AIR MAIL
Where today’s air came from
The air arriving over Westfield about 5,000 feet above the ground was over a point about 260 miles to the south three days ago, and over the Mississippi Valley a day ago, about 580 miles back along its path. The nine paths traced from around the city fan out, so treat that as a best guess. Near the ground the air came from the Great Lakes; at 10,000 feet, from the central Plains. Traced back 72 hours through NOAA’s hourly RAP analyses, nine paths at each of three heights.