textproduct: Chicago

KEY MESSAGES

- Gusty southwest winds the remainder of the afternoon, with some spotty blowing dust near open farm fields.

- Showers and thunderstorms are likely Monday evening, with shower chances persisting into Tuesday. A few storms late Monday afternoon and evening could be strong to severe with threats for hail and strong winds (mainly near and south of I-80).

- Outside of a brief warmup today Monday, near to below normal temperatures are favored through next weekend with occasional chances for rain showers.

DISCUSSION

Issued at 217 PM CDT Sun May 3 2026

Rest of this afternoon...

Gusty (up to ~35 mph) southwest winds will continue through sunset this evening. In spite of the recent light rain, there have been some recent reports of blowing dust in and near open farm fields. Therefore, some localized reduced visibilities may continue to be experienced in open areas, particularly near any recently plowed/planted fields.

Tonight onward...

A vigorous mid/upper trough digging/diving south across the Canadian Rockies will drive a deepening surface low east- southeastward into southern Ontario late tonight into Monday. As it does, a west-southwest trailing cold front will sweep southward into the Upper Midwest and western Great Lakes through the day Monday, then across northern IL and northwestern IN Monday evening/night. In advance (south) of this approaching frontal boundary, breezy southwest winds, gusting to 30-35 mph during the day, will drive temperatures up well into the 70s, if not into the low 80s for afternoon highs. An influx of slightly better low-level moisture will also accompany these warmer conditions, but afternoon mixing is likely to limit the climb of surface dewpoints into the lower 50s. This thus adds questions as to the amount and coverage of any afternoon showers and storms across our area Monday afternoon.

In spite of the lack luster low-level moisture Monday afternoon, a few isolated to widely scattered afternoon showers and storms cannot be ruled out, particularly in my northwestern northern IL counties in close proximity to the approaching surface front. Also, another axis of possible afternoon showers and storms will exist in the southeast of I-57 in closer proximity to the track of a mid-level impulse. Both of these areas have low (20-30%) chances for storms Monday afternoon. Locally strong wind gusts and some possible hail could accompany any storms that develop in the afternoon.

Shower and thunderstorm chances will quickly ramp-up during the evening hours (likely around and after sunset) as the cold frontal boundary moves into northern IL and larger scale forced ascent increases. This appears to especially be the case near and south of the I-80 corridor after sunset as frontal moisture convergence strengthens in the proximately of a 35-40 kt southwesterly low-level jet extending into the lower Great Lakes. While confidence with this period of showers and storms in the evening continues to increase, the overall severe threat remains of low confidence, owing to the presence of modest instability during a diurnally unfavorable time. Still, some of the stronger storms in the evening around and south of the I-80 corridor may become capable of producing localized damaging winds and instances of marginally severe hail (hail to 1" in diameter).

The threat of storms should abate after midnight Tuesday morning, though rain/shower chances will linger on Tuesday. This looks to particularly be the case well south of I-80 across central and southern portions of IL and IN in closer proximity to a frontal wave of low pressure expected to track northeastward into the Ohio Valley Tuesday evening. Otherwise, the main weather story on Tuesday will be the turn towards much cooler conditions. High temperatures are currently forecast to remain in the 50s during the day, with the coolest conditions near Lake Michigan, where temperatures may only top out around the 50 degree mark.

Aggregate troughing and northwest flow over the Great Lakes and Midwest will then be the theme for the synoptic upper-level pattern into next weekend. This will favor the persistence of below normal temperatures through the mid to late week period. We will also have additional periodic opportunities for rain showers in the coming days as more disturbances embedded within the mean longwave troughing and northwesterly flow aloft dive into the region.

KJB

AVIATION /00Z TAFS THROUGH 06Z TUESDAY/

Issued at 637 PM CDT Sun May 3 2026

Aviation Forecast Highlights:

- Breezy southwest winds quickly diminish after 01z.

- Another increase in southwest winds Monday morning, with gusts 20-25 kts after 15z.

- Frontal system tracks through the region after 00z Tuesday, bringing shower and thunderstorm chances.

Breezy southwest winds this evening will quickly diminish, after sunset across the region. Clouds are forecast to decrease overnight bringing mostly clear skies across northern Illinois into northwest Indiana.

VFR conditions continue on Monday as southwesterly winds increase, with gusts of 20-25 kts, ahead of the next frontal system. This cold front will track through the region Monday evening into the overnight, with forecasts for ORD and MDW showing impacts after 00z. Introduced -SHRA, with a PROB30 for TSRA, between 01-04z. Will need to introduce SHRA/TS chances at remaining terminals with the 06Z TAF issuance.

Baker/Ratzer

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...None. LM...Small Craft Advisory until 7 PM CDT this evening for the IL and IN nearshore waters.