textproduct: Chicago

KEY MESSAGES

- Quick warm-up for the end of the week, with dry, windy and very mild weather expected Friday. These conditions may result in a heightened grass/brush fire danger Friday afternoon.

- Colder with some additional snow chances over the weekend and into early next week.

DISCUSSION

Issued at 239 AM CST Thu Feb 26 2026

Through Friday Night...

Main weather concerns through the period include snow ending predawn across our far southern cwa, then a dry, windy and much warmer day on Friday. Warmth, winds and low humidity Friday will likely lead to another heightened grass/brush fire spread potential.

Regional radar imagery indicates an area of snow exiting our far southern tier of counties, after producing a quick period of moderate snow with some minor accumulations noted on roadways per webcams along our border with ILX. Snow will continue to shift off to the southeast prior to sunrise, in association with a mid-level short wave tracking southeast into the lower Ohio Valley. Cloud cover lingers to the west/northwest of the departing wave as far back as IA/southern MN, and will linger across the region this morning before decreasing midday/afternoon as stronger deep-layer subsidence develops. At the surface, weak high pressure centered over southern Lake Michigan/southwest lower Michigan will drift east this morning, allowing winds to turn southwest this afternoon. Speeds will be modest, though some gusts into the 15-20 mph range appear possible across northwest IL, where the gradient will tighten just a bit. Warm advection developing aloft, combined with the modest southwest winds and some sunshine this afternoon should allow temperatures to recover into the low-mid 40s across much of the forecast area.

Tonight, a potent mid-level short wave is progged to dig southeast across the Canadian prairie provinces, with a deepening surface low developing to the Manitoba/Ontario border region east of Lake Winnipeg by morning. A broad area of surface pressure falls is forecast southeast of the ~990 mb low, extending across the upper Midwest and increasing warm advection aloft on a westerly 25-30 kt low-level jet. Mostly clear skies should allow for winds to decouple across our area during the evening, with temperatures falling into the upper 20s/lower 30s overnight with light southwest winds.

The stout wave to our north is expected to continue to amplify across the northern Great Lakes on Friday. While the surface low passes north of Lake Superior, associated surface pressure/height falls are forecast to further strengthen the west-southwest low level jet into the 40-50 kt range. Forecast soundings vary with their mixing depth during the midday/afternoon hours, though it looks like we'd likely be able to mix down 30-35 mph gusts - and potentially stronger gusts if we mix more deeply. Temperatures are expected to easily reach the low-mid 60s during the afternoon, and potentially near 70 along with lower surface dew points if deeper mixing occurs. Have boosted surface winds/gusts and lowered surface dew points from NBM delivered guidance, and will have to monitor trends for a further heightened grass/brush fire spread potential. See Fire Weather section of this discussion below.

As the surface low moves further east across Ontario late Friday, a trailing cold front will move into northern IL late, and will push southeast across the area Friday evening/night. Winds will ease and shift northwest, though will likely remain somewhat blustery overnight in the low-level cold advection regime. Temperatures thus will fall into the 30s/40s with wind chills dipping into the 20s by midnight after 60-degree warmth Friday afternoon.

Ratzer

Saturday through Thursday...

Toward the end of the week, model guidance is in agreement on a shortwave clipper disturbance rounding the base of the broad upper trough as it transects the northern CONUS. This feature will steer directly into northern IL early Saturday bringing a clip of accumulating snow showers nearby. All deterministic camps, with the exception of the GFS, now track the primary axis of snowfall, with accumulations between one and two inches, just to our north across southern WI with generally less than inch favored south of the state line. Some even suggest that antecedent low level dry air may be too much to support much precip development across a big majority of our CWA. There's plenty of support though for at least light snow showers and flurries around most of the area, but chances do generally look worse with southward extent. If precip falls in our southern CWA, it's could be in form of rain or a wintry mix. Time window for snow on Saturday is roughly mid-morning into the early evening.

Still looking like a potentially active stretch of weather around the region next week, starting with a system in the Sunday-Sunday night window which shows potential to bring noteworthy wintry impacts to parts of the region. Guidance has come into better agreement recently with where to track the storm and the corridor of highest snow totals, but there's still much to be ironed out. For several runs, the GFS had previously been wanting to steer a widespread several inches of snowfall across northern IL. Well over the last 24 hours, the GFS and its ensemble counterpart have been on a big southward trend and now even track the storm farther south than most other available guidance. The deterministic Euro has been, and continues to be, remarkably consistent although the ENS isn't nearly as sure. All latest deterministic camps now bring the highest snow totals across central IL, and some rope southern portions of our CWA into that corridor. But there remains quite a lot of spread among ensemble members including a notable amount of support still for the main axis of snow to track across northern IL. It does appear though that the trend is for central IL to be the most impacted from this system. A few to several inches of accumulation are favored in the main corridor of snowfall. It's tough to say the northern extent of snow coverage with some dry layer air still infiltrating from the east diverging from a Great Lakes high. Snow showers Sunday to Sunday night will be possible area-wide, but too early to get specific on impacts for any given area.

A tight baroclinic zone will get locked up across the Midwest next week and steer a number of waves nearby, so we'll see at least a couple of more opportunities for rain and snow next week. Expecting seasonably cool conditions through early next week, but guidance strongly favors a warming trend for mid-late week.

Doom

AVIATION /12Z TAFS THROUGH 18Z FRIDAY/

Issued at 600 AM CST Thu Feb 26 2026

Key messages for the 12Z TAF period:

* Gusty SW winds on Friday

Light winds will vary in direction this morning veering around the east side of the compass before going SW by late morning. Sustained winds will get up to around 10 kt with gusts into the teens kt this afternoon. Winds look to subside tonight, but may try and stay up at around 10 kt. They'll ramp up out of the SW Friday morning with gusts into the 25 to 30 kt range for the mid-late morning.

VFR is expected throughout the period.

Doom

LOT WATCHES/WARNINGS/ADVISORIES

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