CHICAGO, IL — A Winter Weather Advisory is in effect for parts of the Chicago suburbs and all of Lake County, Indiana, beginning at midnight and running through 10 a.m. Friday. Forecasters say a round of lake effect snow could move in overnight after rain changes over as temperatures fall.
The National Weather Service expanded the advisory Thursday to include southern Cook County and eastern Will County in Illinois. The first alert had already been posted for Indiana earlier in the day, and the timing points to the overnight hours as the period with the greatest travel risk.
Rain is expected to flip to wet snow after sunset
Thursday’s weather is expected to start with lake-effect rain across northwest Indiana, along with gusty winds and temperatures in the 40s. As the sun goes down, that rain should transition to wet snow, setting up the possibility of minor accumulation overnight.
Forecasters say snow is most likely to build near the state line, with the strongest chance for accumulation in Northwest Indiana. Even where totals stay limited, the change in precipitation type could make roads more slippery during the evening and overnight commute windows.
Up to 3 inches could fall near the Illinois-Indiana border
Localized snowfall totals of up to 3 inches are possible, especially close to the border between Illinois and Indiana. The National Weather Service says those amounts could lead to road impacts in the advisory area, even if the snow does not last long on the ground.
The combination of warmer pavement and marginal overnight temperatures means accumulations are not expected to stick for extended periods. Still, a brief burst of heavier snow could be enough to reduce visibility and leave slushy or slick stretches on untreated roads.
Temperature differences will shape where snow sticks
Temperatures are expected to fall to freezing in the suburbs overnight, while the lakeshore should stay milder in the mid-30s. That temperature split matters because it can change how quickly the wet snow accumulates and how long it lingers on pavement and shoulders.
Friday’s highs are forecast to reach the lower 40s, which should limit the chance for snow to hang around for long. Even so, the colder inland areas may see more noticeable impacts before morning temperatures rise later in the day.
Friday morning commuters are being warned about slick roads
Officials are urging drivers to leave extra time Friday morning and to be cautious on the roads. The biggest concern is not a major snowstorm, but a short window of hazardous conditions when wet snow, freezing temperatures and reduced visibility could overlap before work hours.
That risk is highest in the advisory zone near the Illinois-Indiana border, where even a modest snowfall can affect traffic. For commuters, the main message is to plan for slower travel early Friday and to watch for changing conditions overnight.
The advisory follows an afternoon expansion into Illinois
The warning began with Lake County, Indiana, before it was broadened around 12:30 p.m. to cover nearby Illinois counties. That expansion shows forecasters tracking the snow band as it developed and adjusted the coverage area as conditions became clearer.
For residents in southern Cook County and eastern Will County, the new advisory means the overnight weather could be enough to complicate the morning drive even without a prolonged storm. The key window remains from midnight until late Friday morning, when road conditions are expected to be most affected.