AIR MAIL
Where today’s air came from
The air arriving over White Bear about 5,000 feet above the ground was over a point about 380 miles to the south three days ago, and over the southern Plains a day ago, about 830 miles back along its path. It came down from about 9,600 feet up, warming and drying as it sank. Near the ground the air came from the Ohio Valley; at 10,000 feet, from the southern Plains. Traced back 72 hours through NOAA’s hourly RAP analyses, nine paths at each of three heights.