AIR MAIL
Where today’s air came from
The air arriving over River Falls about 5,000 feet above the ground was over the northern Plains three days ago, and over the central Plains a day ago, about 1,530 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 10,600 feet up, warming and drying as it sank. Near the ground the air came from Texas; at 10,000 feet, from southern California. Traced back 72 hours through NOAA’s hourly RAP analyses, nine paths at each of three heights.