textproduct: Chicago

KEY MESSAGES

- Potential for dense fog to develop over Lake Michigan and affect locations along the shore through tonight. Patchy fog possible elsewhere through sunrise Monday.

- Above normal temperatures favored through next weekend, though cooler near Lake Michigan. Rain chances appear low during this period, with chances for showers and storms confined to Wednesday.

DISCUSSION

Issued at 144 PM CDT Sun May 24 2026

High pressure centered just west of the area this afternoon will drift overhead tonight, setting the stage for light/calm winds as skies remain primarily clear. With some (potentially dense) fog already evident over Lake Michigan in the wake of today's rain, will need to closely monitor trends late this afternoon and especially this evening along the Illinois shore as backing low-level flow would then begin advecting any fog onshore. Additionally, patchy shallow fog is possible overnight where rain was more prevalent (around and east of I-55) today. And while low-level will begin veering SSW later tonight subtle WAA acting on any shallow fog south of I-80 would start advecting northward toward the Chicago metro around sunrise. Any shallow fog will quickly dissipate after sunrise.

A small wave/complex of convection over Nebraska and South Dakota late today will drift toward southern Wisconsin and far northern Illinois Monday morning and early afternoon. The thermodynamic environment will become increasingly unfavorable with eastward extent across Iowa and especially east of the Mississippi River. Expectations are for some mid-level clouds and perhaps a few rogue sprinkles in the far northwest CWA midday.

A massive Hudson Bay high developing ahead of a highly amplified ridge over the central/northern Great Plains into central Canada will drift southward midweek into next weekend. Guidance remains mixed on how far north a southwestern CONUS trough becomes cutoff over the southern Great Plains or Lower Mississippi Valley this week. Latest indications are that a vast majority of moisture/forcing associated with the cut off system will remain south of the area, with the exception of a backdoor front bringing a period of showers and some storms to the area Wednesday. Otherwise, dry conditions and seasonably warm temperatures (cooler near the lake) would be expected through much of the period.

Kluber

AVIATION /18Z TAFS THROUGH 00Z TUESDAY/

Issued at 1227 PM CDT Sun May 24 2026

Initial clearing behind this morning's rain has allowed for diurnal mixing into SCT/BKN MVFR cumulus early this afternoon. These clouds should lift while dissipating over the next couple hours.

Light NW winds at TAF issuance will turn E/ESE up to 10 knots with a lake breeze mid to late afternoon (roughly 20Z at MDW and 21Z at ORD). As high pressure shifts over the terminals this evening, winds will settle in the SE quadrant under 5 knots or become calm. Winds will turn SSW late tonight, then increase to around 10 knots on Monday.

Will need to monitor for the potential for dense fog over Lake Michigan late this afternoon and overnight. Given the weak flow, the lake fog should not advect over ORD/MDW, but radiational BR or BCFG will remain possible overnight through daybreak Monday. Included a mention of FEW IFR stratus at MDW given the proximity of FG to the east. Additionally, cannot fully rule out the development of BR/FG south of the Chicago metro late tonight. Given low-level flow veering SSW during this time, dissipating IFR stratus could advect to near MDW/GYY around sunrise.

Kluber

LOT WATCHES/WARNINGS/ADVISORIES

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