AIR MAIL
Where today’s air came from
The air arriving over Sanborn about 5,000 feet above the ground was over the northern Rockies three days ago, and over the Great Lakes a day ago, about 1,540 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 Great Lakes; at 10,000 feet, from the California coast. Traced back 72 hours through NOAA’s hourly RAP analyses, nine paths at each of three heights.