Friday, January 18, 2013

And Then Depression Set In....

That quote, uttered by Bill Murray character John Wingo in the Oscar-snubbed film Stripes, pretty much sums up the situation this morning.

The upper-air sounding from this morning shows little change compared to yesterday.  We are capped under a very strong inversion in which temperatures increase from -13.1ºC at 5933 ft to 0.0ºC at 7534 ft.

In the Salt Lake Valley, particulate matter concentrations continue to climb.  The eclipsed the National Ambient Air Quality Standard for PM2.5 yesterday and now sit at 47.5 ug/m3.

Source: Utah Division of Air Quality
The one silver lining in this event (if there is one) is that the base of the inversion is still elevated.  As a result, emissions are mixing through a layer that is about 1700 ft deep, which probably helps keep concentrations a bit lower than they would be if the inversion where based at the valley floor, as sometimes occurs during inversion events.

We're stuck with this until at least Tuesday.  Forecasts for mid week vary in the intensity and timing of an approaching trough, so we're just going to have to see in a couple of days if there's any hope of busting this thing out.

As is usually the case during inversions, the weather is spectacular in the mountains.  High temperatures yesterday at the base of Alta were in the 40s.  Escape and enjoy.


  1. Meteorologically speaking, the effective height of the terrain surrounding the greater Salt Lake Basin is something like 6,000 feet MSL (with limited terrain gaps below this), generally confining the cold pool up to that elevation. So as long as there is essentially no synoptic scale pressure gradient, I suspect the primary inverted layer here at SLC might remain near to above this level with at least daytime mixing to around the 6,000 foot level. If we end up near or west of the ridge axis (perhaps early next week), associated with falling pressure to our north and west, that could cause the inversion height to come down as cold pool shifts a bit within the basin. Will be interesting... not very optimistic about much mixing next week though.

  2. Good illustration of the degree of cold pooling on 20Z surface obs... Vernal vs Denver, essentially same elevation and under the same synoptic scale air mass. Vernal at 1 degree F, Denver at a nice 55 F.

  3. WOW just looked at the pm 2.5 it hit 97.5 today, check it out