If you looked outside this afternoon and looked up you would have noticed a light haze. Particularly noticeable later in the afternoon with the setting sun. A quick run of the Hysplit model in the backward mode showed the source region of the haze. Below is a backtrajectory map from Las Cruces examining the air 5 days in the past. The past 24-hour showed the air from the southeast along the Rio Grande. Going back even further the airmass made a turn along the path of the high pressure center and passed through the upper Midwest and through the northern Plains.
