textproduct: Central Illinois

KEY MESSAGES

- An unsettled period of weather is on tap through early next week. While rain chances are in the forecast nearly every day, there will be plenty of dry periods as well.

- The risk for severe weather returns by early next week. NSSL severe weather probabilities increase to 15-30% across central Illinois by Tuesday.

DISCUSSION

Issued at 332 AM CDT Thu Apr 9 2026

08z/2am surface analysis shows a cold front extending from Lake Superior southwestward to near Kansas City. While a couple bands of scattered light showers currently accompany the front, the areal coverage of precipitation has thus far been decidedly underwhelming. Think this trend will continue today as the boundary loses its southward momentum as it becomes parallel to the upper flow. Most CAMs suggest showers across the northern KILX CWA this morning will fade away toward midday, followed by a mostly dry afternoon. High temperatures will be dependent upon where the boundary eventually stalls. Given current position and forward speed, think the front will approach Peoria before it stops. As a result, highs will range from the upper 60s far north around Galesburg to the middle to upper 70s everywhere south of the front.

As a short-wave trough evident on latest water vapor imagery over the Northern Rockies tracks into the Great Lakes, it will give the front renewed southerly momentum and should push it through central Illinois on Friday. As the wave approaches, the NAM depicts a 45-50kt 850mb jet streak developing from the Texas panhandle northeastward to Illinois tonight. This feature will transport additional moisture/instability into the region, with precipitable water values increasing to around 1.25. With better moisture to work with, think showers and a few thunderstorms will become more widespread along/northwest of the I-55 corridor late tonight where 60-90 PoPs are warranted. The showers will spread southward across the remainder of central Illinois Friday morning before the front sinks into the Ohio River Valley and brings an end to the rain chances by Friday night.

The Friday frontal boundary will weaken considerably, then surge back northward into the Great Lakes by Saturday night into Sunday. With only weak forcing in place and an overall lack of deep-layer moisture/instability, think the weekend will be mostly dry. Highs will be in the middle to upper 60s on Saturday, then will soar into the upper 70s and lower 80s by Sunday as southerly flow returns.

The next chance for widespread showers/storms and potential severe weather will hold off until early next week as a pronounced upper trough over the western CONUS begins to shift eastward. Timing of this process remains in question, as the 00z Apr 9 models have all slowed the eastward progression of the main feature. A lead short-wave trough will interact with an increasingly moist atmospheric profile to bring an uptick in showers and thunderstorms Sunday night into Monday morning: however, severe weather chances will remain low due to lack of instability/shear.

With high temperatures in the 80s and surface dewpoints climbing well into the 60s, the atmosphere will become more unstable by Monday afternoon. The 12z LREF shows a 60-80% chance of SBCAPEs greater than 500J/kg and 0-6km shear of more than 30kt along/northwest of a Shelbyville to Champaign line. Despite the favorable parameters, short-wave ridging in the wake of the early morning disturbance and an overall lack of a strong forcing mechanism will keep the severe weather risk low through Monday night.

After that, things become more interesting as the main upper trough shifts slowly eastward. While all models have slowed the system from previous runs, consensus suggests its associated low and cold frontal boundary will come close enough to impact parts of central Illinois sometime during the Tuesday evening through Wednesday afternoon time frame. The LREF indicates the favorably unstable/sheared environment will be in place across all of central/southeast Illinois on Tuesday...and the latest NSSL severe weather probabilities have increased to 15-30% across the board accordingly. While it is still too early to discuss specific risks and timing, it appears an initial round of strong convection may impact central Illinois Tuesday evening into Tuesday night.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

Issued at 553 AM CDT Thu Apr 9 2026

A frontal boundary will stall across north-central Illinois today...with widely scattered showers anticipated near the boundary mostly north of the central Illinois terminals. Have included VCSH at KPIA/KBMI accordingly, but have remained dry at the other TAF sites. All models suggest an increase in convection along the front as it sinks slowly southward later tonight. Based on the latest HRRR/RAP forecast, have carried predominant thunder at KPIA after 08z and at KBMI after 09z. Further south, have only mentioned showers after 10z. Winds will initially be SW with gusts of 15-20kt through early this evening: however, the gusts will increase to 20-25kt this evening as the front approaches.

ILX WATCHES/WARNINGS/ADVISORIES

None.