AIR MAIL
Where today’s air came from
The air arriving over West Valley about 5,000 feet above the ground was over the northern Plains three days ago, about 1,370 miles back along its path. The nine paths traced from around the city fan out, so treat that as a best guess. It came down from about 9,200 feet up, warming and drying as it sank. Near the ground the air came from Texas; at 10,000 feet, from southern California. It feels humid. Traced back 72 hours through NOAA’s hourly RAP analyses, nine paths at each of three heights.