textproduct: Central Illinois

KEY MESSAGES

- A period of snow is likely Saturday morning west of I-55, followed by scattered gusty snow showers late Saturday afternoon and evening.

- Temperatures trend significantly warmer Monday and Tuesday before a cold front returns the region to more seasonable conditions mid to late next week.

DISCUSSION

Issued at 116 PM CST Fri Jan 9 2026

Northwest winds will continue to diminish this afternoon as a ridge axis builds in from the west. This evening, cloud cover increases again ahead of a shortwave currently tracking northeast through the OK panhandle.

Late tonight into Saturday morning: a somewhat complex precipitation event is on track. 12z deterministic guidance indicates a period of intense mid- level lift associated with the shortwave arriving after 09z, initially spreading in rain or a rain/snow mix west of I-55. Soundings indicate a column near freezing, where dynamic cooling in the stronger band of lift will likely drive a transitory burst of moderate wet snow west of the I-55 corridor (most likely near and west of the IL River). If snowfall rates are high enough, this could overcome marginal surface/ground temperatures, resulting in a quick dusting to 1" of wet snow accumulation, primarily on grassy and elevated surfaces. 12z HREF shows a 40-80% chance of measurable snow (>0.1") north of a Rushville to Bloomington line, and probabilities > 1" of snow 20-40% northwest of the IL River. Southeast of I-55, precipitation will likely remain rain or a brief rain/snow mix before ending by late morning.

Saturday afternoon and evening: cold advection increases behind the departing wave. Steep low-level lapse rates reaching 8-9 C/km in the 0-2km layer, and resulting weak surface based instability will promote convective snow showers. These snow showers would be capable of laying down a quick dusting to half inch of snow in isolated locations (HREF shows 20-40% chance of measurable). West- northwest wind gusts will increase to 20-30 mph, and higher gusts within snow showers are possible. This will result in briefly reduced visibility and as temperatures fall through the 30s.

Sunday and Monday: High pressure settles to the south, leading to a period of quiet weather. Winds will veer to the southwest by Sunday night, initiating a warming trend. Highs Sunday stay in the 30s, but reach the low-to-mid 40s by Monday.

Tuesday and Wednesday: Significant model variance remains regarding the Tuesday/Wednesday system. The GFS remains the progressive outlier, sweeping a dry cold front through the Midwest, while the ECMWF and ECMWF-AI suggest a slower, deeper trough with an attendant surface low that brings higher precipitation probabilities. Given the ensemble spread, the NBM solution maintains low chance PoPs, primarily for rain, late Tuesday then ending as a rain/snow mix Wed. There is good confidence temperatures will reach well above normal ahead of the system on Tuesday with highs potentially reaching into the 50s for much of the CWA.

Thursday-Friday: Cold air returns behind the midweek front. The ECMWF Extreme Forecast Index (EFI) does not signal any climatologically extreme cold for the end of the week, suggesting a return to near or just below January averages.

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AVIATION

(For the 18z TAFs through 18z Saturday Afternoon) Issued at 1108 AM CST Fri Jan 9 2026

MVFR ceilings have steadily been scattering out from the west this morning. Trends off visible satellite show KDEC will clear around 18z and KCMI shortly after that. Another area of MVFR ceilings has been dropping southeast from eastern IA, and short range guidance shows this could impact KPIA this afternoon so included a TEMPO group for that. Otherwise, MVFR ceilings will redevelop over the region tonight ahead of the next system. As precip overspreads the terminals late tonight, ceilings are forecast to drop to IFR. Included rain/snow mix at the northern terminals (KPIA-KBMI), with a low (30%) potential for a complete changeover to snow at KPIA and IFR visibility. Northwest wind gusts will subside early this afternoon over our eastern terminals with winds going light/variable this evening through much of tonight. After the system moves out mid to late Saturday morning, west- northwest winds will again increase with some gusts to 20+ kt.

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ILX WATCHES/WARNINGS/ADVISORIES

None.