A shift in the wind overnight has given us a temporary reprieve from the smoke in the Salt Lake Valley, but brought in some clouds that kept it remarkably warm overnight.
Many of the features in yesterday (Monday) morning's sounding at the Salt Lake City airport were typical of July with an inversion at the surface (which burns off rapidly with morning heating) and then what is known as an "inverted V" profile up to about 500 mb. The inverted V is characteristic of something known as the residual layer, a remnant of the previous days boundary layer in which thermals generated by surface heating mix the atmosphere. The flow was light at low levels and northwesterly aloft, the latter bringing in smoke from upstream sources.
If one believes the HRRR, "periods of smoke" is probably the best forecast one can make. The air to our south and southwest is less smoky at low levels, but to our north and west is quite smoky. Given the shifting winds over the next day or two, we will probably see a lot of variability in smoke. You can see in the smoke forecast for 0600 UTC (midnight) tonight that high smoke concentrations come in with a shift to northwesterly flow tonight, but there are lower concentrations just to the south. Subtle variations in the wind will make a pretty big difference.