AIR MAIL
Where today’s air came from
The air arriving over Lake Shore about 5,000 feet above the ground was over the southern Rockies three days ago, and over the southern Plains a day ago, about 1,430 miles back along its path. It came down from about 14,000 feet up, warming and drying as it sank. Near the ground the air came from the Mississippi Valley; at 10,000 feet, from the southern Rockies. Traced back 72 hours through NOAA’s hourly RAP analyses, nine paths at each of three heights.