Yesterday morning we discussed how a meteorological inversion had developed, but that the air quality was still good to moderate. There just wasn't time yet for emissions to accumulate within the valley cold pool.
However, by late afternoon, it was clear that the air quality was declining, with smog evident over the Salt Lake Valley as the sun set over the Oquirrhs.
The situation above is not uncommon. The reality is that the air quality in the West Valley is often worse than on the east bench. This is a consequence of several factors including spatial patterns of emissions, elevation, and circulations such as cleaner canyon outflow jets in the morning on the east side.