textproduct: Central Illinois

KEY MESSAGES

- Light snow will progress from west to east this afternoon and evening. Accumulations are unlikely to exceed one inch, but the snow could result in untreated roadways becoming slick.

- Temperatures moderate a bit this week, with highs ranging from the mid 20s to mid 30s Monday through Wednesday, then low 30s to low 40s on Thursday and Friday.

- There is another chance (20-30%) for snow on Tuesday, mainly south of I-72.

DISCUSSION

Issued at 144 AM CST Sun Feb 1 2026

*** THROUGH TONIGHT ***

Another cold morning across central IL to start February, with temps in the single digits in many locations. The exception is east of a Bloomington-to-Effingham line, where a persistent stream of cloud cover off Lake Michigan has helped keep temps in the teens as of 06z/midnight Sun. More recent satellite imagery from around 07z/1am shows considerable erosion of the cloud deck, so temps may still drop into the single digits across eastern IL before daybreak.

Our next disturbance comes in the form of a shortwave over the Dakotas/MN which will dig southeast today. Light snow was ongoing over portions of MN, eastern Dakotas, and eastern NE (as of 07z/1am). Visibility within this snow is generally being reported as 2-4 miles, with localized areas where the vis is down to 1-2 miles. Much of the forecast remains on track for today, with this wave expected to spread snow into the ILX CWA from NW to SE, beginning late morning or around midday. It will be a slow eastward progression, such that snow may not start along the I-57 corridor until after 00z/6pm today. Snow could linger into Sun night, especially near I-57, but precip should depart the area before the Monday AM commute. The prob of snow exceeding a half inch is just 10- 20%, per the latest HREF (adjusted for an SLR closer to 15:1). Given how cold we've been, snow will accumulate on all surfaces, and could result in slick spots on untreated roadways.

With ample cloud cover through the night, lows are forecast to be warmer than previous nights, with lows in the teens and wind chill values hovering near or just above 10 degrees above zero.

*** REST OF THE WEEK ***

No major shifts were noted in the extended forecast with the 00z guidance suite. Additional disturbances will offer precip chances on Tues and Thurs night-Fri, with the Tues sfc low tracking through the TN Valley and the late week low being a clipper system that swings through the Upper Midwest.

Since there were no notable changes to the sfc low track on Tues, the expectation remains that snow is the probable precipitation time within the ILX CWA, and that the PoPs will mainly be focused south of the I-72 corridor/Vermilion Co. The latest model blend has just a 20-30% chance of any snow south of I-72/Vermilion Co. on Tues, with just a 10-15% chance of 1" of snow east of a Paris to Effingham line (near zero to the west). The chances of accumulating snow increase as you shift east of the ILX CWA.

There is strong ensemble agreement (small spread) in the temperature forecast through Thurs. Highs oscillate between the mid 20s and mid 30s through Wed, then could approach 40 on Thurs- Fri as southwesterly flow ramps up ahead of the late week clipper passing to our north. While any warmup is welcome at this point in the winter, it's worth noting that breezy winds both Thurs-Fri will make it a struggle for wind chills to climb above freezing either day. In between the Tues system and the late week clipper, a modest sfc high (around 1030 mb) settles in to the Midwest, which could result in some cold nights, particularly Wed night into Thurs as cloud cover diminishes. The latest forecast has lows in the single digits east of I-55.

The ensemble spread in the temperature forecast increases considerably beyond Fri, with a 15 to 20 degree gap between the 25th and 75th percentile (meaning there is just a 50% chance that temperatures fall within that given 15-20 degree range). That spread makes it very difficult to put stock in any deterministic forecast value for Sat onward.

Erwin

AVIATION

(For the 06z TAFs through 06z Sunday Night) Issued at 1034 PM CST Sat Jan 31 2026

Still seeing a stream of MVFR level clouds coming off Lake Michigan, extending as far west as a KORD-KDEC line. Ensemble guidance suggests this will persist at KCMI through about 10-11z, whereas KDEC will be in and out for a few hours.

Focus later in the TAF period shifts to an incoming system, which will bring lowering ceilings/visibilities and some light snow late Sunday afternoon into evening. By 00z, probabilities of ceilings below 3000 feet are up to about 60-70% from KPIA-KSPI, and quickly increasing early evening further east.

Geelhart

ILX WATCHES/WARNINGS/ADVISORIES

None.