textproduct: Chicago

KEY MESSAGES

- Seasonable and dry conditions over the weekend, but colder near the Lake Michigan shore.

- Severe thunderstorms Monday along with heavy rain and possible localized flooding.

DISCUSSION

Issued at 237 PM CDT Fri Apr 24 2026

Stratiform rain associated with a passing mid-level wave is now confined almost exclusively east of I-57, and will gradually end from west to east through the afternoon. Thunderstorm potential remains quite low, with the only focus in the far southeast CWA where cloud tops may become barely sufficient for a lightning strike late this afternoon. Farther west, a cold front entering the western CWA will track across the remainder of the area through mid-evening. Abundant cloud cover and slight low-level dry air advection has limited cumulus growth and will likely prevent new precip generation during the remainder of the day.

High pressure drifting eastward across the northern Great Lakes this weekend will promote dry and mostly clear conditions. Temps will be seasonable to seasonably warm well inland. Persistent east to northeast winds will lead to substantially cooler conditions with high in the upper 40s Saturday and mid 50s Sunday along the Lake Michigan shore. Cannot rule out some lake-induced fog or low stratus along the shore each morning as well.

Focus then turns to a potential severe weather event over and west of the area on Monday as deep troughing ejects northeastward over the central Great Plains. Impressive mid and upper-level dynamics shifting between the MO/MS River valleys Monday afternoon should quickly erode a modestly strong cap and force discrete convection around the I-35 corridor. Convection would likely congeal with eastward extend across the MS River, favoring primarily a QLCS set-up over some or all of our area late Monday afternoon and especially Monday evening. The intensity of convection with eastward extent, however, remains somewhat in question due to 1) the ability for less- pronounced forcing farther east to erode the cap and 2) amount of low-level moisture advection as flow remains backed and nearly parallel to a notable moisture gradient. Obviously we are still a few days out to hone in on more details, but conditional on a more favorable thermodynamic farther east, discrete supercells with all severe hazards are a possibility over or particularly south and west of the forecast area, followed by a damaging wind threat with embedded QLCS tornadoes. Will also need to monitor for a flooding threat, especially north of I-88 where river flooding is ongoing, if convection becomes more widespread and/or slower moving.

Behind Monday's system, a transition to longwave troughing over the eastern Great Lakes and eastern Ontario/Quebec will favor a cooler (still seasonable) end to April with perhaps a couple chances for showers later in the week.

Kluber

AVIATION /00Z TAFS THROUGH 06Z SUNDAY/

Issued at 639 PM CDT Fri Apr 24 2026

High pressure will move into the region tonight with northwest winds this evening likely to turn more east of north overnight. While skies will clear out this evening, there is a potential for some low cloudiness to stream in off of Lake Michigan into the immediate Chicago terminals late tonight into Saturday morning. Confidence is very low in the potential for these low clouds with the realistic range of possibilities extending from VFR to IFR. Opted to include a TEMPO for low end MVFR during the time that appears most likely that CIGS could occur (09z-13z), but it is worth stressing again that confidence is very low. The northeast winds off the lake will freshen up at ORD, MDW, and GYY Saturday with some occasional gusts to around 20 kt even possible.

- Izzi

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...None. LM...None.