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 /00Z TAFS THROUGH 06Z TUESDAY/

Issued at 630 PM CDT Sun May 24 2026

Primary forecast concern is fog potential overnight into early Monday morning.

A slow moving lake breeze has moved west of ORD/MDW late this afternoon and will likely dissipate near or east of a DPA/LOT line with sunset. While patchy fog will be possible across much of the area, this boundary may allow for a narrow and localized area of thicker fog to develop overnight, though confidence is low. Dense fog is expected over Lake Michigan which may move along the shore. Opted to make no changes to the current forecast with prevailing mvfr vis at GYY/DPA and only 6sm at ORD/MDW. Further northwest at RFD, fog potential seems to have diminished some but is still possible. Any fog that does form will quickly dissipate after sunrise Monday morning.

Northwest winds continue west of the lake breeze but winds will eventually become light southeast across the entire area later this evening and then light southerly overnight, with many areas possibly becoming light and variable or calm. Winds look to turn southwest or possibly west/southwest after daybreak and will then slowly turn back southerly by early afternoon and possibly south/southeast by late Monday afternoon/early Monday evening. A lake breeze is expected Monday afternoon, but confidence is low for how far inland it may move. cms

LOT WATCHES/WARNINGS/ADVISORIES

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