textproduct: Central Illinois

KEY MESSAGES

- Scattered thunderstorms may develop ahead of an advancing cold front this afternoon into early evening, with a slight risk (level 2 of 5) for severe storms near and south of Interstate 70. Damaging winds and heavy rainfall are the main hazards.

- Drier and cooler weather returns briefly for midweek. The pattern turns unsettled once again late this week into the weekend with several opportunities for showers and scattered storms.

DISCUSSION

Issued at 109 PM CDT Tue May 19 2026

Midday surface analysis shows a ~1004 mb low north of the Great Lakes Region in southeast Ontario with a trailing cold front stretched from northern Michigan through the middle Mississippi Valley. Ahead of the front, a few remnant outflow boundaries from overnight convection are noted with the most predominant one stretched from roughly Robinson to Lawrenceville as of 1 pm. This boundary is moving steadily to the east and will likely be the main focus for scattered thunderstorm development later this afternoon into evening. Dewpoints in the upper 60s to low 70s out ahead of the front/outflow boundary have allowed SBCAPE to become moderately strong. More favorable deep layer shear will be displaced closer to the cold front, though high PWATs and steep low-level lapse rates may be enough to support a few damaging wind gusts. The 12Z CAMs have shown a shift eastward with storm activity, with the focus being southeast of a Terre Haute to Flora line through early evening. The 19.12Z HREF 24 hour LPMM shows localized pockets of 1- 2"+ of rain occuring with storms, which looks to be south and east of the hardest hit rain areas from yesterday.

The cold front will work through the area this evening, reaching the Ohio Valley around midnight. Much of the precipitation should come to an end as the front moves through later this evening. However, a shortwave trough lifting from the southern Plains into the Tennessee Valley will nudge the front back northward overnight and spread light shower and isolated thunder chances back into southeast parts of the state through Wednesday morning. High pressure ridging will increase large-scale subsidence and ultimately push the front back south of here, putting an end to the precipitation by Wednesday afternoon.

High pressure will shield us briefly from precipitation, with cooler and drier conditions expected through much of Thursday. A western trough will work into the central US and spawn several shortwaves into the Midwest states late this week through the weekend, bringing the return of scattered precipitation chances. Temperatures and moisture will steadily increase through the weekend and may support the development of thunderstorms at times. However, overall weak forcing should largely mitigate any chances for severe weather through early next week. Machine learning probabilities support this by keeping any chances for severe weather south of here.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 1230 PM CDT Tue May 19 2026

West-southwest winds will shift to the north-northwest as a cold front works through the area. A short period of MVFR ceilings will fill behind the front with about a 60-80% chance of occurrence at all airfields except KCMI. Afternoon/evening thunderstorm chances will remain south of all airfields with perhaps just a low chance (<20%) for isolated showers through this evening. Winds continue to veer to the north by Wednesday morning with clouds slowly lift from west to east through the day.

ILX WATCHES/WARNINGS/ADVISORIES

None.