We Could Be Screwed

Just another day in the paradise that is the Wasatch Front.  The latest west-facing image from the University of Utah shows a blanket of smog over downtown Salt Lake City.  

Source: https://horel.chpc.utah.edu/camera_pages/wbbw.html

It's tough to get above it without going to the mid elevations.  I hiked this morning to the top of the Avenues foothills and it was unclear if I was completely out of it even at 5700 feet.  

Recent station (filled squares) and mobile (filled circles) PM2.5 observations show values in the valley generally between about 28 and 45 ug/m3.  

Source: https://utahaq.chpc.utah.edu/

The threshold for unhealthy for sensitive groups is 35.5 ug/m3, so we are seeing values that are near or above that.  The DAQ sensor at Hawthorne Elementary is at 41.3 ug/m3 as of 2 PM.  

Is there hope for a mix out?  The best chance is probably on Thursday and Friday.  On Thursday there is a weak upper-level trough moving over Utah late in the day in the ECMWF HRES forecast.

In the wake of that system, the northerly flow increases and crest-level temperatures drop to perhaps -2°C.  Perhaps the cooling aloft combined with the increased flow can at least give us a partial mix out, but other models are less optimistic than the Euro and it's possible we're screwed.  The GFS forecast for Friday afternoon, for example, still has a capping inversion based at about 825 mb.  In that case, we probably remain exiled in hell.  

Assuming we don't or only partially mix out, we could see the development of fog and eventually stratus that's elevated above the valley floor.  That will make for even more depressing conditions, but in some of those situations cloud base raises with time and produces a deeper mixed layer at low levels.  There's still pollution, but there's a bit more dilution that helps to moderate the PM2.5 levels (although they can still be hazardous).  

Hope for that partial mixout on Thursday and Friday.