textproduct: Central Illinois

KEY MESSAGES

- The first snow flakes of the season are on tap for locations along and northeast of a Bloomington to Mattoon line late tonight into Friday morning as bands of light rain/snow showers from Lake Michigan arrive from the northeast.

- Below normal temperatures will prevail through the upcoming weekend before a gradual warming trend gets underway next week.

DISCUSSION

Issued at 401 AM CST Thu Nov 12 2026

**** Blustery Conditions Today ****

09z/3am satellite imagery shows partial clearing across central Illinois: however, ample cloud cover is noted upstream across Wisconsin/Minnesota thanks to a short-wave trough dropping through the Upper Midwest. Clouds will increase as this feature nears...and enough synoptic lift will be generated to warrant slight chance PoPs (20%) for light showers/sprinkles. Given mostly cloudy skies and strong CAA courtesy of NW winds gusting 25-30mph, temperatures will struggle to rise today. Afternoon highs will range from the lower 40s far north around Galesburg and Lacon to the lower 50s south of I-70. Meanwhile the wind will make it feel like its in the 30s.

**** First Snow Flakes of the Season ****

Once the short-wave trough drops into the Ohio River Valley, synoptic subsidence on its backside will lead to partial clearing and dry conditions across much of the KILX CWA tonight. The exception will be locations along/northeast of a Monticello to Paris line where very light lake-enhanced precip may arrive. With a fetch of very cold air characterized by 850mb temperatures of -6 to -7C flowing over the warm waters of southern Lake Michigan that are currently around 55F (13C), the stage will be set for a persistent band of lake-effect precipitation. 00z and 06z Nov 12 CAMs have shifted the band further west than previous runs...with the HRRR and RRFS focusing the most persistent banding along the Illinois/Indiana line from near Gary, Indiana southward to near Watseka. Forecast soundings are initially warm enough to support rain showers during the evening, but cool sufficiently for a change over to snow showers late tonight into Friday morning. Some of this very light rain/snow may drop as far south as a Monticello to Paris line overnight. As another subtle short-wave drops southward through the Great Lakes, the fetch over the lake will become a bit more N/NE for a time Friday morning. This will likely shift the band even further west, with some solutions suggesting snow flakes as far southwest as a Bloomington...to Decatur...to Mattoon line. With just very light snow expected and ground temperatures still warm, only trace amounts of snow accumulation on grassy surfaces are possible across the far NE KILX CWA. Further north where the snow will be more persistent, accumulations become more likely...with the 00z REFS indicating a 10-15% chance for greater than 0.5" along/north of a Rantoul to Hoopeston line.

**** Cold Weekend Then Warmer Next Week ****

The lake-effect band will shift NE and gradually dissipate late Friday as high pressure builds into the region from the west. Given clearing skies and winds becoming nearly calm, a chilly weekend is in store with daytime highs in the 40s and overnight lows in the 20s. After that, the deep upper trough east of the Mississippi River will retreat into eastern Canada and heights will climb markedly next week. High temperatures will moderate to near seasonal values in the lower to middle 50s on Monday/Tuesday...then will climb back above normal into the 60s by the middle and end of next week.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

Issued at 450 AM CST Thu Nov 12 2026

A band of clouds associated with an upper disturbance will drop southward through central Illinois this morning. Upstream obs show mainly low VFR ceilings with a few pockets of MVFR and the HRRR/RRFS both suggest only scattered MVFR as the band arrives. Have opted to go with the lower side of guidance and carry a period of MVFR with VCSH accordingly. Once the band passes, VFR ceilings will prevail for the rest of the 12z TAF period. Will need to keep a close eye on an expected band of lake-effect precip flowing off Lake Michigan tonight into Friday morning. While the bulk of the precip will remain just N/NE of central Illinois, think it may come close enough to KCMI to cause ceilings to potentially lower to MVFR in light snow overnight. Given the uncertainty of the exact W/SW extent of any precip, have kept conditions VFR at this time. Winds will be NW with gusts of 20-25kt today, then will decrease to 10-15kt tonight.

ILX WATCHES/WARNINGS/ADVISORIES

None.