AIR MAIL
Where today’s air came from
The air arriving over Highlanding about 5,000 feet above the ground was over southern California three days ago, and over the northern Plains a day ago, about 1,640 miles back along its path. Most of the nine paths traced from around the city agree. It came down from about 10,000 feet up, warming and drying as it sank. Near the ground the air came from the southern Plains; at 10,000 feet, from southern California. Traced back 72 hours through NOAA’s hourly RAP analyses, nine paths at each of three heights.