textproduct: Central Illinois

KEY MESSAGES

- There is a Marginal Risk (level 1 of 5) for severe weather late Tuesday afternoon and evening north of the I-70 corridor. The primary risks will be damaging wind gusts and hail.

- Beneficial rain is on the way for central Illinois this week. There is a 50-80% chance of greater than 2 inches of rain from late Tuesday through Saturday.

DISCUSSION

Issued at 232 PM CDT Mon Mar 30 2026

Severe Weather Risk on Tuesday...

A short-wave trough interacting with a nearly stationary frontal boundary extending from the Plains to the Great Lakes will trigger clusters of thunderstorms from southern/central Iowa northeastward to the Chicago area tonight. Thanks to a strong low-level jet developing after sunset, HREF mean MUCAPEs will peak in the 1500-2000J/kg range...resulting in a risk for large hail with the strongest cells. While the bulk of this activity will remain north of the KILX CWA, a few storms could brush locations along/north of a Macomb to Minonk line after midnight where a Marginal Risk (level 1 of 5) exists.

After a few morning showers/storms across the northern half of the KILX CWA, attention will turn to convective development along a slowly-advancing cold front by late afternoon and evening. As has been noted by the past several model runs, severe weather parameters are not expected to become particularly impressive ahead of the front. Moisture return will be modest as surface dewpoints hover in the upper 50s to around 60 degrees. As a result, HREF mean SBCAPEs only reach 1000-1500J/kg along/north of I-72. With the primary upper forcing remaining well to the north of Illinois, 0-6km shear is progged to be rather modest at 30-40kt. Low-level shear may be a bit more robust further northeast across southern Michigan into northern Indiana/Ohio where severe weather probabilities are higher. Further west along the trailing front across central Illinois, a Marginal Risk (level 1 of 5) for severe weather is currently in place. Based on 12z CAMs, it appears scattered cells will develop along the front along and north of a Jacksonville to Watseka line between 22z/5pm and 01z/8pm, then will become more numerous after dark. Given the instability/shear profile in place, think the primary risks will be a few damaging wind gusts and marginally severe hail north of the I-70 corridor through the evening. While showers and thunderstorms will continue through the overnight hours, the severe weather risk will decrease substantially after midnight.

Beneficial Rainfall This Week...

The Tuesday night cold front will slowly inch southward before it becomes parallel to the upper-level flow and stalls across central Illinois Tuesday night into Wednesday. As a short-wave trough ejecting eastward out of the Plains interacts with the boundary, a wave of low pressure is expected to develop and track northeastward into the Great Lakes by Friday morning. This will bring another wave of widespread showers and a few thunderstorms Thursday/Thursday night. After a brief lull in the action on Friday, yet another wave and its associated cold front will arrive late Friday night into Saturday. Confidence continues to grow that beneficial rainfall will further alleviate the long-term drought conditions across central Illinois this week. The latest LREF highlights a 50-80% chance of greater than 2 inches of rain across the entire area...with a 30-50% chance of more than 3 inches along/north of a Jacksonville to Danville line.

Strong Thunderstorm Potential Next Saturday...

While it is still too early to pinpoint any specific severe weather risk, the final system of the active week ahead bears watching for next Saturday. All models agree that a digging upper trough will push a strong cold front through central Illinois sometime from Friday night through Saturday night. The ECMWF in particular has looked rather ominous over the past few runs, featuring a deepening low tracking from Iowa to Michigan and a trailing cold front passing through central Illinois Saturday afternoon. While machine learning algorithms do not yet have a clear signal for severe, both NCAR and NSSL indicate at least a low probability. Once the front passes, cooler/drier conditions will settle back into the Midwest by early next week.

AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/

Issued at 659 PM CDT Mon Mar 30 2026

Clusters of thunderstorms may affect the central IL terminals late tonight into Tuesday morning as a disturbance interacts with a frontal boundary to the north, then the front will settle southward Tuesday afternoon, moving thunderstorm activity into the area near the end of the period. Have included PROB30 for TSRA for a period in the morning attempting to target the most likely time for storm activity, although lower chances will exist from late tonight through the remainder of the forecast period. Strong winds aloft from the SW around 40-50 kts will promote low level wind shear late tonight into Tuesday morning, although surface winds appear they will be strong enough at KBMI to prevent shear reaching mentionable thresholds. Surface winds SW 15-20 kts with gusts 25-30 kts this evening, diminishing slightly and becoming less gusty after 01Z-03Z. Winds increasing to around 20 kts with gusts around 30 kts by 15Z-17Z.

ILX WATCHES/WARNINGS/ADVISORIES

None.