Friday, December 21, 2012

A Look at Utah Cold Pools

Warmer air has moved in aloft, but most of the valleys and basins of northern Utah remained mired in cold pools (a.k.a. inversions) that simply will not scour out.  This morning's sounding from the Salt Lake City airport shows a surface temperature of 26ºF (-3ºC), but aloft, temperatures peak at about 37ºF (3ºC) about a kilometer above the valley floor.  Surface winds within the cold pool are light, but there is a 35 knot jet sitting about 1500 feet above the valley floor.

It's colder elsewhere.  Here's some overnight minimum temperatures for you:

Salt Lake City International Airport: 20ºF
Provo Municipal Airport: 12ºF
Vernal: -5ºF (lowest hourly temperature reported, minimum may be lower)
Cedar City: 3ºF (lowest hourly temperature reported, minimum may be lower)
Bryce Canyon: -17ºF (lowest 5-min temperature reported, minimum may be lower)
Peter Sinks: -24ºF (lowest 15-min temperature reported, minimum may be lower)

The evolution of the cold pool at Cedar City is quite interesting.  They observed their coldest temperatures in the early morning hours on Thursday.  This morning was actually quite a bit warmer.  Then, this morning, the cold pool mixed out nearly instantaneously, and the temperature rose from 3.2ºF to 28.4ºF in 40 min.

I think it will be interesting to see what happens today in the Salt Lake Valley.  Perhaps the strong flow aloft will scour out the cold pool from the top down, resulting in warmer temperatures on the benches while the valley floor remains colder.  We often see this in situations like this.  If it's not going to snow, we may as well tap into that warmer (and less polluted) air.


  1. I heard the wind suddenly pick up in a serious way here at my house this evening, and looking at Mesowest I see that Salt Lake Valley has mixed out down to about 4500 feet, probably the best mixing of any lower valley area in the state. A couple of sites in Sandy and Draper have spiked to between 40 and 50 degrees F, if the data are correct. Most of western Utah remains inverted to between 5000 and 6000 feet judging from Mesowest stations, while eastern Utah seems to have a massive cold pool up to 8,000 feet or higher, locked in place by the terrain of the Uintas and Wasatch. The NAM even shows a large surface pressure gradient across the Wasatch Range with the cold air banked up against the eastern side.

  2. I know that I have posted a lot on this topic, but today was an excellent day to observe the structure of the remaining cold pool over the Salt Lake Basin. Driving up along I-15 and I-84 there was not a lot else to do. Areas on the eastern side of the basin, along the I-15 corridor from SLC to Brigham City, were mixed out right down to lake level early this afternoon. The cold pool was visible as a distinct hazy layer in the sun, starting as a very shallow wedge just west of SLC and gradually increasing in depth to the west and north. It reached at least the 6,000 foot level on the opposite side of the basin. There appeared to be some large wave-like features that barely reached the cold pool's LCL in the distant western portion of the basin (perhaps as high as the 8,000 foot level based on dew point obs), and briefly a few tiny cumulus as well near the Raft River Mountains in far northwest Utah. This may help to explain why some areas such as Wendover are still so cold, and why some of these valley areas can be quite snowy in warm sector storm periods which SLC usually is not.