textproduct: Central Illinois

KEY MESSAGES

- Strong south winds will develop Tuesday, with a 50 to 70 percent chance of wind gusts exceeding 40 mph across central Illinois.

- Widespread rain arrives Tuesday into Wednesday, averaging around 1 inch across the region with a 10 percent chance of localized amounts reaching up to 2 inches.

DISCUSSION

Issued at 146 PM CST Sun Nov 1 2026

NEAR TERM /THIS EVENING THROUGH MONDAY/... A shortwave trough embedded within broader upper-level ridging continues to push across central Illinois this afternoon, generating scattered showers. As this wave shifts east into Indiana by late this afternoon and early evening, precipitation coverage will diminish in its wake. However, mid-level warm air advection (WAA) will intensify this evening and overnight in response to a deep upper trough digging over the Intermountain West and driving cyclogenesis over the Front Range of the Rockies. Weak isentropic ascent atop a shallow moist layer of low stratus may squeeze out patchy drizzle overnight into Monday morning.

SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/... A pair of potent mid-level shortwaves--one situated over the Four Corners region and another over northern Saskatchewan early Monday morning--will drive renewed precipitation chances through the first half of the work week. Model guidance has converged into better agreement regarding the evolution and degree of phasing of these waves through at least Thursday. A slow-moving surface low will lift from eastern Colorado early Monday into the Upper Midwest Tuesday into Wednesday.

Synoptic forcing remains somewhat mixed on Monday as central Illinois sits squarely beneath the upper-level ridge axis with neutral mid-level height tendencies offset by continued low- level WAA. This may prove sufficient for isolated light rain or drizzle through the day Monday, though QPF will be minimal. NBM mean 24-hour QPF remains under 0.10 inches Monday through Monday night, with many dry hours anticipated throughout the day.

As the surface low occludes and meanders over the Upper Midwest Tuesday into Wednesday, an attendant cold front will approach and cross central Illinois. A tightening southerly pressure gradient will yield strong, gusty winds on Tuesday. NBM probabilities for wind gusts exceeding 40 mph range from 50-70% across a significant portion of the CWA. Thermal advection ahead of the boundary will push high temperatures into the 70s Tuesday afternoon. Breezy conditions persist into Wednesday, easing slightly as the frontal trough approaches, with probabilities for gusts exceeding 30 mph hovering around 50%.

Concurrently, a solid band of showers with embedded thunder will sweep across the region Tuesday into Wednesday. NBM 48-hour mean QPF through Wednesday night is approximately 1.00 inch area-wide, while 90th percentile ensemble guidance indicates localized totals up to 2.00 inches. Instability remains a primary limiting factor for severe potential; GFS soundings reveal meager pockets around 50 J/kg MUCAPE, keeping overall severe risk low along the front.

LONG TERM /THURSDAY THROUGH SUNDAY/... Frontal passage will signal an end to widespread precipitation late in the week as the surface low gradually fills and tracks east across the Great Lakes. Lingering low-level cyclonic flow and wrap-around moisture within post-frontal CAA will maintain stratocumulus clouds along with isolated sprinkles or light showers Thursday and Friday. Highs late week will cool into the 50s in spots. GFS and ECMWF suggest another fast-moving shortwave may clip the region over the weekend, though details remain uncertain. NBM currently maintains a baseline 15-20% PoP for Sunday.

AVIATION /18Z TAFS THROUGH 18Z MONDAY/

Issued at 1113 AM CST Sun Nov 1 2026

Low pressure will develop and lift across the Great PLains through Monday. A modest southeast breeze around 10 kt will prevail much of the period across central Illinois. Ceilings will lower from the south late this afternoon through the evening with conditions eventually dropping to IFR overnight through Monday morning. Occasional light showers or patchy drizzle will be possible at times, with the latter most likely Monday morning accompanying the IFR ceilings.

ILX WATCHES/WARNINGS/ADVISORIES

None.