textproduct: Central Illinois

KEY MESSAGES

- After a dry and seasonably cool weekend, temperatures will average 10 to 15 degrees above normal next work week.

- The highest (40-60%) chance for appreciable rain in the next 7 days will be Thursday into Friday.

DISCUSSION

Issued at 1259 AM CST Fri Jan 2 2026

***** COOL AND DRY THIS WEEKEND *****

Early Friday morning, 500mb northwest flow was over central/southeast IL between a large trough over the Hudson Bay and a smaller shortwave trough across the southern High Plains. At the surface, high pressure is maintaining dry conditions and light winds. The southern stream disturbance and another developing further upstream will both pass through the lower-mid Mississippi Valley into the Tennessee Valley this afternoon, bringing increasing mid-high clouds which will limit radiational warming and result in another day of seasonably cool temperatures with highs in the low- mid 30s area-wide. In the wake of those features tomorrow, HREF guidance suggests clouds will likely (70-90% chance) leave our area giving us sunshine, though cool northerly flow will keep our temperatures from climbing out of the 30s yet again.

***** WARM NEXT WORK WEEK *****

The surface high will finally shift east Sunday night, allowing southerly return flow to overspread the Prairie State to kick off the work week. Consequently, temperatures are forecast to climb into the upper 40s to low 50s by Monday afternoon, and 50s area-wide (80% chance, per NBM) on Tuesday. Ensemble guidance generally suggests 500mb heights will remain above normal to maintain seasonably warm temperatures (40s and 50s) through Thursday or Friday, though apparent in the global deterministic models are a few shortwave disturbances which will result in subtle daily temperature variations and varying degrees of cloudiness. There's no clear signal for precipitation, however, until late in the week when the upper level height pattern becomes increasingly amplified as ridging builds over the east and a trough dips into the Intermountain West. Any disturbances lifting northeast through the deep southwest flow over the nation's midsection could tap into sufficient Gulf Moisture to give our neck of the woods a beneficial rainfall, though precise system track will be key; at this time, NBM gives the entire area a 30-50% chance for more than a half inch of rain.

Bumgardner

AVIATION

(For the 12z TAFs through 12z Saturday Morning) Issued at 532 AM CST Fri Jan 2 2026

Two waves of MVFR ceilings are drifting southward across central IL this morning: the first is exiting DEC and SPI, while the second is drifting southward into PIA and BMI. It remains to be seen whether this second wave will make it south to impact the other airfields, but with GLAMP advertising its arrival at SPI and DEC mid morning opted to add a tempo group there from 14-17z (8-11am). Otherwise, expect predominantly VFR conditions and gentle north-northeasterly breezes throughout the forecast period.

Bumgardner

ILX WATCHES/WARNINGS/ADVISORIES

None.