AIR MAIL
Where today’s air came from
The air arriving over Stone Lake about 5,000 feet above the ground was over a point about 380 miles to the south three days ago, and over the southern Plains a day ago, about 820 miles back along its path. Most of the nine paths traced from around the city agree. It came down from about 9,100 feet up, warming and drying as it sank. Near the ground the air came from the Great Lakes; at 10,000 feet, from a point about 500 miles to the south. Traced back 72 hours through NOAA’s hourly RAP analyses, nine paths at each of three heights.