A remarkable dust storm has been raging over the Salt Lake Valley now for a few hours. As is often the case, the dust became very concentrated along the cold front, resulting in what I'll call Black Storm conditions. The Black Storm is a name commonly used for intense dust storms over China.
Evidence for the extreme nature of the dust is provided by visibilities at the Salt Lake City International Airport, which dropped to a half mile immediately following frontal passage. In addition, observations at the University of Utah show a nearly instantaneous temperature fall from 70ºF to 52ºF with a concurrent PM2.5 spike to over 210 ug/m3. For reference, the clean-air act standard is 35 ug/m3 (24-hour average).
I've been sheltering inside, but I'm sure the frontal passage was positively miserable to experience outside.