Cold lake and Canadian snowpack behind chill

Blame a late season snowpack still in place over sections of southern Canada and the chilly waters of Lake Michigan for the late February level temperatures expected to dominate most of Friday. Computer-generated wind trajectories indicate the chilly air here Friday was situated in central Ontario Province, Canada, Thursday. Powerful NE winds have forced the chill on a trek into the metro area, much of it over the cold waters of Lake Michigan. The time incoming air spends over the cold water is directly related to the wind direction and is critical in determining how chilly temperatures are likely to be once they reach the city. The NE winds which blow as the day begins travel across just 120 miles of water before reaching Chicago. But these winds are to become more northerly and by evening will be entering the city after a near 290 mile trip over cold water. Temperatures are likely to decline during the day.
-Tom Skilling