textproduct: Central Illinois

KEY MESSAGES

- Scattered showers and a few thunderstorms could bring localized rainfall up to 0.5 inches today, primarily west of Interstate 55 before shifting north tonight.

- Temperatures near 70 degrees on Saturday will cap off one of the warmest Octobers on record.

- A stronger storm system brings widespread rain and breezy conditions Monday afternoon through Wednesday morning. There is a 50-60% chance for rainfall totals to exceed 1 inch during this timeframe, especially along and west of Interstate 55.

DISCUSSION

Issued at 325 AM CDT Fri Oct 30 2026

A weak baroclinic zone extends from near Des Moines, Iowa, to Cincinnati, Ohio, early this morning. Scattered showers and thunderstorms are ongoing along this boundary, concentrated primarily near the nose of a 20-30 kt low-level jet. To the north, downwind of the mid-level trough axis, a surface high pressure ridge stretches across the Northern Plains, Great Lakes, and Ohio Valley. Persistent low-level dry air over the Great Lakes and easterly winds across central Illinois today create uncertainty regarding how far east precipitation will push. The highest probability for rain (60%) remains west of Interstate 55 during the day, with chances shifting northward by this evening. Forecast rainfall totals through this evening are generally less than 0.25 inches along and west of I-55, though localized amounts up to 0.5 inches are possible across far west- central Illinois where low-level jet forcing is stronger this morning. Precipitation chances (30-50%) remain focused near and north of the I-74 corridor tonight through Saturday morning. Low-level jet forcing will serve as the primary catalyst for any shower activity that develops.

Precipitation chances taper off by Saturday afternoon and evening (10-30%) as low-level dry air filters into the area from the southeast. Despite abundant clouds, temperatures should once again warm to around 70 degrees areawide, capping what will be one of the warmest Octobers on record.

Rainfall chances return by Sunday morning as a shortwave trough advances out of the Southern Plains into the Mid-Mississippi Valley. Warm-air advection accompanying this system brings a medium (40-60%) probability of rain, primarily near and south of the Interstate 72 corridor. However, recent QPF guidance indicates rainfall totals will remain under 0.25 inches, offering minimal relief to ongoing dry conditions.

The highest confidence for rainfall over the coming 7 days spans Monday afternoon through Wednesday morning. During this period, global models indicate the jet stream will buckle over the central U.S., driving several mid-level shortwave troughs southward across the region. While exact phasing details among these troughs remain uncertain, deterministic and ensemble guidance strongly agree on a large-scale storm system delivering periods of widespread rain, breezy conditions, and cooler temperatures. Additionally, recent NBM guidance indicates a 50-60% chance of rainfall exceeding 1 inch over the 48-hour period ending at 6 AM Wednesday, particularly for locations along and west of Interstate 55.

Following the departure of the storm system, a continental polar (cP) air mass will settle across the area, favoring dry and mild weather through the latter portion of next week. Expect cooler conditions, with daily high temperatures around 60 degrees and overnight lows falling into the upper 30s to lower 40s.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1208 PM CDT Fri Oct 30 2026

A stationary front is expected to remain just south of the terminals with a modest easterly breeze and isolated to scattered showers across central Illinois. VFR conditions should prevail through the period, but cannot rule out brief MVFR ceilings or vsby in or around showers. The thunder threat is low, but non-zero. As we head into the evening and overnight hours, the focus for precip is expected to shift slightly northward favoring PIA/BMI.

ILX WATCHES/WARNINGS/ADVISORIES

None.