AIR MAIL
Where today’s air came from
The air arriving over Medina about 5,000 feet above the ground was over the Great Lakes three days ago, about 940 miles back along its path. The nine paths traced from around the city fan out, so treat that as a best guess. It came down from about 9,500 feet up, warming and drying as it sank. Near the ground the air came from Quebec; at 10,000 feet, from the Great Basin. Traced back 72 hours through NOAA’s hourly RAP analyses, nine paths at each of three heights.