textproduct: Central Illinois

KEY MESSAGES

- Seasonably cold conditions continue, with highs only in the teens today. Wind chills will be around 10 degrees below zero late tonight into Saturday morning.

- There is a chance (20-40%) of lake effect snow showers this evening, with chances highest north of I-74. These showers could lead to localized visibility reductions and a dusting of snow.

- Light snow is also possible Sunday evening (20-30%). Accumulations are unlikely to exceed one inch, but untreated roadways could become slick.

- Another system could bring wintry precipitation to central and southeast Illinois Tuesday into Wednesday, with potential for areas of snow and ice accumulations. It is too soon to determine where specifically the snow or ice accumulations will occur.

DISCUSSION

Issued at 311 AM CST Fri Jan 30 2026

A broad, 1042-mb sfc high pressure was located over the Canadian Prairie at the start of the period. With clear skies and light (less than 10 mph) northerly winds across the ILX CWA, temps have fallen below zero in some spots along/north of the I-72 corridor. Wind chills of 5 to 15 below zero are forecast through early this morning, with wind chill values rising above 0 degrees by midday.

*** TODAY ***

An east-west oriented upper trough axis currently over the Upper Midwest is set to dig south today. Even by January standards, this trough features notably cold temps at 850mb with values around -20 degC moving into the ILX CWA this afternoon, which is below the 10th percentile of the observed sounding climatology for late January. These cold temps will result in steep lapse rates through the PBL.

As this trough swings into the ILX CWA this afternoon/evening, expect increasing cloud cover along with scattered flurries and the potential for a few snow showers. The ambient airmass remains quite dry, with PWAT values below 0.15" sampled by the 30.00z KILX sounding, but fetch off Lake Michigan will aid the snow shower development. An investigation of forecast guidance for snow squall ingredients suggests that squalls are unlikely today. Low-level (0-2 km) mean winds are just below 20 kts (typically want values above 25 kts), and the instability fields are subpar despite the steep lapse rates. The snow showers could still lead to some visibility reductions this afternoon, and perhaps a quick dusting of snow in some spots. The probability of measurable precip remains low, around 20% per the latest HREF. Any snow showers that do develop will generally be tracking from north to south, gradually weakening with southward extent.

Seasonably cold temps persist today, with highs only forecast to reach the mid-teens.

*** TONIGHT INTO SATURDAY ***

The aforementioned sfc high pressure shifts south, becoming centered across the eastern Plains tonight while cyclogenesis occurs off the coast of the Carolinas. That sfc pattern will lead to modest northwesterly flow (10-15 mph) across central IL overnight into Sat AM. The presence of cloud cover should keep temps above zero, but wind chills may still fall near advisory criteria for a few hours early Sat AM.

Most of the area will be dry overnight and through Sat, although a lingering lake effect snow band can't be ruled out in far eastern IL (east of I-57). Lake Michigan water temps are in the mid 30s, which combined with the cold air aloft leads to moderate lake- induced instability. There could be a lingering lake-effect snow band near the IL/IN border Fri night into Sat AM. For now, forecast guidance supports the band staying ever so slightly east of the ILX CWA, but even a small westward shift in placement will warrant an increase in PoPs. If this snow band were to clip parts of eastern IL, a few tenths of snow accumulation could occur, but amounts are unlikely to exceed 1".

*** SUNDAY INTO NEXT WEEK ***

A weak clipper approaches on Sun, and forecast soundings continue to suggest a period of light snow during the evening. Saturation is not particularly deep, nor the ascent particularly strong, but there could still be some (very) minor accumulations. The latest NBM has just a 20-30% chance for 0.1" and under a 10% chance of 1", but with cold ground temps this snow could result in any untreated surfaces becoming slick.

For much of next week, high temps are expected to be in the upper 20s or low 30s. Another wave approaches on Tues, and there will be better moisture advection off the Gulf oriented towards our area. Unlike the last several systems, there is uncertainty about precipitation type with this system, as forecast soundings indicate a low-level warm nose (with temps above freezing at times). Depending on the sfc temps, this could lead to some areas within central/southeast IL experiencing freezing rain.

Confidence in any details for this Tues-Wed system are low at this range, and deterministic models continue to exhibit a broad envelope of low tracks falling somewhere within the mid-MS or TN Valleys. From the probabilistic lens, the latest NBM has roughly a 5-10% chance of over 0.01" of ice and a 20-40% chance of 1" of snow (increasing with northward extent). While these probs don't jump off the page, that's due to the spatial uncertainty lowering the probs. There is potential for impactful snow accums with this system, and the NBM has a 5-15% chance for over 6" of south north of I-70. The deterministic model solutions do offer some insights to the potential evolution of this system, suggesting that there will be a broader, roughly east-west oriented corridor of snow accums along with a narrower, similarly oriented corridor of ice accums to the south of the snow. We're still a long way from being able to confidently determine where these corridors of wintry precip occur, and it could still miss our forecast area entirely (20-30% chance of no precip at any point during the Tues- Wed period).

Guidance depicts another clipper system swinging through late in the work week, offering another chance for precip although probs increase as you move north into the upper Midwest. Spread in the forecast temps is quite broad this deep into the forecast period, with the NBM suggesting highs anywhere from the upper 30s to low 20s. I'd lean towards the cooler half of the range given the expectation of the late week clipper and CAA behind it. Unfortunately for those of us seeking warmer temps, the chance of highs above 40 degF is less than 30% each day through Mon Feb 9th.

Erwin

AVIATION

(For the 12z TAFs through 12z Saturday Morning) Issued at 520 AM CST Fri Jan 30 2026

Main concern this TAF period is the potential for scattered snow showers to lower visibility and ceilings this evening, with the best chance of these being at the I-74 terminals between 00-03z. Included MVFR vis and ceilings in a PROB30 group for these sites, but if directly impacted by a snow shower would not be surprised to see vis below 2 miles. Winds will be out of the north through most of the day, then shift to northwesterly late in the period.

Erwin

ILX WATCHES/WARNINGS/ADVISORIES

None.