Today's air quality across the nation was generally good, with scattered Code Yellow (Moderate) PM2.5 conditions in the Plain and Great Lake states (top left, courtesy AIRNow). PM2.5 conditions in Utah have improved since yesterday, however the region did peak this afternoon at Code Orange (Unhealthy for Sensitive Group) levels (top right,courtesy AIRNow). According to the HMS analysis team, aerosols of unknown origin were observed stretching west from Florida through the central Gulf of Mexico. A stationary frontal system is juxtaposed to the aerosols, which may be keeping the airmass confined. This afternoon's MODIS pass aboard the Terra satellite shows slightly elevated AOD in this region, however is difficult to depict due to cloud contamination (bottom left). The LANCE Rapid Response snapshot over the Gulf also shows what appears to be haze towards the bottom left of the image (bottom right). Finally, Ray provided us with some pictures from above of hazy conditions in Phoenix, Arizona today (bottom).