textproduct: Central Illinois

KEY MESSAGES

- Another round of thunderstorms will impact central Illinois this afternoon into the overnight. There is a Slight Risk (level 2 of 5) for severe weather west of a Henry to Charleston to Olney line... with the primary risk being damaging wind gusts.

- Beyond tonight, a much needed break from the hot and active weather arrives. Sunday and Monday will have below normal temperatures with highs in the 70s and lows in the 50s.

DISCUSSION

Issued at 233 AM CDT Sat Jun 13 2026

A reinforcing cold front is expected to push through central and southeastern IL today. The SPC has a slight risk (level 2 of 5) for areas west of a Henry to Charleston to Olney line. There could be some morning convection from a decaying MCS traveling across MO overnight. Confidence in the morning showers/t'storms is quite low as the short-range, convective allowing models are not agreeing. For example, the HRRR has some showers/t'storms south of I-74/ west of I- 57 by mid to late morning. The NAMNest keeps the morning round out of the forecast area. The main hazard of concern today is the damaging wind risk this afternoon into the evening, but some small to near severe hail is possible as well. MUCAPE values on forecast soundings in excess of 3000 J/kg, but the instability quickly wanes after sunset. DCAPE is around 800-1200 J/kg. Bulk Shear of 35-45 knots. There could also be a concern for localized flooding as the line of storms move through, especially where the heaviest rain has already fallen over the last week and many rivers are already in flood. Some forecast soundings have a long, skinny CAPE profile to them with PWATS of 1.6-2.0 inches. The storms will weaken as they move east across the state in the late evening into the overnight hours. There looks to be 2 rounds, based off the HRRR. Round one is focused south of I-74, moving east starting at 17z, and exiting out of the southeast around 00z. The second round moving in from the west beginning at 00z, exiting around 10z tomorrow morning.

Beyond tonight, a high pressure center sets up over the region, giving us a much needed break from the hot and active weather. Sunday and Monday will have below normal temperatures with highs in the 70s and lows in the 50s. Temperatures then warm back to near normal, with highs into the 80s by midweek into the end of the week. Rain and thunderstorms will return to the forecast late Tuesday, with the best chances (70-90%) on Wednesday.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/

Issued at 556 AM CDT Sat Jun 13 2026

Some showers are possible this morning for SPI and DEC, but confidence is low. By late afternoon, an area of thunderstorms will move through, impacting each site through the overnight hours, exiting CMI by 10z. Using PROB30s as the guidance still doesn't agree with how the evening/overnight will play out. The timing leans more pessimistic.

Ceilings will deteriorate throughout the 12z period. Borderline MVFR ceilings will move in early tomorrow as the cold front exits to the east. SW winds will shift out of the N behind the front at each site.

ILX WATCHES/WARNINGS/ADVISORIES

None.