textproduct: Central Illinois

KEY MESSAGES

- Isolated Severe Storms through Saturday: Scattered thunderstorms this afternoon and evening will bring a threat of isolated damaging winds and large hail to areas along and south of a Shelbyville to Terre Haute line. There is a marginal to slight risk of severe storms Friday afternoon into Friday evening across the same area (slight risk south of I-70), with isolated damaging winds, large hail and isolated tornadoes possible especially south of I-70. There is a marginal risk of isolated severe storm threat will continue Saturday afternoon into Saturday evening but will shift to areas along and south of I-74.

- Heavy Rainfall and Flooding: Multiple rounds of storms will bring a heavy rainfall and flood threat from late this afternoon through Saturday morning. There is a 60-80% chance that rainfall totals will exceed 1.5 inches for locations along and south of a Jacksonville to Paris line where a Flood Watch is posted.

- Dangerous Heat Next Week: A prolonged period of oppressive heat and humidity builds into the region Sunday afternoon through Thursday. High confidence exists that daily heat index values will consistently be around or above 105 degrees across the area during the afternoon hours Monday through Thursday.

DISCUSSION

Issued at 245 PM CDT Thu Jun 25 2026

We continued the Flood Watch from Scott, Morgan, Sangamon, Macon, Moultrie, Douglas and Edgar counties south from 4 pm today until 1 pm Saturday. Between 1.5 and 3 inches of rain is likely with locally higher amounts. The LPMM guidance is showing pockets of 2-3 inches of rain in less than 6 hours over central and southern portions of CWA through Friday evening. WPC has marginal to slight chance of excessive rainfall through Fri night over central and southeast IL, with the slight chance over southern CWA/southeast IL. Will need to monitor closely if flood watch is needed to expand another tier of counties northward. We are already seeing slow moving thunderstorms producing 1-2 inches of rain per hour south of an Effingham to Robinson line. An isolated thunderstorm was west of Paris in southern Edgar county. Tropical like PW values are 1.5-1.75 inches over southeast IL.

In addition to the heavy rains, we have marginal risks of severe storms this afternoon into mid evening along and south of a Shelbyville to Terre Haute line for 5 to less than 10% risk of damaging winds and hail. SPC Day2 outlook has marginal to slight risk of severe storms Fri afternoon/evening in same area, with the slight risk south of I-70 where there is a 5% to less than 10% risk of tornadoes. The strong to potentially severe cells we had in southeast IL this afternoon are located in unstable airmass with MLCAPES 1500-2200 j/kg from Shelby and Edgar counties south. Meanwhile have 40-50 kt bulk shear values in east central IL and this values are forecast to weaken to 30-40 kts into mid evening.

Low pressure over southeast CO to track eastward into east central/se IL Friday evening and will see increasing moisture ahead of system into central IL. Have chances of showers and thunderstorms increasing from se to ne during overnight into Friday and diminishing during Friday night. PW values likely reach 1.75-2.1 inches on Friday supporting heavy rain threat. Unstable air mass in southeast IL also supports severe wx risk Fri afternoon/evening. Convection chances to become more scattered Saturday and Saturday night as system pulls away. Could still be some isolated convection Sunday especially Sunday afternoon over ne CWA.

Main weather story next week will be the high heat and humidity building Sunday/Monday and continue through much of next week. Highs climb from lower 80s Saturday to upper 80s/lower 90s Sunday with afternoon heat indices upper 90s to lower 100s Sunday afternoon. Even hotter Monday through Thu with highs in the low to mid 90s and afternoon heat indices around or above 105F. We will likely need heat headlines next week especially Monday through Thursday.

AVIATION /18Z TAFS THROUGH 18Z FRIDAY/

Issued at 1151 AM CDT Thu Jun 25 2026

Clouds will gradually increase this evening in the vicinity of a surface front displaced just south of the regional terminals. Overnight into Friday morning, these clouds will thicken and lower as the surface front slowly lifts northward. MVFR ceilings are forecast to spread over the regional terminals between 08z-12z, with widespread showers forecast to move in during or just after that time and persisting for the remainder of this TAF cycle. Visibility may also occasionally fall into the MVFR range within heavier bands of showers.

Surface winds will gradually veer, becoming east between 5-10 kts by Friday morning as the surface front moves over the region.

ILX WATCHES/WARNINGS/ADVISORIES

Flood Watch through Saturday afternoon for ILZ049>057-061>063- 066>068-071>073.