z timeframe. Guidance indicates the presence of some upper-level instability, which suggests some convective elements may develop aloft. At this time, it's unclear if these will be heavy enough to overcome pockets of dry air, with confidence a bit too low to justify PROB or TEMPO mentions at this time. If precip does materialize, surface temperatures will be near freezing but dewpoint temperatures will also be slowly rising, and suspect this will generally help mitigate icing impacts. A brief period of non-freezing drizzle may develop late Tuesday morning into the early afternoon.

Winds will eventually turn north and northeasterly Tuesday afternoon with MVFR expected to scatter to VFR late Tuesday afternoon into the evening.

Carlaw

LOT WATCHES/WARNINGS/ADVISORIES

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