Thursday, May 7, 2020

Yesterday's Dust Storm

Strong north-northwest winds late yesterday afternoon came accompanied with dust originating likely from southern Idaho and briefly elevated PM2.5 levels over the Salt Lake Valley.

Observations from the Neil Armstrong academy show a clear trough passage in the northern Salt Lake Valley at around 1800 MDT.  The trough passage was accompanied by an abrupt increase in wind speed (red line) and wind gusts (green plus signs) as well as a wind shift from predominantly west-northwest to predominantly northwest-north. 

Source: MesoWest
Accompanying the trough and the stronger winds was dust, with a spike in PM2.5 to just over 45 ug/m3.  PM2.5 concentrations remained above 10 ug/m3 for about 2 hours and 5 ug/m3 for an additional 3 hours. 

Source: MesoWest
Modis satelite imagery suggests that agricultural fields in the Snake River Plain may have been a source for at least some if not much of the dust.  In the image below, you can see the dust in the Snake River Plain northwest of the Great Salt Lake.

Source: MesoWest
I can't rule out contributions from sources in Utah, including around the Great Salt Lake.  The more localized nature of those sources makes them difficult to identify in satellite imagery that was available later in the afternoon.  

H/t to Dr. Derek Mallia and Dr. Maura Hahnenberger for e-mails contributing to this analysis.


  1. I took a motorcycle ride up LCC in clear air that evening. On the way down, I thought a fire had started in the valley when we caught a glimpse of it. The wind and dust was insane, i don't recall getting these dust storms from NW winds as much as we usually do from S-SW wind events. In other news, somebody's dog was running up the middle of the road at us from the Lisa Falls trailhead. Not a hazard i was expecting during this ride...

    1. We get more dust from S-SW wind events, but NW can also produce. The NW events tend to be quick hitters, although the dust concentrations can be very high immediately following frontal passage.