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KEY MESSAGES

- Generally warm and dry conditions expected through early next week.

- Daily lake breezes will keep temperatures cooler near Lake Michigan, with a couple of back door cold fronts bringing cooler conditions farther inland Thursday and again Saturday.

- Building waves and dangerous currents are expected at Illinois and Indiana Lake Michigan beaches late this evening through Thursday night.

DISCUSSION

Issued at 113 PM CDT Wed May 27 2026

Early afternoon GOES water vapor imagery depicts a fairly stout mid- level short wave propagating south-southeastward across southwestern Ontario and the northern/eastern Great Lakes region. At the surface, a cold frontal boundary stretched from New England, west across the lower Great Lakes, then northwest across Wisconsin into northern Plains. This cold front will be given a southward nudge later today and tonight in the wake of the aforementioned short wave, and enhanced by building surface high pressure across the northern Lakes in the subsident wake of this feature tonight. Ahead of the front, mostly sunny skies have allowed temperatures to warm into the mid 80s (heading for upper 80s/near 90 later this afternoon west) across much of the forecast area, with upper 60s/low 70s closer to the Lake Michigan shore where light onshore lake breeze winds have developed. Farther north, scattered thunderstorms are expected to develop along/ahead of the front by late afternoon, and drift south- southwest across central/southern WI as the front pushes south into early evening. Preponderance of high-res CAM guidance indicates this activity will dissipate across southern Wisconsin with the loss of diurnal heating this evening. Will maintain a dry forecast for the cwa, though have maintained some "silent" (<10%) pops along the IL/WI border through mid-evening and will monitor convective trends in case a stray shower/storm approaches the area.

The main impact from the cold front for us will be breezy northeast winds which will develop behind the boundary later this evening, and persist through Thursday and into Thursday night. Gusty winds around 25 mph will result in building waves on southern Lake Michigan during this period, leading to high waves and dangerous currents for our Illinois and Indiana Lake Michigan beaches. A Beach Hazard Statement remains in effect for this through late Thursday night when winds/waves will gradually subside.

Away from the lake shore, a period of dry and seasonably warm weather will continue into the weekend, as the upper level pattern evolves into an "Omega Block" with a persistent upper level ridge axis focused near/just west of the Mississippi Valley and deep upper level troughs over the east and west coasts. Surface high pressure will continue to settle southward across WI/MI/LM Thursday and across the local area by Friday. This will allow the breezy northeast winds to ease, and diminish the degree of lake-cooling. Highs on Thursday are expected to range from the 60s along the shore to the lower 80s well west and south of the lake. Lighter onshore winds on Friday will allow for 70s near the shore and low to mid-80s inland with highest temps west toward the I-39 corridor. Overnight lows will generally be in the 50s. Current ensemble guidance then indicates another mid-level short wave will dig south-southeast across the eastern Lakes and New England Friday night into Saturday, which for our area looks to bring another northeasterly wind enhancement Saturday and Saturday night with additional lake cooling and the potential for another increased Lake Michigan swim risk.

Not much change in the pattern is expected until early-mid next week, when global ensembles currently indicate a breakdown of the Omega Block across the central CONUS. Until then however, our forecast remains generally dry and seasonably warm (upper 70s and 80s) with varying degrees of lake cooling.

Ratzer

AVIATION /18Z TAFS THROUGH 00Z FRIDAY/

Issued at 1219 PM CDT Wed May 27 2026

No major forecast concerns are expected for this TAF period.

Mostly sunny conditions are expected through this afternoon with northeast winds around 10-12 kts. A cold front will move through the area this evening and will allow winds to increase with gusts around 20 kts expected to prevail tonight into Thursday morning. While the frontal passage is expected to be dry for the terminals, there is a non-zero (<10%) chance for some isolated showers to develop in southern WI and they could brush the areas near the IL-WI line this evening. Otherwise, expect breezy northeast winds to prevail through Thursday with gusts gradually easing Thursday afternoon and VFR conditions.

Yack

LOT WATCHES/WARNINGS/ADVISORIES

IL...Air Quality Alert until 6 AM CDT Thursday for ILZ005-ILZ006- ILZ012-ILZ013-ILZ020-ILZ021-ILZ103-ILZ104-ILZ105-ILZ106- ILZ107-ILZ108.

Beach Hazards Statement from 10 PM CDT this evening through late Thursday night for ILZ006-ILZ103-ILZ104.

IN...Air Quality Alert until midnight CDT tonight for INZ001-INZ002- INZ010-INZ011.

Beach Hazards Statement from 1 AM CDT Thursday through late Thursday night for INZ001-INZ002.

LM...Small Craft Advisory from 10 PM this evening to 10 PM CDT Thursday for the IL nearshore waters.

Small Craft Advisory from 1 AM Thursday to 1 AM CDT Friday for the IN nearshore waters.