textproduct: Central Illinois

KEY MESSAGES

- Strong southerly winds will gust 30 to 40 mph at times on Tuesday, with a 30 to 50% chance of reaching advisory criteria (gusts of 45 mph or higher) north of I-70.

- Scattered thunderstorms Tuesday afternoon and evening could produce localized damaging wind gusts, even with little or no lightning.

- Widespread rainfall amounts of 0.75 to 1.50 inches are expected Tuesday through Wednesday night, with a 10% chance of localized totals reaching 2.0 to 2.5 inches.

DISCUSSION

Issued at 1252 PM CST Mon Nov 2 2026

NEAR TERM (TODAY THROUGH TUESDAY)... A pair of potent mid-level shortwaves -- one situated over the Desert Southwest and another over North Dakota -- will drive a slow-moving surface low and cold front across the region through the first half of the week. Surface analysis this afternoon shows a 996 mb low over northeastern South Dakota, with a trough axis extending southwestward into a second low center of 998 mb over western Kansas. Strong southwesterly flow ahead of these synoptic features is fueling robust warm and moist advection across the Midwest.

South-southeast winds gusting 20 to 30 mph today will boost temperatures into the mid 60s today. Highs will warm further into the low to mid 70s Tuesday as the pressure gradient tightens. Southerly wind gusts on Tuesday may approach 40 mph at times, with NBM probabilities for gusts exceeding 40 mph ranging from 50 to 70% across a significant portion of the CWA. The probability of reaching Wind Advisory criteria (45 mph gusts) is roughly 30 to 50% north of I-70. While confidence is currently insufficient to issue a Wind Advisory, a few localized sites may tag criteria. Meanwhile, sustained moisture transport will push surface dewpoints into the low to mid 60s by Tuesday afternoon.

SEVERE WEATHER THREAT (TUESDAY AFTERNOON & EVENING)... As the elongated, double-barrel surface low lifts across the mid and Upper Mississippi Valley Tuesday afternoon, weak instability is forecast to overspread portions of central Illinois. This instability will be superimposed by strong deep- layer shear of 40 to 50 kt, supporting a conditional severe weather threat Tuesday afternoon and evening should localized cloud breaks allow for greater surface heating. Even without robust convective updrafts or lightning, the intense background synoptic flow within the cloud-bearing layer could easily be transferred to the surface, resulting in near-severe or marginally severe wind gusts in convective downdrafts.

HEAVY RAIN & HYDROLOGY (TUESDAY THROUGH WEDNESDAY)... Precipitable water values exceeding 1.50 inches pooling along the frontal zone approach maximum values in the 1985-2012 GEFS reforecast climatology. High rainfall efficiency is expected as a slow-moving band of showers and isolated embedded thunderstorms traverses the forecast area Tuesday into Wednesday. The 48-hour NBM mean QPF through Wednesday night indicates widespread totals of 0.75 to 1.50 inches, with 90th percentile ensemble guidance highlighting localized totals up to 2.0 to 2.5 inches.

EXTENDED PERIOD (THURSDAY THROUGH SUNDAY)... Cold frontal passage will bring an end to widespread moderate- to-heavy precipitation by late Wednesday night as the surface low gradually fills and meanders across the Great Lakes. Persistent low-level cyclonic flow and wrap-around moisture within post-frontal cold air advection (CAA) will maintain cloud cover along with scattered sprinkles or light showers Thursday through Saturday, particularly as shortwave vorticity lobes pinwheel southward around the departing upper trough. Post- frontal high temperatures Friday through the weekend will cool into the 50s, which remains near seasonal normals. Recent GFS and ECMWF guidance is showing better consensus regarding a fast- moving shortwave diving across the region on Sunday, bringing the next opportunity for more widespread light precipitation.

AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/

Issued at 547 PM CST Mon Nov 2 2026

IFR conditions prevail at the central Illinois terminals late this afternoon. Radar/local obs show patchy drizzle and reduced visbys down to 2-3 miles in a few spots...and this should continue for the next couple of hours before the drizzle lifts slowly northward out of the area by mid-evening. While low clouds currently dominate, ceilings improve markedly further south near/south of I-64. All models suggest the continued strong SE boundary layer flow will eventually lift these improved conditions into central Illinois later this evening through the overnight hours. Based on the most recent HRRR/RAP, have improved ceilings to low VFR at KDEC/KCMI by 06z...then further northwest to KPIA by around 10z. A cold will slowly approach from the west on Tuesday, spreading low clouds and showers into the area as the day progresses. Forecast soundings indicate a return to MVFR across the board between 13z and 15z. Showers will primarily impact the western terminals, so have opted to leave rain mention out of KDEC/KCMI through 00z Wed. Winds will initially be SE with gusts of 20-25kt tonight, then will become S with gusts of 25-30kt on Tuesday.

ILX WATCHES/WARNINGS/ADVISORIES

None.