textproduct: Central Illinois

KEY MESSAGES

- By early evening, snow showers will be possible (20-40% chance) and could produce sharp visibility reductions and slick spots on roadways during the evening commute as temperature plummet behind the front.

- Wind gusts could approach 45 mph at times this afternoon and evening. Gusts will be out of the south ahead of the front, then west-northwest behind the front. A Wind Advisory is in effect for central and southeastern Illinois.

- Temperatures fluctuate through the weekend, with the coldest conditions Friday morning as wind chill values fall below zero north of I-70. Well above normal temperatures are forecast for next week.

DISCUSSION

Issued at 156 PM CST Thu Dec 18 2025

The high for today has already occurred this morning ahead of the cold frontal passage. Temperatures will continue to plummet as the front progresses east. As of 20z (2pm), the front is now east of a Champaign to Effingham line. Winds ahead of the front are out of the south and quite strong, with gusts from 40-50 mph. Winds behind the front are out of the northwest and much more relaxed at the moment compared to ahead of it. The northwesterly winds are expected to get gusty again as a secondary boundary moves through, primarily in areas west of I-55. NBM probabilities show a 20-40% chance of wind gusts exceeding 40 mph later this evening. The Wind Advisory is in effect now and will expire at midnight, but could be cancelled earlier if the winds settle down below advisory level sooner.

Behind the front, we will see some wintry mix then snow showers as the CAA dramatically drops the temperatures below freezing. Overall, amounts from the snow showers should remain minimal, around maybe a tenth or two. However, there is a signal for the potential of snow squall development or banding. There is a decent area of FGEN around 00z-03z based off the models, with 30-50 J/kg of instability (SBCAPE) co-located. Timing for development is from 00z to 03z Friday (6pm-9pm Thursday). With any snow squall or stronger band that develops, rapidly deteriorating road conditions and limited visibility is possible. When heading out for the evening, stay aware of the weather and its impacts. Roads could become slippery and icy as temperatures drop below freezing.

Dry weather will settle in for the weekend by early tomorrow morning. Highs will bounce around this weekend before leveling out by mid-week. Tomorrow's highs will be in the upper 20s to mid 30s, with lows in the teens that morning. Wind chills in the morning will be bitter with values near and below zero. Saturday will warm up into the mid 40s to low 50s, with lows in the 20s. Sunday will drop back into the low 30s to near 40, with lows in the 20s. Temperatures will get well above normal with values as high as the mid 60s by Christmas.

Copple

AVIATION

(For the 06z TAFs through 06z Friday Night) Issued at 1027 PM CST Thu Dec 18 2025

Wrap-around moisture on the back side of a departing storm system is resulting in broken MVFR ceilings tonight. This trend will persist through about 12z, by which time skies will begin clearing from west to east.

Gusty west winds will continue through the overnight hours, too, diminishing Friday afternoon once high pressure builds across the region. Then, winds will shift south and increase again by Friday evening ahead of the next frontal system.

MJA

ILX WATCHES/WARNINGS/ADVISORIES

Wind Advisory until midnight CST tonight for ILZ027>031-036>038- 040>057-061>063-066>068-071>073.