AIR MAIL
Where today’s air came from
The air arriving over West Branch about 5,000 feet above the ground was over the Great Lakes three days ago, about 620 miles back along its path. Most of the nine paths traced from around the city agree. It came down from about 9,800 feet up, warming and drying as it sank. Near the ground the air came from the Great Lakes; at 10,000 feet, from a point about 470 miles to the southwest. Air off the water carries moisture, which is why it feels humid. Traced back 72 hours through NOAA’s hourly RAP analyses, nine paths at each of three heights.