AIR MAIL
Where today’s air came from
The air arriving over Poplar River about 5,000 feet above the ground was over a point about 940 miles to the south three days ago, and over the central Plains a day ago, about 1,260 miles back along its path. Most of the nine paths traced from around the city agree. It rose from near the ground on the way. Near the ground the air came from the southern Plains; at 10,000 feet, from the northern Plains. Traced back 72 hours through NOAA’s hourly RAP analyses, nine paths at each of three heights.