AIR MAIL
Where today’s air came from
The air arriving over Boyne Valley about 5,000 feet above the ground was over the Pacific Northwest three days ago, and over the Great Lakes a day ago, about 1,830 miles back along its path. It came down from about 14,400 feet up, warming and drying as it sank. Near the ground the air came from a point about 440 miles to the southwest; at 10,000 feet, from the Pacific Northwest. Traced back 72 hours through NOAA’s hourly RAP analyses, nine paths at each of three heights.