textproduct: Central Illinois

KEY MESSAGES

- Light snow (60-80% chance) this afternoon and evening will result in slick spots on roadways. Allow extra time to reach your destination and take it slow on the way.

- There is a 20-30% chance for accumulating snow southeast of a Shelbyville to Paris line on Tuesday. Flurries may occur Monday night into Tuesday morning further north, but accumulations there should be minimal.

- Temperatures will be less cold this work week, with highs generally in the 20s and 30s Monday through Thursday.

UPDATE

Issued at 717 PM CST Sun Feb 1 2026

Water vapor imagery this hour shows the defined curl associated with the upper trough now centered just northwest of Bloomington. Some heavier snow showers associated with this curl have been tracking along the I-74 corridor, with a broader area of light snow extending from Havana southeast to near Vandalia. Webcams and traffic are not showing many impacts so far, with mainly a thin coating of snow on surfaces that do not already have a heavy concentration of residual snow/ice treatment. Evening sounding from our office still shows a decent dry layer below 850 mb, which appears to be keeping things in check.

Upstream, the surface boundary is pushing southeast across central Iowa. Surface reports have been indicating some light freezing drizzle in that area. HRRR forecast soundings do show we begin to lose ice crystals in the column after 9-10 pm, so potential for light icing this far south will need to be watched closely.

Geelhart

DISCUSSION

Issued at 1255 PM CST Sun Feb 1 2026

***** LIGHT SNOW THIS EVENING *****

At 1pm Sunday, temperatures were in the upper teens to low 20s across central and southeast IL. Surface high pressure was shifting eastward into the Ohio Valley, allowing for south-southwest winds across the region. Meanwhile, a shortwave trough was diving southeast into the area to bring widespread clouds and an area of light snow. Though taking time to erode the dry air in place (PWAT on our 12z raob was 0.12"), snow should spread east of the IL River to overtake most of central/southeast IL over the next few hours. Accumulations will be light with this activity, with most locations seeing between a dusting and an inch - enough to cause some slick patches on roadways.

***** LESS COLD TOMORROW *****

After so many nights with lows in the single digits above/below 0, cloud cover and lingering flurries tonight will limit radiational losses favoring a milder night with lows in the upper teens. While some of those clouds will hang on tomorrow (mainly east of I-55), ridging quick to expand back into the area on the heels of today's shortwave trough will favor a warmer day with highs likely (60-80% chance, per NBM and REFS) reaching the 30s - warmest in west-central IL. This will be the first time many locations break 30 degrees since January 22nd.

***** SNOW IN SOUTHEAST IL TUESDAY? *****

Another trough will flatten the ridge tomorrow evening into Tuesday, with a surface low passing across the TN/OH Valleys on Tuesday. While that will be the feature to watch for accumulating snow in areas mainly south of a Shelbyville to Paris line on Tuesday, small vort maxes further north could provide sufficient lift for a few flurries across the rest of central IL as early as tomorrow night. With the NAM/GFS suggesting a brief period of negative saturated EPV atop a band of modest FGEN in the 650-500mb layer (indicative of CSI), and time heights likewise showing a "crosshair" signature (vertical motion max and RH > 90% in the DGZ) on Tuesday, we suspect a quick 1-3 inches of snow will accumulate in a narrow band. The question is where, and that remains to be seen. At this time, the highest chances (20-40%) for seeing more than an inch of snow from NBM/LREF are outside our area in southern IN/northern KY, though areas south of I-70 in southeast IL still stand around a 20% chance.

***** SEASONABLE TEMPERATURES MID-LATE WEEK *****

Dry conditions should return Tuesday night as surface high pressure settles back into the region. Depending on cloud cover, Tuesday and especially Wednesday nights could feature some single digit lows, with NBM giving the highest chances (50-70%) in eastern IL Wednesday night. As the surface high shifts east, warm advection will return on Thursday to usher milder temperatures back into the region, though with southwest winds gusting to 30 mph it won't exactly feel warm. It remains unclear precisely when the shortwave trough and attendant surface low will swing through the local area, and also how far west the cold air spills, which is resulting in low confidence in forecast temperatures Thursday night through Saturday. The deterministic models and their respective ensembles have generally trended further east with the push of arctic air, with the LREF mean now confining sub -20 degC 850mb temps to Upstate NY. Our area looks to receive a glancing blow, with temperatures moderating as ridging expands back into the region early next week (of 2/8), though it's worth noting a subset (~20%) of LREF hold onto near/below normal 500mb heights through Monday, 2/9. The highest chance (40-60%) for high temperatures over 40 degF in this forecast package (through Saturday, 2/7) is west of I-55 on Friday.

Bumgardner

AVIATION

(For the 06z TAFs through 06z Monday Night) Issued at 1033 PM CST Sun Feb 1 2026

MVFR conditions thus far have been more associated with passing light snow, but a larger area of sub-3000 foot ceilings is advancing southeast toward the Illinois River. All TAF sites should have about a 4-6 hour period of MVFR ceilings, before a surface boundary shifts winds to the northwest and clouds begin to scatter out. KCMI may take much of the morning to see conditions improve, as ensemble guidance keeps MVFR probabilities up to 50-70% as late as 17z.

Geelhart

ILX WATCHES/WARNINGS/ADVISORIES

None.