AIR MAIL
Where today’s air came from
The air arriving over Kabetogama about 5,000 feet above the ground was over the southern Rockies three days ago, and over the southern Plains a day ago, about 1,400 miles back along its path. Most of the nine paths traced from around the city agree. Near the ground the air came from a point about 590 miles to the south; at 10,000 feet, from the central Plains. Traced back 72 hours through NOAA’s hourly RAP analyses, nine paths at each of three heights.