textproduct: Chicago

KEY MESSAGES

- Periods of rain through tonight with a chance of thunderstorms, highest storm chances early this morning and again this afternoon.

- The potential exists for locally heavy rainfall with localized pockets or corridors of 2"+ rainfall totals.

- High waves and dangerous swimming conditions at Lake Michigan beaches through Monday morning.

DISCUSSION

Issued at 207 AM CDT Sat Aug 1 2026

Low pressure currently near the Quad Cities will slowly move southeast today and tonight as it weakens over the Ohio Valley Sunday. Periods of rain will continue into this evening and then slowly end from northwest to southeast tonight into Sunday morning. The rain may be heavy at times through mid/late morning with rain possibly training over the same areas. There will also be the chance for a few thunderstorms, where rainfall rates will be higher. While rainfall amounts of 2+ inches still remains on track, there is uncertainty for where the highest amounts may fall. While the rain will be spread out over several hours, if the heaviest rains fall over more urban areas, the flooding potential will be higher. Though the general trend will be for precipitation to slowly end tonight, showers will still be possible Sunday morning and perhaps for areas along and east of I-55 until they finally push east into northwest IN Sunday afternoon.

There will also be a chance for funnel clouds across the southeast cwa this afternoon. Not planning any mention in the HWO at this time, but the potential will need to be monitored later today.

Northeast winds are expected to gust into the 30-35 mph range and will create high waves and dangerous swimming conditions at Lake Michigan beaches through Monday morning. Given the long duration of northeast winds, its possible the beach hazard statement may eventually need to be extended into Monday afternoon.

High pressure will build back across the region early next week bringing dry weather and high temps back in the lower 80s. A cold front will move across the Midwest Wednesday into Wednesday night bringing a chance of showers and thunderstorms to the area. cms

AVIATION /12Z TAFS THROUGH 18Z SUNDAY/

Issued at 703 AM CDT Sat Aug 1 2026

Key Messages:

- Showers persist today, with the greatest coverage expected through early afternoon.

- A few embedded thunderstorms are possible this afternoon, mainly south of the terminals.

- Prevailing lower MVFR CIGs and VSBYs expected, with some brief periods of IFR possible with the heavier downpours. - Gusty (up around 25 kt) east-northeasterly winds, particularly this afternoon and evening.

Heavy rain producing showers (with a few infrequent embedded lightning strikes) are currently moving across the Chicago area terminals. This activity has a history of producing brief periods of sub-mile VSBYs. We have handled this in the TAFs with a tempo group through 14Z. Otherwise, scattered showers will persist into at least early this afternoon before the coverage begins to decrease across far northern IL. A few thunderstorms also cannot be ruled out this afternoon, though the primary focus for them looks to become confined farther south across east-central IL into IN through the afternoon. Otherwise, expect little change with CIGs today, with low MVFR CIGs persisting potentially into Sunday morning before improving.

Winds will be gusty today into tonight as the pressure gradient tightens along the northern periphery of the surface low moving across central IL. Currently we anticipate gustiness up to around 25 kt, though some higher gusts up closer to 30 kt cannot be ruled out later today, particularly if CIGs are able to improve more than currently forecast.

KJB

LOT WATCHES/WARNINGS/ADVISORIES

IL...Beach Hazards Statement through Monday morning for ILZ006- ILZ103-ILZ104.

IN...Beach Hazards Statement through Monday morning for INZ001- INZ002.

LM...Small Craft Advisory until 3 AM CDT Monday for the IL nearshore waters.

Small Craft Advisory until 3 AM CDT Monday for the IN nearshore waters.