textproduct: Central Illinois

KEY MESSAGES

* Isolated to scattered (20-40%) showers will continue through Sunday afternoon. Rainfall under a tenth of an inch is most likely with isolated pockets around a quarter inch.

* Gusty winds arrive Tuesday with a 40-60% chance for wind gusts to exceed 40 mph.

DISCUSSION

Issued at 158 PM CDT Sat Oct 31 2026

This Weekend... Surface high pressure remains centered over the lower Great Lakes this afternoon, while aloft, an expansive ridge stretches from the Southeast CONUS to the Canadian Rockies. Meanwhile, a deep upper low is positioned off the Pacific Northwest coast. Water vapor imagery shows a series of shortwave troughs buckling the upper ridge as they lift towards and across the mid- Mississippi Valley. Isolated to widely scattered showers will persist across central Illinois ahead of the first wave this afternoon and evening, lifting into northern Illinois tonight. A second wave will bring another round of showers primarily south of I-72 late tonight.

Weak low-level lapse rates and dry air below 700 mb may yield more virga than measurable rainfall today and tonight. HREF mean 24-hour QPF averages under 0.10 inches through Sunday morning, though LPMM guidance indicates isolated swaths up to 0.25 inches are possible within heavier showers. Weak instability (<100 J/kg) and low equilibrium levels preclude thunder mentions through tonight. Lingering showers Sunday morning will remain light, tapering off from the west by Sunday afternoon as the trailing shortwave clears and upper ridging rebuilds. Despite cloud cover and light rain, temperatures remain above normal with highs in the 60s, reaching the lower 70s south of I-70.

Early Next Week... A pair of potent mid-level shortwaves/closed H5 lows will dig into the western CONUS early next week--one tracking across the Intermountain West and another across the Canadian Rockies. Model guidance continues to exhibit spread regarding the interaction and phasing of these waves, leading to variance in surface patterns for the mid-to-late week period. Nevertheless, broad mid-level height falls over the Rockies will induce surface cyclogenesis over eastern Colorado early in the week.

The surface low is forecast to deepen as it lifts into the Upper Midwest Tuesday, though model disparity increases regarding system track and intensity. Stronger solutions favor breezy to windy conditions across central Illinois on Tuesday; NBM probabilities for wind gusts exceeding 40 mph range from 40-60% across a good portion of the area. Warm advection ahead of the system will push highs into the mid 70s Tuesday afternoon.

Late Next Week... A cold front associated with the elongated surface trough will cross central Illinois in the Wednesday to Thursday timeframe, with timing trending slightly faster in recent model suites. Temperatures well into the 60s ahead of the boundary will fall back into the 50s post-frontal. The frontal passage will signal the end of widespread precipitation, though lingering low-level cyclonic flow and cold air advection may maintain stratocumulus cover along with a few light sprinkles into late week.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 1221 PM CDT Sat Oct 31 2026

A series of upper level disturbances will bring periodic chances for showers to central Illinois. Precip will favor areas near the Illinois River Valley this afternoon and evening. The next round of rain will spread into areas southeast of the Illinois River Sunday morning. East to southeast winds will prevail through the period, though slightly lower magnitudes overnight may allow for some variability in wind direction. VFR conditions prevail outside of precip today and tonight, but MVFR and possibly IFR ceilings lift north into the region Sunday morning.

ILX WATCHES/WARNINGS/ADVISORIES

None.