Area Forecast Discussion

KEY MESSAGES

- Scattered showers push north today, followed by intermittent rain chances through Monday with modest rainfall amounts.

- A strong, dynamic storm system midweek brings widespread heavy rainfall and gusty winds.

- Dry and seasonable conditions return for late next week following the cold frontal passage.

DISCUSSION

Issued at 354 AM CDT Sat Oct 31 2026

Near Term (Today through Sunday)

Morning radar imagery depicts a focused precipitation band continuing to lift north of the I-74 corridor as supporting thermal advection and isentropic ascent weaken and shift northward. A temporary lull in rainfall is expected through midday. By this afternoon, a negatively-tilted shortwave trough emerging from the Missouri Valley will provide synoptic-scale forcing for renewed shower activity through early evening. However, inconsistent moisture profiles will limit overall coverage and QPF. Although select CAM guidance indicates MUCAPE reaching a couple hundred J/kg, weak lapse rates will dampen convection, keeping thunder chances low.

Intermittent rain chances persist Sunday into Monday as warm- air advection and isentropic lift strengthen ahead of additional shortwave impulses crossing the region. Moisture availability remains a limiting factor, constraining broad coverage. NBM Mean 48-hour QPF indicates widespread 0.10 to 0.25 inches east of the Illinois River Valley through 6 PM Monday, though 90th percentile guidance highlights localized amounts of 0.50 to 0.75 inches.

Dynamic Midweek Storm System (Monday Night through Wednesday)

Forecast uncertainty increases by Monday night as the jet stream buckles over the central U.S., driving multiple mid- level shortwave troughs southward through midweek. Minor model discrepancies persist regarding trough phasing and precise frontal timing, though consensus is converging on a Tuesday evening cold frontal passage across central Illinois.

As the synoptic low deepens and upper-level energy consolidates, the surface pressure gradient tightens significantly. EPS and GEFS mean wind gusts project peak gusts of 20-30 mph on Monday, increasing to 30-40 mph on Tuesday in the vicinity of the cold front. This dynamic system will draw a rich plume of Gulf moisture northward, pushing atmospheric precipitable water (PWAT) values near 1.75 inches--approaching the 99th percentile for early November climatology. NBM Mean 48-hour QPF supports widespread rainfall totals around 1.0 inch through 6 AM Thursday, with high-end 90th percentile forecasts indicating localized totals between 2.5 and 3.0 inches.

Extended / Late Week (Thursday and Friday)

In the wake of the exiting storm system, a continental polar (cP) air mass will overspread the region, bringing dry and seasonable weather for the remainder of next week. Expect daily high temperatures near 60 degrees with overnight lows dropping into the upper 30s and lower 40s.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/

Issued at 543 AM CDT Sat Oct 31 2026

VFR conditions to prevail through this TAF period as low-level dry air keeps ceilings in check. Did add a prob30 group for showers between 16z-00z as a disturbance slowly lifts across the regional terminals. Otherwise, dry conditions and a persistent east wind will remain.

ILX WATCHES / WARNINGS / ADVISORIES

None.