A lake-effect snow event will impact parts of our area nearest Lake Michigan late tonight into Friday morning, with the potential for up to 6″+ in isolated spots. Characteristics of lake-effect snow make for a tricky forecast, as several variables are involved.
Snow will drift southward over Lake Michigan and begin in Northwest Indiana after 10 pm. As the system travels south it will likely shift westward, affecting eastern Will County and southeast Cook County. Just how far west the system tracks will determine which areas see snow tonight, as sharp snowfall gradients are typical of lake-effect snow.
While the heaviest snow should center on northeast Indiana, southeast Cook and eastern Will, snow may fall farther north through Lake County, Illinois, along Lake Michigan. Generally, areas along and west of I-355 should miss out on most of the activity, though flurries are possible. Rates of 1-to-2″ per hour may occur at times where the heaviest snow bands form.
Because lake-effect snow does not fall evenly, accumulations will vary widely from one location to another. The highest amounts of 6″+ are forecast for northeast Indiana; 2-4″ in southeast Cook and eastern Will; and potentially up to 2″ in areas nearest Lake Michigan from Chicago into Lake County, should snow reach that far north.
A Winter Storm Watch will be effective from midnight through noon on Friday for southeast Cook County and Lake County, Indiana, for the potential of heavy snow rates of 1-2″ per hour, reduced visibility and hazardous travel conditions.