textproduct: Central Illinois

KEY MESSAGES

- A pair of clipper system will pass through northern Illinois tonight and again Wednesday evening. Gusty winds are expected at times and light snow is possible, mainly from I-74 northward.

- An arctic air mass will bring a return of bitterly cold temperatures Thursday night through the weekend. Single digit highs and sub-zero lows will be possible for portions of central Illinois.

- A winter storm system will pass through the southern states Friday through the weekend, and could spread snow into parts of central and southeast IL. There is around a 60 percent chance of exceeding an inch of snow south of I-70 and a 20 percent chance of exceeding 3 inches.

DISCUSSION

Issued at 111 PM CST Tue Jan 20 2026

A large-scale trough remains anchored over the central US, with a subtle shortwave ridge embedded in the base of the trough along with high pressure over the southeast US bringing a respite from the cold air mass as southerly flow develops in the region. This should bring highs in the upper 20s to lower 30s today, followed by mid 30s to lower 40s Wednesday. Lows tonight should fall only to the lower or mid 20s aided by mixing from breezy southwesterly winds. Meanwhile, a couple of clipper-type systems embedded in the northwest flow aloft will move through northern IL, tonight and Wednesday evening, respectively. While these will affect primarily northern IL, light precipitation could extend into parts of central IL, especially north of I-74. Despite some low level dry air, forecast soundings generally indicate this will saturate at least briefly, with lift and saturation through the dendritic growth zone, so have increased PoPs with both features, and have at least a slight chance for much of the forecast area north of I-70. Precipitation type looks to be snow with both, despite the mild highs on Wednesday, as they avoid the warmest part of the afternoon. Amounts look to be light, with most areas seeing only a very light dusting at most, however from around Galesburg to Peoria to Bloomington northward there could reasonably be a significant portion of an inch from the first disturbance (5 percent chance of exceeding an inch).

The next feature of note is an arctic cold front that should arrive Thursday and bring very cold air into the area for Friday through the weekend. Highs should be single digits and teens Friday and Saturday, followed by teens and lower 20s Sunday and Monday. Wind chills as low as 10 to 25 below zero look on track for Friday and Saturday, and maintaining some sub-zero values Sunday and Monday.

A major winter storm will traverse the southern states late this week through the weekend, interacting with anomalously cold air associated with the front that previously traversed central IL. This should bring areas of heavy snow and freezing rain, with at least slight potential for moderate snowfall into parts of central and southeast IL. The storm track remains somewhat variable, however precipitation type at this time appears very likely to be all snow this far north. Probabilities for receiving over a quarter inch of liquid equivalent of precipitation (~ 3+ inches) range from 10 to 30 percent from I-70 southward in southeast IL Saturday morning into Sunday, with very low probabilities (<10%) of receiving such amounts to the north. Ensemble probabilities for under an inch range from around 40 percent south of I-70 to 75 percent north of Peoria suggesting a most likely outcome of light snow for this area.

37

AVIATION

(For the 18z TAFs through 18z Wednesday Afternoon) Issued at 1142 AM CST Tue Jan 20 2026

A clipper type weather system passing through northern IL will bring a chance for light snow tonight, mainly for the I-74 terminals KPIA-KBMI-KCMI and northward, however some brief light snow could extend as far south as KSPI and KDEC. Conditions will be mainly VFR, however a short period of MVFR cigs and vsbys will be possible with snow, again mainly I-74 northward. Winds S-SSW around 10 kts today, becoming SSW 12-16 kts with gusts 20-25 kts overnight, and veering to westerly by the end of the period. Low level wind shear is expected from around 06Z-12Z as SW winds around 45 kts develop at 2000 ft AGL.

37

ILX WATCHES/WARNINGS/ADVISORIES

None.