textproduct: Central Illinois

KEY MESSAGES

- Wind chills fall below zero this morning and Sunday morning, then temperatures moderate a bit into next week, with high temperatures between the mid 20s and mid 30s and wind chill values staying above zero.

- There is a 30-50% chance of light snow on Sunday, mainly north of a Jacksonville to Danville line. Snow accumulations are unlikely to exceed one inch, but the light snow may still result in slick road surfaces.

- Another system could bring wintry precipitation to the region on Tuesday. The probability of accumulating snow decreased from previous forecasts, and there is now just a 20% chance for over one inch of snow with this system.

DISCUSSION

Issued at 202 AM CST Sat Jan 31 2026

*** THROUGH EARLY SUNDAY MORNING ***

A potent upper level trough, evident in IR satellite imagery near the far southern tip of IL as of 07z/1am, continues to dig towards the Carolinas. An expansive, 1042-mb sfc high pressure was centered over eastern Nebraska at the same time. Friday evening, the low- level (925-700mb) wind fields supported lake moisture advecting south and supporting flurries/light snow showers across the ILX CWA. These have generally waned over the last few hours as the upper low shifts southeast and the mean low-level flow takes on more of a southerly component, directed towards the IL/IN border.

The cloud cover associated with this moisture has helped keep temperatures several degrees warmer than expected, although NT microphysics satellite imagery suggests the thicker clouds are becoming much less widespread. Persistent northwesterly flow (10-15 mph) will still push wind chills to around 10 below through early morning, but with the slightly warmer temps its looking less likely that we approach wind chills of 15 below.

Much of the area will be dry today, but will have to keep an eye on lake enhanced snow showers streaming south near the IL/IN border today. Kept low PoPs or flurries in the forecast for Vermilion County to account for this potential.

Into Sat night, the sfc high shifts to the ArkLaTex region, with the ridge axis extending northeast through IL. The combo of weak winds and clear skies will allow lows to drop near zero across much of the ILX CWA, with wind chills as cold as 0 to 10 below Sun AM. This isn't particularly noteworthy, as we've had several recent mornings with colder values, however, I wanted to mention it since this is the last time in the current forecast period (through next Saturday) that the wind chills are forecast to fall below zero.

*** SUNDAY ***

A weak clipper is still on track to reach the region Sun PM, with light snow expected. As is often the case in high PoPs, low QPF scenarios, the model blend is delivering PoPs that are too low for the situation. Forecast soundings across a variety of models show saturation from the sfc into the mid-level, which will be sufficient for snow given modest DPVA (synoptic scale ascent). The saturated layer is generally warmer than the dendritic growth zone, so am not anticipating overly efficient snow production. Coordinated with surrounding offices to boost PoPs into the 30-40% range (mainly north of I-72) Sunday afternoon and evening, and would not be surprised if they are raised further as we get closer to the event. A few tenths of snow accumulation is possible, and could result on slick road surfaces, especially on those that are untreated. The probability of over 1" of snow is less than 10%.

Fcst soundings suggest we lose saturation from the top-down as this event concludes, which given the temperature profile leaves some concern that a loss of cloud ice could lead to a brief period of freezing drizzle Sun eve. It's always a challenge to pin down whether or not precip shuts off before the potential loss of cloud ice occurs. For now, this is just something to monitor, did not add any mention of freezing drizzle to the grids Sun PM.

*** NEXT WEEK ***

Through much of next week, the synoptic pattern will generally continue to feature ridging over the western US and troughing over the eastern US/Great Lakes. The main weather highlights include some moderation of the temps, with highs typically falling somewhere between the mid 20s and mid 30s each day, and precip potential on Tues and Fri.

Guidance has trended weaker and further south with the Tues system, which has taken a lot of the higher impact scenarios for central IL off the table. Still need to monitor the p-type closely, as the low- level thermals will be near zero at times, and it doesn't take much ice to cause issues, but for now deterministic forecast soundings for our CWA seem to favor snow as the primary p-type. This trend is corroborated by the latest NBM ProbIce fields, which have shifted the corridor of icing potential (10-15% chance of 0.01") south of the ILX CWA (previously, the 10-15% chance was focused right across our area). QPF amounts for the ILX CWA also trended lower, so despite the expectation of mainly snow, significant accumulations appear unlikely. The latest probabilistic NBM has just a 15-20% chance of 1" of snow through Wed AM, and less than a 5% chance of 4" of snow.

Late in the week, a clipper system is still progged to swing through the Great Lakes. Based on the current track of this system, precip chances increase as you go north from the ILX CWA, from 20% along the I-74 corridor to 40% along a Rockford to Chicago line.

Erwin

AVIATION

(For the 12z TAFs through 12z Sunday Morning) Issued at 446 AM CST Sat Jan 31 2026

Light flurries are possible at the I-74 terminals this morning, with ceilings of 3500-5000 feet associated with the light snow. Visibility reductions appear unlikely. Northwesterly winds persist through the day, around 10-12 knots, then winds weaken after sunset and turn to westerly for a few hours before becoming light and variable overnight. Lake-effect snow is possible near the IL/IN border through the day today. While the precipitation should stay east of KCMI, ceilings may drop to MVFR at times during the late afternoon/early evening.

Erwin

ILX WATCHES/WARNINGS/ADVISORIES

None.