textproduct: Chicago

KEY MESSAGES

- Strong southerly winds, potentially gusting over 40 mph, are expected late this morning into this afternoon and may result in a heightened grass fire danger.

- Monitoring potential for accumulating snow somewhere in the region in the Wednesday night-Thursday morning timeframe. Areas south of I-80 and especially into central IL are most favored for impacts, but confidence remains shaky.

DISCUSSION

Issued at 303 AM CST Tue Feb 24 2026

Through Wednesday...

Main forecast concerns today are strong and gusty south winds and the potential for a heightened threat of grass/brush fire spread. For more on that, see the separate fire weather section of this discussion below.

Recent surface analysis depicts weak surface high pressure ridge from the lower Ohio Valley into southwest lower Michigan. Farther to our northwest, a deepening 995 mb surface low was located along the Manitoba/North Dakota border. Surface winds have backed to the south across the area west of the ridge axis, where the gradient was tightening up in response to strong pressure falls in excess of 5 mb/3 hr east/south of the low. The surface low is progged to track east-southeast into the northern Great Lakes by this evening in association with an amplifying mid-level short wave, inducing a 45- 50 kt south- southwesterly low-level jet across our region. Surface winds will thus increase after sunrise, with gusts in the 35-40 mph range likely during the late morning and afternoon hours. Can't rule out some gusts into the 45-50 mph range later this afternoon along and east of the I-55 corridor, where RAP/HRRR soundings briefly mix into 45+ kts at the top of the boundary layer, though thickening mid- level cloud cover may temper mixing this deeply and suspect that gusts above 40 mph would be sporadic if they occur. Gusts will gradually ease toward sunset as the low-level jet shifts east and the surface pressure gradient weakens in advance of a cold frontal trough.

With the best moisture and forcing passing north of the area, precipitation chances aren't too impressive today given the dry air in place across the region. There continues to be a signal in guidance however, for some saturation down into the 850-750 mb layer (noted in isentropic 290-295 K surfaces) ahead of the approaching cold front late this afternoon and evening. While column wet bulb profiles are rather cool due to drier low- levels, light precipitation rates will not likely support strong evaporative cooling. In addition, surface wet bulbs above freezing and air temps from the upper 30s to lower 40s should support mainly a brief period of spotty light rain or sprinkles (with perhaps a few wet snowflakes mixed in) mainly across north/east parts of the forecast area ahead of the cold front. Behind the front, winds will turn westerly and gradually ease this evening, though it will remain blustery overnight with 20-25 mph gusts at times and temperatures falling into the 20s as skies clear from the northwest.

Wednesday should start off sunny, though cold and still blustery with wind chills in the single digits and teens early in the morning with. Highs look to range from the lower 30s along the IL/WI border to near 40 across our southern counties, and winds will continue to slowly diminish through the day. Cloud cover will then increase from the west in the afternoon ahead of the next approaching disturbance.

Ratzer

Wednesday Night through Tuesday...

Still keeping an eye on the Wednesday night - Thursday morning window for a storm system to move through the region and bring the potential for accumulating snow to parts of the area. If you've been keeping up with the forecast, you'd know that guidance was recently struggling with the evolution of this system, but there has been a great improvement over the past 24 to 36 hours. Deterministic and ensemble guidance from the GFS, ECMWF, and CMC strongly favor the loosely organized surface low tracking across the lower Midwest and a potential for accumulating snow primarily across central IL. Ensemble PoPs have been on a steady southward trend as confidence builds. Between the latest iterations of the GEFS, EPS, and SREF, probs for measurable QPF are down to roughly 20% or less north of I- 80 and top out near 50% in our far south. The NAM continues to track the storm and accumulating snowfall farther north than the global camps. A few other CAMs that are now looking out into that period show something similar to the NAM, the RAP and HRRR not included. So there remains enough support, notably among some of the available regional and high res guidance, where I don't think anywhere near/south of I-80 is quite out of the woods yet for potential wintry impacts, but our far southern CWA and areas farther south appear most susceptible at this time.

Still a good deal of uncertainty in snow coverage north of the low track. An abutting high moving across the Great Lakes immediately north of the storm track may help hinder precip development locally. The latest extended RAP and HRRR, both looking into Wednesday night, center this feature right over northern IL and keep all precip south of the CWA through then. Another signal worth watching is one for an axis of strong deformation and frontogenesis on the north side of the storm which could result in a corridor of relatively higher snow totals. This is reflected in some model snow output, but such a feature would also be favored to track across central IL, possibly clipping our far south. Worst case scenario among latest deterministic camps is a swath of 1 to 2" accumulations a few counties wide with localized embedded few inch totals. Meanwhile, accumulating snowfall is looking increasingly unlikely for areas north of I-80. Wherever the axis of accumulating snow does set up will be susceptible to a slippery Thursday morning commute.

Warm advection ahead of an upper Midwest low will bring noticeably milder conditions to Friday with highs forecast in the 50s around the area. Cooler conditions are then expected this weekend, especially on Sunday with a bit of spread in Saturday's temperature guidance. A rather active synoptic pattern looks to stir up for this weekend into next week with a series of waves possibly tracking through the region in quick succession bringing frequent chances for rain and snow, including a growing signal for accumulating snow showers during the day on Saturday. Lots of variability in how that all plays out, so will leave it at that until confidence can grow.

Doom

AVIATION /12Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 540 AM CST Tue Feb 24 2026

Key messages for the 12Z TAF period:

* Gusty SSW winds today

* A low chance for a few light VFR showers or sprinkles this afternoon

Near-southerly winds will favor just west of south (190-200) as they build through the morning, gusting to over 20 kt by 14Z and in the 30 to 35 kt range during the late morning and afternoon. A few gusts to near 40 kt will be possible. Direction will veer to westerly this evening as winds stay breezy, but subside for the night and Wednesday morning to gusts to around 20 kt.

A low chance for some light rain or sprinkles exists at all sites this afternoon. Between the low potential and lack of possible impacts, opted to leave precip mention out of the TAFs. Expect VFR throughout the period.

Doom

FIRE WEATHER

Issued at 303 AM CST Mon Feb 23 2026

Most of northern Illinois has been quite dry over the past several weeks, and with no significant snow cover recently this has left fuels quite dry. Strong southerly winds developing today, combined with these dry fuels, will result in a heightened grass/brush fire danger across most of our northern Illinois counties this afternoon. While extensive cloud cover is expected to keep minimum relative humidity levels mostly above critical levels, any unexpected significant breaks in the overcast could result in milder temperatures and relative humidity levels at least briefly dropping below critical red flag thresholds. With this looking like a low probability of occurring, we still have no plans for a fire weather watch or red flag warning for this afternoon at this time.

Izzi/Ratzer

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...None. LM...Gale Warning from 9 AM this morning to 6 PM CST this evening for the IL and IN nearshore waters.