textproduct: Central Illinois

KEY MESSAGES

- An Enhanced Risk (level 3 of 5) for severe weather exists east and north of a Havana-Springfield-Mattoon line late this afternoon and evening. Damaging wind gusts in excess of 75 mph, hail greater than 2 inches in diameter, and tornadoes (EF2+ strength) are possible.

- Large temperature swings are in store starting tonight. Readings will soar to record warm levels in the middle to upper 80s, nearing 90, today...then will plunge into the middle to upper 20s by early Saturday morning.

DISCUSSION

Issued at 240 AM CDT Thu Mar 26 2026

As an 850 mb warm front lifts across central IL this morning, there are some showers and thunderstorms that are moving through. Before the cold front arrives today, we will be flirting with near 90 temperatures. Then the cold front will bring strong to severe storms, potential excessive rainfall, and a sharp drop off in temperatures this evening. After this system, we should be dry through Sunday afternoon before rain chances return.

There a 40-70% chance of greater than 85 degrees south of I-74, from the HREF. The probabilities increase to 70-100% as you get southwest of a Macomb to Taylorville line. We are looking at blowing away the record highs today, and maybe even record monthly highs, as the records are around 78-85 degrees. (See climate section for locations and records)

SPC has central IL a slight/enhanced risk (level 2/3 of 5) for severe weather for today. All hazards are in play, large (potentially 2+ inch) hail, damaging winds (potentially 75+ mph gusts), and a few tornadoes. SPC suggests that if there is a tornado, there is the chance for it to be of EF2 or greater strength. Timing looks to have the storms developing just north of the forecast area around 21-23z, initially being discrete. Then the storms will eventually transition to linear later in the evening. They would exit to the south by 08-10z Friday morning. The severe risk, however, will not be around that whole time, as we lose the daytime heating. As the line moves towards southeastern/southern IL, the severe threat will diminish towards midnight. Showers and thunderstorms would continue into early tomorrow morning as it completes its pass through southeastern IL.

The environment appears primed for this afternoon but will have to fight a cap initially, but as the front approaches, the cap will erode. There is a signal that the storms could potentially develop along or behind the front. If they develop behind the front, we would more likely be dealing with elevated storms, with more focus on the very large hail (2+ inch) risk. The tornado risk will be with any storms that latch onto the boundary. The HREF shows SBCAPE values of 1500-2000 J/kg, with 40-50 knots of shear. Lapse rates sound alarm bells for significant hail sizes with insane values of 8- 8.3 C/km as seen on forecast soundings. For the wind risk, the forecast soundings have an "inverted-v" profile with DCAPE values 1000-1400 J/kg. Then the PWATs, which are around 1.4-1.6, and the long skinny CAPE profile suggest that these storms could be efficient rain producers. The WPC maintained a marginal risk for excessive rainfall for today.

Behind the front, lows tonight will dip down into the mid 30s to low 40s. Highs on Friday won't be much warmer, with values in the upper 40s to low 50s. As of now, there is a 30-50% chance that temperatures will get back above 80 degrees southwest of a Avon to Taylorville line by next Monday.

AVIATION /18Z TAFS THROUGH 18Z FRIDAY/

Issued at 1249 PM CDT Thu Mar 26 2026

CAMs continue to suggest rapid convective development near or just northeast of the I-74 corridor between 21z and 23z. HRRR/RRFS have consistently shown cells firing northeast of KPIA, then tracking E/SE into Indiana by around 00z. Based on the latest data, have maintained the PROB30 group for thunder at KPIA between 21z and 23z, but have gone with TEMPO severe thunder/hail at both KBMI and KCMI. Once this initial cluster of storms exits, additional convection will develop along/north of an advancing cold front during the evening. With all models showing storms becoming widespread, have opted to go with predominant thunder at all terminals...with the thunder ending from north to south between 05z and 07z. Winds will initially be SW with gusts of around 25kt this afternoon, then will switch to NE and gust 30-35kt behind the cold front this evening into the overnight hours. After FROPA, MVFR ceilings will overspread the area...with HRRR/NAM forecast soundings showing the low clouds persisting through midday Friday.

CLIMATE

Issued at 125 AM CDT Wed Mar 25 2026

Forecast temperatures on Thursday may exceed March records in some areas.

Mar 26 Record March Record Charleston.... 84 (1907) 89 (3/24/1929 and 3/22/2026) Decatur....... 83 (1907) 89 (3/24/1929) Jacksonville.. 83 (1950) 91 (3/21/1907) Lincoln....... 83 (1991) 86 (3/29/1985 and 3/30/1986) Normal........ 83 (2007) 88 (3/21/1907) Olney......... 85 (1907) 89 (3/24/1910 and 3/24/1929) Peoria........ 82 (1907/1991) 87 (3/21/1907) Springfield... 81 (1991) 91 (3/21/1907) Urbana........ 81 (1907) 85 (3/21/1907 and 3/24/1910)

ILX WATCHES/WARNINGS/ADVISORIES

None.