textproduct: Central Illinois

KEY MESSAGES

- While another bitterly cold night is on tap for tonight, some relief is expected Friday through the weekend. Probabilities of temperatures below zero tonight are highest toward the I-72 corridor.

- A series of disturbances will bring precipitation chances every few days through next week. The first one arrives Saturday night, bringing some light snow. There is about a 40-50% chance of more than an inch in areas north of Peoria.

DISCUSSION

Issued at 205 PM CST Thu Dec 4 2025

The forecast over the next several days will be dominated by a series of upper disturbances moving southeast into the central U.S., bringing precipitation chances every few days, and brief respites from the unseasonably cold weather.

The center of Arctic high pressure is drifting across southeast Iowa early this afternoon, gradually suppressing cloud cover in Illinois to areas south of I-70. Lots of temperatures in the mid- upper teens north of I-70, a good 25-30 degrees below normal for early December, but a bit shy of record cold-high temperatures due to today's high temperatures being recorded shortly after midnight. Where the snow cover is thinner south of I-70, low-mid 20s are currently prevailing.

Low temperatures tonight are likely to be in the evening, as the high moves east of the state and winds start to turn more southerly. Latest HREF projects about a 35-40% chance of lows below zero from near Springfield east to Champaign. However, there is some concern that this is being driven too low by high-res models such as the HRRR and the ARW, which bring lows down to as much as 10 below zero. Will go closer to the NBM, which is mainly in the zero to 5 above range north of I-70 and fairly close to the earlier forecast. While a number of record lows will be out of reach, a few are closer to zero for today and Friday (see Climate section below). While wind chills get down to near 10 below near I-74, some slight improvement will be noted overnight as temperatures edge upward. Temperatures moderate somewhat on Friday and Saturday, with much of the forecast area reaching the freezing mark or higher.

Several of the morning models continue to highlight a moist but very shallow layer at the surface beginning this evening. Will continue to highlight potential for freezing fog causing slick spots, especially east of I-55 and north of I-70.

Morning model suite continues to highlight a fast moving storm system crossing the region later this weekend. NBM probabilities of more than an inch of snow are highest north of a Galesburg- Pontiac line (over 50%), ranging to about 20% near I-72/Danville. The GFS ensembles are about 12 hours slower than their European counterparts, and the forecast will continue to focus more on the midnight-noon Sunday period for accumulations.

Additional clipper systems are projected to arrive Tuesday night, then again toward Thursday. The Tuesday night system currently looks to be a more northern track, which would favor more of a rain/snow mix in our area. With the latter system, the deterministic GFS and European models favor a southern track, though a non-trivial number of their ensemble members keep the snow chances more to the north. Plenty of time to watch that, though.

Geelhart

AVIATION

(For the 18z TAFs through 18z Friday Afternoon) Issued at 1105 AM CST Thu Dec 4 2025

Main concern this period is the potential for fog (or low stratus) late this evening and overnight. Guidance suggests the greatest potential for fog is across east-central IL (KCMI, KDEC), but it could expand further west and impact all terminals. Have vis as low as 1 mile at KCMI, KDEC, but confidence in the intensity of the fog is low. With below freezing temperatures, if fog does form and persist it could lead to slick surfaces. Fog development is expected as early as 03-04z, with any fog eroding by 14-15z Fri. Winds will be out of the north this afternoon, becoming variable this evening/overnight, then south-southwesterly Friday.

Erwin

CLIMATE

Issued at 205 PM CST Thu Dec 4 2025

Record low temperatures for today and Friday:

Location Today Friday ======== ======== ========= Bloomington -7 (1893) -2 (1895) Champaign -6 (1893) 0 (1895) Decatur -6 (1893) 2 (1905) Jacksonville 2 (2006) -3 (1895) Lincoln 1 (1929) 3 (2005) Peoria -1 (1991) 0 (2005) Springfield 0 (2006) 4 (1895)

Geelhart

ILX WATCHES/WARNINGS/ADVISORIES

None.