textproduct: Chicago

KEY MESSAGES

- Briefly warmer (70s) and windy on Tuesday with the potential for showers and storms.

- Otherwise cooler (60s) and dry conditions are favored through Thursday before a warm-up commences heading into the weekend with additional shower/storm chances.

DISCUSSION

Issued at 313 AM CDT Mon May 11 2026

Surface high pressure will becoming centered over Lake Michigan today. The net result being a steady feed of cool onshore northeasterly flow into our area through the day. Accordingly, another seasonably cool day is expected, with the coolest conditions (upper 40s to low 50s) expected along the southern Lake Michigan shore. Ares farther inland will be a bit warmer, with upper 50s to low 60s looking to be the general theme across much of northern IL, though some areas well inland and south of I-80 could warm a bit more (into the mid to upper 60s) under mostly sunny skies.

Mainly clear skies, light winds and low surface dewpoints ( in the upper 20s to around 30) tonight should then support efficient radiation cooling after sunset, with main locations outside urban areas of Chicago dropping into the upper 30s to low 40s overnight. This may thus promote some patchy frost development late tonight, particularly across far northeastern IL and northwestern IN where temperatures could briefly fall below 38 degrees late tonight. Currently, the coverage of frost looks too low to support the need for a frost advisory. Nevertheless, anyone with sensitive outdoor vegetation in these areas should plan accordingly.

The primary forecast attention through the period will be focused on our next weather maker, which is set to evolve out of the impulse traversing the Canadian Rockies atop the southwestern CONUS upper ridge axis today. Ensemble guidance continues to favor this impulse, along with an associated surface low, diving southeastward along the northeastern periphery of the southwestern ridge. This would generally result in a southeasterly track right across the Upper Midwest late tonight, then into the western Great Lakes region on Tuesday. A strong southerly mass wind response in advance of this system will result in winds across our area quickly turning back to the south-southwest and increasing in magnitude during the day Tuesday. Accordingly, this is expected to result in a rather windy day in our area Tuesday, albeit a warmer one. Model soundings are ubiquitous in indicating diurnal mixing into 40+ kt flow just a few thousand feet above the surface during the afternoon, which could certainly support surface gusts topping 35-40 mph.

In addition to the windy conditions on Tuesday, we also continue to monitor the potential for showers and storms, particularly in the afternoon and evening. Warm advection on the strong southwest winds will drive temperatures back into the 70s during the afternoon in advance of an approaching cold front. However, low-level moisture return on these winds looks to remain modest, owing to surface high pressure ridging across the southern states blocking the better Gulf moisture. Accordingly, this adds questions as to the extent of airmass destabilization that take place in advance of the front Tuesday afternoon, particularly considering there may also be some warm air advection driven mid-level cloud cover and showers shifting across northern IL during the late morning into the afternoon. Nevertheless, the presence of strong deep layer flow suggests that if the warm sector airmass is able to destabilize just ahead of the front as a result of potential better moisture pooling, conditions would be supportive of organized isolated strong convection during the afternoon and evening. This potential on Tuesday is highlighted by the SPC as a level 1 of 5 severe weather threat. Temperatures briefly cool down again following Tuesday evenings cold frontal passage. Breezy northerly winds setting up in its wake into the day Wednesday will keep high temperatures in the low to mid 60s. Temperatures then will be on a gradually warming trend through the end of the week as upper-level ridging builds across the central CONUS and into the Upper Midwest by the weekend. The degree of warmth continues to remain in question given the potential for a period of more active weather later in the week possibly moderating things a bit. Blended guidance has accordingly trended a bit cooler with the latest update, with forecast highs in the mid 70s to lower 80s over the weekend.

KJB

AVIATION /12Z TAFS THROUGH 18Z TUESDAY/

Issued at 620 AM CDT Mon May 11 2026

VFR conditions with passing mid to upper-level clouds will persist through the period. NE winds of 10 to 15 knots with sporadic gusts to 20 knots are expected today. Expect ENE/E winds under 10 knots this evening to gradually increase to around 10 knots while veering S by sunrise Tuesday. Winds will then quickly increase and veer SSW with gusts to 25 knots Tuesday morning. Beyond the TAF period Tuesday afternoon, SW winds will gust over 30 knots with a potential for scattered showers and a few TS late in the afternoon.

Kluber

LOT WATCHES/WARNINGS/ADVISORIES

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