textproduct: Central Illinois

KEY MESSAGES

- A few thunderstorms will develop along an advancing warm front this afternoon into early this evening. There is a low risk for all severe hazards...with the highest probability of tornadoes (5-10% chance) focused along and north of a Rushville to Bloomington line.

- Another round of convection is expected from late evening through the overnight hours. The primary hazard will be damaging wind gusts...mainly west of the Illinois River.

DISCUSSION

Issued at 231 AM CDT Fri Apr 3 2026

Tornado Risk This Afternoon...

A frontal boundary will drop south of I-70 this morning, then will begin lifting back northward as a warm front this afternoon. The atmosphere in the vicinity of the front will become moderately unstable with HREF mean SBCAPEs around 2000J/kg by peak heating. While deep-layer shear will be rather modest (0-6km bulk shear 30-40kt), enhanced low-level shear near the boundary raises concern for a few tornadoes with the strongest cells. HREF mean 0-3km SRH maximizes further northwest across Iowa in closer proximity to the triple point: however, values of 100-150 are noted further east along the warm front. In addition, 0-3km VGP peaks at around 0.50 along/north of a Rushville to Bloomington line by 00z...where SPC has indicated a 5-10% chance for tornadoes. Based on these parameters and a consistent signal from the HRRR/RRFS, think cells will initially develop just north of I-70 between 18z/1pm and 19z/2pm, then slowly shift northward through the remainder of the afternoon. While there will be a low severe risk with the storms at any time, the enhanced parameters point to a higher chance for a few tornadoes across the NW KILX CWA between 21z/4pm and 00z/7pm.

Another Round of Thunderstorms Later Tonight...

Meanwhile further west, thunderstorms will develop along a cold front from central Iowa to eastern Kansas by late afternoon. Tornadoes and large hail will initially be possible:however, as the cells congeal into a line, the primary hazard will become damaging wind gusts as the storms advance eastward across the Mississippi River by late evening. Latest CAMs still indicate convection arriving in the Illinois River Valley between 10pm and midnight, then pushing eastward across the I-55 corridor between 2am and 4am. With daytime instability waning and upper support/strongest deep-layer shear well to the north, the convective line will gradually lose its punch as it tracks eastward across central Illinois. SPC continues to highlight locations west of the Illinois River with a Slight Risk (level 2 of 5) for severe...with areas further east as a Marginal Risk (level 1 of 5). Will need to keep an eye on later model runs and radar trends as the event begins to unfold, but as of right now...think wind gusts will likely be sub-severe by the time the storms approach I-55.

Quiet/Cooler Weather Early Next Week...

Showers and a few thunderstorms will linger into Saturday morning...especially east of I-55...before coming to an end from west to east during the afternoon. As high pressure builds into the region, a period of chilly weather will be on tap. High temperatures will drop below normal for this time of year into the lower to middle 50s Sunday through Tuesday, while overnight lows dip into the 30s. The coldest period will be Monday night when the LREF suggests a 60-80% chance of readings dropping below 30 degrees along/north of a Macomb to Champaign line.

AVIATION /12Z TAFS THROUGH 12Z SATURDAY/

Issued at 635 AM CDT Fri Apr 3 2026

A warm front will lift northward across the central IL terminals in the afternoon, bringing a period of scattered thunderstorms. There is a risk of strong gusty and erratic winds, heavy rain, and isolated hail with the stronger storms. These storms look to move to the north during the evening, while a cold front and more associated thunderstorm activity approaches from the west. This next round of storms look to arrive by 04Z-08Z. Have included TEMPO for TSRA with MVFR conditions from around 20Z-01Z, but otherwise probability for thunderstorms looks too low for mention until 04Z-08Z. A couple areas of MVFR cigs will persist this morning around KPIA and KCMI this morning, and a period of MVFR cigs will also be possible near the warm front lifting through the area late in the morning to early afternoon. Winds light and variable becoming S-SE 7-11 kts by 17Z.

ILX WATCHES/WARNINGS/ADVISORIES

None.